diff --git a/exercises/09_GPS_Time/README.md b/exercises/09_GPS_Time/README.md
deleted file mode 100644
index a8a1a81..0000000
--- a/exercises/09_GPS_Time/README.md
+++ /dev/null
@@ -1,49 +0,0 @@
-## Exercise 09: GPS Time (L76K)
-
-This exercise boots the T-Beam Supreme and verifies GPS behavior at startup.
-
-Important sequence note:
-
-- Exercise 10 (`10_Simple_GPS`) should be completed before this exercise.
-- Exercise 10 README contains the detailed pin-configuration explanation and troubleshooting rationale for why explicit GPS pin mapping is critical on this hardware.
-- If GPS behavior is unexpected here, review Exercise 10 README first, then return to Exercise 9.
-
-Implemented behavior:
-
-1. Initializes PMU, OLED, and SD startup watcher (same startup SD path used in Exercise 08).
-2. Probes GPS at startup for NMEA traffic, module identity, satellite count, and UTC time availability.
-   - Uses explicit GPS UART pins and an active startup probe (multi-baud + common GPS query commands), aligned with the approach validated in Exercise 10.
-3. If L76K is detected, normal GPS-time flow continues.
-4. If L76K is not detected and Quectel-style module text is detected, OLED shows a hard TODO error:
-   - Quectel detected
-   - L76K required
-   - Quectel support is TODO
-5. Every minute:
-   - If GPS UTC is valid: shows GPS UTC time and satellites on OLED.
-   - If satellites are seen but UTC is not valid yet: shows that condition and RTC time.
-   - If no satellites: shows:
-     - "Unable to acquire"
-     - "satellites"
-     - "Take me outside so I"
-     - "can see satellites"
-     - plus current RTC time.
-
-Notes:
-
-- GPS time displayed is UTC from NMEA RMC with valid status.
-- Satellite count uses best available from GGA/GSV.
-- RTC fallback reads PCF8563 via Wire1.
-
-## Build
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a
-```
-
-## Upload
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a -t upload --upload-port /dev/ttyACM0
-```
diff --git a/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.cpp b/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.cpp
deleted file mode 100644
index 1e8791c..0000000
--- a/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.cpp
+++ /dev/null
@@ -1,360 +0,0 @@
-#include "StartupSdManager.h"
-
-#include <stdarg.h>
-#include "driver/gpio.h"
-
-StartupSdManager::StartupSdManager(Print& serial) : serial_(serial) {}
-
-bool StartupSdManager::begin(const SdWatcherConfig& cfg, SdStatusCallback callback) {
-  cfg_ = cfg;
-  callback_ = callback;
-
-  forceSpiDeselected();
-  dumpSdPins("very-early");
-
-  if (!initPmuForSdPower()) {
-    return false;
-  }
-
-  cycleSdRail();
-  delay(cfg_.startupWarmupMs);
-
-  bool warmMounted = false;
-  for (uint8_t i = 0; i < 3; ++i) {
-    if (mountPreferred(false)) {
-      warmMounted = true;
-      break;
-    }
-    delay(200);
-  }
-
-  // Some cards need a longer power/settle window after cold boot.
-  // Before declaring ABSENT, retry with extended settle and a full scan.
-  if (!warmMounted) {
-    logf("Watcher: startup preferred mount failed, retrying with extended settle");
-    cycleSdRail(400, 1200);
-    delay(cfg_.startupWarmupMs + 1500);
-    warmMounted = mountCardFullScan();
-  }
-
-  if (warmMounted) {
-    setStateMounted();
-  } else {
-    setStateAbsent();
-  }
-  return true;
-}
-
-void StartupSdManager::update() {
-  const uint32_t now = millis();
-  const uint32_t pollInterval =
-      (watchState_ == SdWatchState::MOUNTED) ? cfg_.pollIntervalMountedMs : cfg_.pollIntervalAbsentMs;
-
-  if ((uint32_t)(now - lastPollMs_) < pollInterval) {
-    return;
-  }
-  lastPollMs_ = now;
-
-  if (watchState_ == SdWatchState::MOUNTED) {
-    if (verifyMountedCard()) {
-      presentVotes_ = 0;
-      absentVotes_ = 0;
-      return;
-    }
-
-    if (mountPreferred(false) && verifyMountedCard()) {
-      presentVotes_ = 0;
-      absentVotes_ = 0;
-      return;
-    }
-
-    absentVotes_++;
-    presentVotes_ = 0;
-    if (absentVotes_ >= cfg_.votesToAbsent) {
-      setStateAbsent();
-      absentVotes_ = 0;
-    }
-    return;
-  }
-
-  bool mounted = mountPreferred(false);
-  if (!mounted && (uint32_t)(now - lastFullScanMs_) >= cfg_.fullScanIntervalMs) {
-    lastFullScanMs_ = now;
-    if (cfg_.recoveryRailCycleOnFullScan) {
-      logf("Watcher: recovery rail cycle before full scan");
-      cycleSdRail(cfg_.recoveryRailOffMs, cfg_.recoveryRailOnSettleMs);
-      delay(150);
-    }
-    logf("Watcher: preferred probe failed, running full scan");
-    mounted = mountCardFullScan();
-  }
-
-  if (mounted) {
-    presentVotes_++;
-    absentVotes_ = 0;
-    if (presentVotes_ >= cfg_.votesToPresent) {
-      setStateMounted();
-      presentVotes_ = 0;
-    }
-  } else {
-    absentVotes_++;
-    presentVotes_ = 0;
-    if (absentVotes_ >= cfg_.votesToAbsent) {
-      setStateAbsent();
-      absentVotes_ = 0;
-    }
-  }
-}
-
-bool StartupSdManager::consumeMountedEvent() {
-  bool out = mountedEventPending_;
-  mountedEventPending_ = false;
-  return out;
-}
-
-bool StartupSdManager::consumeRemovedEvent() {
-  bool out = removedEventPending_;
-  removedEventPending_ = false;
-  return out;
-}
-
-void StartupSdManager::logf(const char* fmt, ...) {
-  char msg[196];
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(msg, sizeof(msg), fmt, args);
-  va_end(args);
-  serial_.printf("[%10lu][%06lu] %s\r\n",
-                 (unsigned long)millis(),
-                 (unsigned long)logSeq_++,
-                 msg);
-}
-
-void StartupSdManager::notify(SdEvent event, const char* message) {
-  if (callback_ != nullptr) {
-    callback_(event, message);
-  }
-}
-
-void StartupSdManager::forceSpiDeselected() {
-  pinMode(tbeam_supreme::sdCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::sdCs(), HIGH);
-  pinMode(tbeam_supreme::imuCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::imuCs(), HIGH);
-}
-
-void StartupSdManager::dumpSdPins(const char* tag) {
-  if (!cfg_.enablePinDumps) {
-    (void)tag;
-    return;
-  }
-
-  const gpio_num_t cs = (gpio_num_t)tbeam_supreme::sdCs();
-  const gpio_num_t sck = (gpio_num_t)tbeam_supreme::sdSck();
-  const gpio_num_t miso = (gpio_num_t)tbeam_supreme::sdMiso();
-  const gpio_num_t mosi = (gpio_num_t)tbeam_supreme::sdMosi();
-  logf("PINS(%s): CS=%d SCK=%d MISO=%d MOSI=%d",
-       tag, gpio_get_level(cs), gpio_get_level(sck), gpio_get_level(miso), gpio_get_level(mosi));
-}
-
-bool StartupSdManager::initPmuForSdPower() {
-  if (!tbeam_supreme::initPmuForPeripherals(pmu_, &serial_)) {
-    logf("ERROR: PMU init failed");
-    return false;
-  }
-  return true;
-}
-
-void StartupSdManager::cycleSdRail(uint32_t offMs, uint32_t onSettleMs) {
-  if (!cfg_.enableSdRailCycle) {
-    return;
-  }
-  if (!pmu_) {
-    logf("SD rail cycle skipped: pmu=null");
-    return;
-  }
-
-  forceSpiDeselected();
-  pmu_->disablePowerOutput(XPOWERS_BLDO1);
-  delay(offMs);
-  pmu_->setPowerChannelVoltage(XPOWERS_BLDO1, 3300);
-  pmu_->enablePowerOutput(XPOWERS_BLDO1);
-  delay(onSettleMs);
-}
-
-bool StartupSdManager::tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz, bool verbose) {
-  SD.end();
-  bus.end();
-  delay(10);
-  forceSpiDeselected();
-
-  bus.begin(tbeam_supreme::sdSck(), tbeam_supreme::sdMiso(), tbeam_supreme::sdMosi(), tbeam_supreme::sdCs());
-  digitalWrite(tbeam_supreme::sdCs(), HIGH);
-  delay(2);
-  for (int i = 0; i < 10; i++) {
-    bus.transfer(0xFF);
-  }
-  delay(2);
-
-  if (verbose) {
-    logf("SD: trying bus=%s freq=%lu Hz", busName, (unsigned long)hz);
-  }
-
-  if (!SD.begin(tbeam_supreme::sdCs(), bus, hz)) {
-    if (verbose) {
-      logf("SD: mount failed (possible non-FAT format, power, or bus issue)");
-    }
-    return false;
-  }
-
-  if (SD.cardType() == CARD_NONE) {
-    SD.end();
-    return false;
-  }
-
-  sdSpi_ = &bus;
-  sdBusName_ = busName;
-  sdFreq_ = hz;
-  return true;
-}
-
-bool StartupSdManager::mountPreferred(bool verbose) {
-  return tryMountWithBus(sdSpiH_, "HSPI", 400000, verbose);
-}
-
-bool StartupSdManager::mountCardFullScan() {
-  const uint32_t freqs[] = {400000, 1000000, 4000000, 10000000};
-
-  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
-    if (tryMountWithBus(sdSpiH_, "HSPI", freqs[i], true)) {
-      logf("SD: card detected and mounted");
-      return true;
-    }
-  }
-  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
-    if (tryMountWithBus(sdSpiF_, "FSPI", freqs[i], true)) {
-      logf("SD: card detected and mounted");
-      return true;
-    }
-  }
-
-  logf("SD: begin() failed on all bus/frequency attempts");
-  return false;
-}
-
-bool StartupSdManager::verifyMountedCard() {
-  File root = SD.open("/", FILE_READ);
-  if (!root) {
-    return false;
-  }
-  root.close();
-  return true;
-}
-
-const char* StartupSdManager::cardTypeToString(uint8_t type) {
-  switch (type) {
-    case CARD_MMC:
-      return "MMC";
-    case CARD_SD:
-      return "SDSC";
-    case CARD_SDHC:
-      return "SDHC/SDXC";
-    default:
-      return "UNKNOWN";
-  }
-}
-
-void StartupSdManager::printCardInfo() {
-  uint8_t cardType = SD.cardType();
-  uint64_t cardSizeMB = SD.cardSize() / (1024ULL * 1024ULL);
-  uint64_t totalMB = SD.totalBytes() / (1024ULL * 1024ULL);
-  uint64_t usedMB = SD.usedBytes() / (1024ULL * 1024ULL);
-
-  logf("SD type: %s", cardTypeToString(cardType));
-  logf("SD size: %llu MB", cardSizeMB);
-  logf("FS total: %llu MB", totalMB);
-  logf("FS used : %llu MB", usedMB);
-  logf("SPI bus: %s @ %lu Hz", sdBusName_, (unsigned long)sdFreq_);
-}
-
-bool StartupSdManager::ensureDirRecursive(const char* path) {
-  String full(path);
-  if (!full.startsWith("/")) {
-    full = "/" + full;
-  }
-
-  int start = 1;
-  while (start > 0 && start < (int)full.length()) {
-    int slash = full.indexOf('/', start);
-    String partial = (slash < 0) ? full : full.substring(0, slash);
-    if (!SD.exists(partial.c_str()) && !SD.mkdir(partial.c_str())) {
-      logf("ERROR: mkdir failed for %s", partial.c_str());
-      return false;
-    }
-    if (slash < 0) {
-      break;
-    }
-    start = slash + 1;
-  }
-
-  return true;
-}
-
-bool StartupSdManager::rewriteFile(const char* path, const char* payload) {
-  if (SD.exists(path) && !SD.remove(path)) {
-    logf("ERROR: failed to erase %s", path);
-    return false;
-  }
-
-  File f = SD.open(path, FILE_WRITE);
-  if (!f) {
-    logf("ERROR: failed to create %s", path);
-    return false;
-  }
-
-  size_t wrote = f.println(payload);
-  f.close();
-  if (wrote == 0) {
-    logf("ERROR: write failed for %s", path);
-    return false;
-  }
-  return true;
-}
-
-void StartupSdManager::permissionsDemo(const char* path) {
-  logf("Permissions demo: FAT has no Unix chmod/chown, use open mode only.");
-  File r = SD.open(path, FILE_READ);
-  if (!r) {
-    logf("Could not open %s as FILE_READ", path);
-    return;
-  }
-  size_t writeInReadMode = r.print("attempt write while opened read-only");
-  if (writeInReadMode == 0) {
-    logf("As expected, FILE_READ write was blocked.");
-  } else {
-    logf("NOTE: FILE_READ write returned %u (unexpected)", (unsigned)writeInReadMode);
-  }
-  r.close();
-}
-
-void StartupSdManager::setStateMounted() {
-  if (watchState_ != SdWatchState::MOUNTED) {
-    logf("EVENT: card inserted/mounted");
-    mountedEventPending_ = true;
-    notify(SdEvent::CARD_MOUNTED, "SD card mounted");
-  }
-  watchState_ = SdWatchState::MOUNTED;
-}
-
-void StartupSdManager::setStateAbsent() {
-  if (watchState_ == SdWatchState::MOUNTED) {
-    logf("EVENT: card removed/unavailable");
-    removedEventPending_ = true;
-    notify(SdEvent::CARD_REMOVED, "SD card removed");
-  } else if (watchState_ != SdWatchState::ABSENT) {
-    logf("EVENT: no card detected");
-    notify(SdEvent::NO_CARD, "Missing SD card or invalid FAT16/FAT32 format");
-  }
-  SD.end();
-  watchState_ = SdWatchState::ABSENT;
-}
diff --git a/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.h b/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.h
deleted file mode 100644
index be9ef27..0000000
--- a/exercises/09_GPS_Time/lib/startup_sd/StartupSdManager.h
+++ /dev/null
@@ -1,90 +0,0 @@
-#pragma once
-
-#include <Arduino.h>
-#include <SD.h>
-#include <SPI.h>
-#include <Wire.h>
-#include "tbeam_supreme_adapter.h"
-
-enum class SdWatchState : uint8_t {
-  UNKNOWN = 0,
-  ABSENT,
-  MOUNTED
-};
-
-enum class SdEvent : uint8_t {
-  NO_CARD,
-  CARD_MOUNTED,
-  CARD_REMOVED
-};
-
-using SdStatusCallback = void (*)(SdEvent event, const char* message);
-
-struct SdWatcherConfig {
-  bool enableSdRailCycle = true;
-  bool enablePinDumps = true;
-  bool recoveryRailCycleOnFullScan = true;
-  uint32_t recoveryRailOffMs = 250;
-  uint32_t recoveryRailOnSettleMs = 700;
-  uint32_t startupWarmupMs = 1500;
-  uint32_t pollIntervalAbsentMs = 1000;
-  uint32_t pollIntervalMountedMs = 2000;
-  uint32_t fullScanIntervalMs = 10000;
-  uint8_t votesToPresent = 2;
-  uint8_t votesToAbsent = 5;
-};
-
-class StartupSdManager {
- public:
-  explicit StartupSdManager(Print& serial = Serial);
-
-  bool begin(const SdWatcherConfig& cfg, SdStatusCallback callback = nullptr);
-  void update();
-
-  bool isMounted() const { return watchState_ == SdWatchState::MOUNTED; }
-  SdWatchState state() const { return watchState_; }
-
-  bool consumeMountedEvent();
-  bool consumeRemovedEvent();
-
-  void printCardInfo();
-  bool ensureDirRecursive(const char* path);
-  bool rewriteFile(const char* path, const char* payload);
-  void permissionsDemo(const char* path);
-
- private:
-  void logf(const char* fmt, ...);
-  void notify(SdEvent event, const char* message);
-  void forceSpiDeselected();
-  void dumpSdPins(const char* tag);
-  bool initPmuForSdPower();
-  void cycleSdRail(uint32_t offMs = 250, uint32_t onSettleMs = 600);
-  bool tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz, bool verbose);
-  bool mountPreferred(bool verbose);
-  bool mountCardFullScan();
-  bool verifyMountedCard();
-  const char* cardTypeToString(uint8_t type);
-  void setStateMounted();
-  void setStateAbsent();
-
-  Print& serial_;
-  SdWatcherConfig cfg_{};
-  SdStatusCallback callback_ = nullptr;
-
-  SPIClass sdSpiH_{HSPI};
-  SPIClass sdSpiF_{FSPI};
-  SPIClass* sdSpi_ = nullptr;
-  const char* sdBusName_ = "none";
-  uint32_t sdFreq_ = 0;
-  XPowersLibInterface* pmu_ = nullptr;
-
-  SdWatchState watchState_ = SdWatchState::UNKNOWN;
-  uint8_t presentVotes_ = 0;
-  uint8_t absentVotes_ = 0;
-  uint32_t lastPollMs_ = 0;
-  uint32_t lastFullScanMs_ = 0;
-  uint32_t logSeq_ = 0;
-
-  bool mountedEventPending_ = false;
-  bool removedEventPending_ = false;
-};
diff --git a/exercises/09_GPS_Time/lib/startup_sd/library.json b/exercises/09_GPS_Time/lib/startup_sd/library.json
deleted file mode 100644
index 4978fdd..0000000
--- a/exercises/09_GPS_Time/lib/startup_sd/library.json
+++ /dev/null
@@ -1,12 +0,0 @@
-{
-  "name": "startup_sd",
-  "version": "0.1.0",
-  "dependencies": [
-    {
-      "name": "XPowersLib"
-    },
-    {
-      "name": "Wire"
-    }
-  ]
-}
diff --git a/exercises/09_GPS_Time/lib/system_startup/SystemStartup.cpp b/exercises/09_GPS_Time/lib/system_startup/SystemStartup.cpp
deleted file mode 100644
index 3a82e1f..0000000
--- a/exercises/09_GPS_Time/lib/system_startup/SystemStartup.cpp
+++ /dev/null
@@ -1,96 +0,0 @@
-#include "SystemStartup.h"
-
-#include <Wire.h>
-#include <U8g2lib.h>
-
-#ifndef OLED_SDA
-#define OLED_SDA 17
-#endif
-
-#ifndef OLED_SCL
-#define OLED_SCL 18
-#endif
-
-#ifndef OLED_ADDR
-#define OLED_ADDR 0x3C
-#endif
-
-static const bool kEnableOled = true;
-
-static U8G2_SH1106_128X64_NONAME_F_HW_I2C g_oled(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
-static SystemStartup* g_activeSystemStartup = nullptr;
-
-static void forceSpiDeselectedEarly() {
-  pinMode(tbeam_supreme::sdCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::sdCs(), HIGH);
-  pinMode(tbeam_supreme::imuCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::imuCs(), HIGH);
-}
-
-SystemStartup::SystemStartup(Print& serial) : serial_(serial), sd_(serial) {}
-
-bool SystemStartup::begin(const SystemStartupConfig& cfg, SystemEventCallback callback) {
-  cfg_ = cfg;
-  callback_ = callback;
-  g_activeSystemStartup = this;
-
-  // Match Exercise 05 behavior: deselect SPI devices immediately at startup.
-  forceSpiDeselectedEarly();
-
-  if (kEnableOled) {
-    Wire.begin(OLED_SDA, OLED_SCL);
-    g_oled.setI2CAddress(OLED_ADDR << 1);
-    g_oled.begin();
-  }
-
-  emit(SystemEvent::BOOTING, "System startup booting");
-  oledShow3("System Startup", "Booting...");
-
-  serial_.printf("Sleeping for %lu ms to allow Serial Monitor connection...\r\n",
-                 (unsigned long)cfg_.serialDelayMs);
-  delay(cfg_.serialDelayMs);
-
-  return sd_.begin(cfg_.sd, &SystemStartup::onSdEventThunk);
-}
-
-void SystemStartup::update() {
-  sd_.update();
-}
-
-void SystemStartup::onSdEventThunk(SdEvent event, const char* message) {
-  if (g_activeSystemStartup != nullptr) {
-    g_activeSystemStartup->onSdEvent(event, message);
-  }
-}
-
-void SystemStartup::onSdEvent(SdEvent event, const char* message) {
-  if (event == SdEvent::NO_CARD) {
-    oledShow3("SD missing or", "invalid FAT16/32", "Insert/format card");
-    emit(SystemEvent::SD_MISSING, message);
-  } else if (event == SdEvent::CARD_MOUNTED) {
-    oledShow3("SD card ready", "Mounted OK");
-    emit(SystemEvent::SD_READY, message);
-  } else if (event == SdEvent::CARD_REMOVED) {
-    oledShow3("SD card removed", "Please re-insert");
-    emit(SystemEvent::SD_REMOVED, message);
-  }
-}
-
-void SystemStartup::emit(SystemEvent event, const char* message) {
-  serial_.printf("[SYSTEM] %s\r\n", message);
-  if (callback_ != nullptr) {
-    callback_(event, message);
-  }
-}
-
-void SystemStartup::oledShow3(const char* l1, const char* l2, const char* l3) {
-  if (!kEnableOled) {
-    return;
-  }
-  g_oled.clearBuffer();
-  g_oled.setFont(u8g2_font_6x10_tf);
-  if (l1) g_oled.drawUTF8(0, 16, l1);
-  if (l2) g_oled.drawUTF8(0, 32, l2);
-  if (l3) g_oled.drawUTF8(0, 48, l3);
-  g_oled.sendBuffer();
-}
diff --git a/exercises/09_GPS_Time/lib/system_startup/SystemStartup.h b/exercises/09_GPS_Time/lib/system_startup/SystemStartup.h
deleted file mode 100644
index cd83857..0000000
--- a/exercises/09_GPS_Time/lib/system_startup/SystemStartup.h
+++ /dev/null
@@ -1,46 +0,0 @@
-#pragma once
-
-#include <Arduino.h>
-#include "StartupSdManager.h"
-
-// Convenience alias so sketches can use System.println(...) style logging.
-// Arduino exposes Serial, not System, so map System -> Serial.
-#ifndef System
-#define System Serial
-#endif
-
-enum class SystemEvent : uint8_t {
-  BOOTING = 0,
-  SD_MISSING,
-  SD_READY,
-  SD_REMOVED
-};
-
-using SystemEventCallback = void (*)(SystemEvent event, const char* message);
-
-struct SystemStartupConfig {
-  uint32_t serialDelayMs = 5000;
-  SdWatcherConfig sd{};
-};
-
-class SystemStartup {
- public:
-  explicit SystemStartup(Print& serial = Serial);
-
-  bool begin(const SystemStartupConfig& cfg = SystemStartupConfig{}, SystemEventCallback callback = nullptr);
-  void update();
-
-  bool isSdMounted() const { return sd_.isMounted(); }
-  StartupSdManager& sdManager() { return sd_; }
-
- private:
-  static void onSdEventThunk(SdEvent event, const char* message);
-  void onSdEvent(SdEvent event, const char* message);
-  void emit(SystemEvent event, const char* message);
-  void oledShow3(const char* l1, const char* l2 = nullptr, const char* l3 = nullptr);
-
-  Print& serial_;
-  SystemStartupConfig cfg_{};
-  SystemEventCallback callback_ = nullptr;
-  StartupSdManager sd_;
-};
diff --git a/exercises/09_GPS_Time/lib/system_startup/library.json b/exercises/09_GPS_Time/lib/system_startup/library.json
deleted file mode 100644
index 0c2c1cf..0000000
--- a/exercises/09_GPS_Time/lib/system_startup/library.json
+++ /dev/null
@@ -1,15 +0,0 @@
-{
-  "name": "system_startup",
-  "version": "0.1.0",
-  "dependencies": [
-    {
-      "name": "startup_sd"
-    },
-    {
-      "name": "U8g2"
-    },
-    {
-      "name": "Wire"
-    }
-  ]
-}
diff --git a/exercises/09_GPS_Time/platformio.ini b/exercises/09_GPS_Time/platformio.ini
deleted file mode 100644
index fff0d30..0000000
--- a/exercises/09_GPS_Time/platformio.ini
+++ /dev/null
@@ -1,41 +0,0 @@
-; 20260213 ChatGPT
-; $Id$
-; $HeadURL$
-
-[platformio]
-default_envs = node_a
-
-[env]
-platform = espressif32
-framework = arduino
-board = esp32-s3-devkitc-1
-monitor_speed = 115200
-lib_deps =
-  lewisxhe/XPowersLib@0.3.3
-  Wire
-  olikraus/U8g2@^2.36.4
-
-; SD pins based on T-Beam S3 core pin mapping
-build_flags =
-  -I ../../shared/boards
-  -I ../../external/microReticulum_Firmware
-  -D BOARD_MODEL=BOARD_TBEAM_S_V1
-  -D OLED_SDA=17
-  -D OLED_SCL=18
-  -D OLED_ADDR=0x3C
-  -D GPS_RX_PIN=9
-  -D GPS_TX_PIN=8
-  -D GPS_WAKEUP_PIN=7
-  -D GPS_1PPS_PIN=6
-  -D ARDUINO_USB_MODE=1
-  -D ARDUINO_USB_CDC_ON_BOOT=1
-
-[env:node_a]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"A\"
-
-[env:node_b]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"B\"
diff --git a/exercises/09_GPS_Time/src/main.cpp b/exercises/09_GPS_Time/src/main.cpp
deleted file mode 100644
index 36b0624..0000000
--- a/exercises/09_GPS_Time/src/main.cpp
+++ /dev/null
@@ -1,556 +0,0 @@
-// 20260217 ChatGPT
-// $Id$
-// $HeadURL$
-
-#include <Arduino.h>
-#include <Wire.h>
-#include <U8g2lib.h>
-
-#include "StartupSdManager.h"
-#include "tbeam_supreme_adapter.h"
-
-#ifndef OLED_SDA
-#define OLED_SDA 17
-#endif
-
-#ifndef OLED_SCL
-#define OLED_SCL 18
-#endif
-
-#ifndef OLED_ADDR
-#define OLED_ADDR 0x3C
-#endif
-
-#ifndef RTC_I2C_ADDR
-#define RTC_I2C_ADDR 0x51
-#endif
-
-#ifndef GPS_BAUD
-#define GPS_BAUD 9600
-#endif
-
-static const uint32_t kSerialDelayMs = 5000;
-static const uint32_t kGpsStartupProbeMs = 20000;
-static const uint32_t kMinuteMs = 60000;
-
-static XPowersLibInterface* g_pmu = nullptr;
-static StartupSdManager g_sd(Serial);
-static U8G2_SH1106_128X64_NONAME_F_HW_I2C g_oled(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
-static HardwareSerial g_gpsSerial(1);
-
-static uint32_t g_logSeq = 0;
-static uint32_t g_lastMinuteReportMs = 0;
-static uint32_t g_gpsBaud = GPS_BAUD;
-
-static bool g_prevHadSatellites = false;
-static bool g_prevHadValidUtc = false;
-static bool g_satellitesAcquiredAnnounced = false;
-static bool g_timeAcquiredAnnounced = false;
-
-static char g_gpsLine[128];
-static size_t g_gpsLineLen = 0;
-
-enum class GpsModuleKind : uint8_t {
-  UNKNOWN = 0,
-  L76K,
-  QUECTEL_TODO
-};
-
-struct RtcDateTime {
-  uint16_t year;
-  uint8_t month;
-  uint8_t day;
-  uint8_t hour;
-  uint8_t minute;
-  uint8_t second;
-};
-
-struct GpsState {
-  GpsModuleKind module = GpsModuleKind::UNKNOWN;
-  bool sawAnySentence = false;
-
-  uint8_t satsUsed = 0;
-  uint8_t satsInView = 0;
-
-  bool hasValidUtc = false;
-  uint16_t utcYear = 0;
-  uint8_t utcMonth = 0;
-  uint8_t utcDay = 0;
-  uint8_t utcHour = 0;
-  uint8_t utcMinute = 0;
-  uint8_t utcSecond = 0;
-};
-
-static GpsState g_gps;
-
-static void logf(const char* fmt, ...) {
-  char msg[220];
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(msg, sizeof(msg), fmt, args);
-  va_end(args);
-  Serial.printf("[%10lu][%06lu] %s\r\n", (unsigned long)millis(), (unsigned long)g_logSeq++, msg);
-}
-
-static void oledShowLines(const char* l1,
-                          const char* l2 = nullptr,
-                          const char* l3 = nullptr,
-                          const char* l4 = nullptr,
-                          const char* l5 = nullptr) {
-  g_oled.clearBuffer();
-  g_oled.setFont(u8g2_font_5x8_tf);
-  if (l1) g_oled.drawUTF8(0, 12, l1);
-  if (l2) g_oled.drawUTF8(0, 24, l2);
-  if (l3) g_oled.drawUTF8(0, 36, l3);
-  if (l4) g_oled.drawUTF8(0, 48, l4);
-  if (l5) g_oled.drawUTF8(0, 60, l5);
-  g_oled.sendBuffer();
-}
-
-static uint8_t fromBcd(uint8_t b) {
-  return ((b >> 4U) * 10U) + (b & 0x0FU);
-}
-
-static bool rtcRead(RtcDateTime& out, bool& lowVoltageFlag) {
-  Wire1.beginTransmission(RTC_I2C_ADDR);
-  Wire1.write(0x02);
-  if (Wire1.endTransmission(false) != 0) {
-    return false;
-  }
-
-  const uint8_t need = 7;
-  uint8_t got = Wire1.requestFrom((int)RTC_I2C_ADDR, (int)need);
-  if (got != need) {
-    return false;
-  }
-
-  uint8_t sec = Wire1.read();
-  uint8_t min = Wire1.read();
-  uint8_t hour = Wire1.read();
-  uint8_t day = Wire1.read();
-  (void)Wire1.read();  // weekday
-  uint8_t month = Wire1.read();
-  uint8_t year = Wire1.read();
-
-  lowVoltageFlag = (sec & 0x80U) != 0;
-  out.second = fromBcd(sec & 0x7FU);
-  out.minute = fromBcd(min & 0x7FU);
-  out.hour = fromBcd(hour & 0x3FU);
-  out.day = fromBcd(day & 0x3FU);
-  out.month = fromBcd(month & 0x1FU);
-  uint8_t yy = fromBcd(year);
-  bool century = (month & 0x80U) != 0;
-  out.year = century ? (1900U + yy) : (2000U + yy);
-  return true;
-}
-
-static String formatRtcNow() {
-  RtcDateTime now{};
-  bool lowV = false;
-  if (!rtcRead(now, lowV)) {
-    return "RTC: read failed";
-  }
-
-  char buf[48];
-  snprintf(buf,
-           sizeof(buf),
-           "RTC %04u-%02u-%02u %02u:%02u:%02u%s",
-           (unsigned)now.year,
-           (unsigned)now.month,
-           (unsigned)now.day,
-           (unsigned)now.hour,
-           (unsigned)now.minute,
-           (unsigned)now.second,
-           lowV ? " !LOWV" : "");
-  return String(buf);
-}
-
-static String gpsModuleToString(GpsModuleKind kind) {
-  if (kind == GpsModuleKind::L76K) {
-    return "L76K";
-  }
-  if (kind == GpsModuleKind::QUECTEL_TODO) {
-    return "Quectel/TODO";
-  }
-  return "Unknown";
-}
-
-static bool parseUInt2(const char* s, uint8_t& out) {
-  if (!s || !isdigit((unsigned char)s[0]) || !isdigit((unsigned char)s[1])) {
-    return false;
-  }
-  out = (uint8_t)((s[0] - '0') * 10 + (s[1] - '0'));
-  return true;
-}
-
-static void detectModuleFromText(const char* text) {
-  if (!text || text[0] == '\0') {
-    return;
-  }
-
-  String t(text);
-  t.toUpperCase();
-
-  if (t.indexOf("L76K") >= 0) {
-    g_gps.module = GpsModuleKind::L76K;
-    return;
-  }
-
-  if (t.indexOf("QUECTEL") >= 0 || t.indexOf("2021-10-20") >= 0 || t.indexOf("2021/10/20") >= 0) {
-    if (g_gps.module != GpsModuleKind::L76K) {
-      g_gps.module = GpsModuleKind::QUECTEL_TODO;
-    }
-  }
-}
-
-static void parseGga(char* fields[], int count) {
-  if (count <= 7) {
-    return;
-  }
-  int sats = atoi(fields[7]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsUsed = (uint8_t)sats;
-  }
-}
-
-static void parseGsv(char* fields[], int count) {
-  if (count <= 3) {
-    return;
-  }
-  int sats = atoi(fields[3]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsInView = (uint8_t)sats;
-  }
-}
-
-static void parseRmc(char* fields[], int count) {
-  if (count <= 9) {
-    return;
-  }
-
-  const char* utc = fields[1];
-  const char* status = fields[2];
-  const char* date = fields[9];
-
-  if (!status || status[0] != 'A') {
-    return;
-  }
-
-  if (!utc || strlen(utc) < 6 || !date || strlen(date) < 6) {
-    return;
-  }
-
-  uint8_t hh = 0, mm = 0, ss = 0;
-  uint8_t dd = 0, mo = 0, yy = 0;
-  if (!parseUInt2(utc + 0, hh) || !parseUInt2(utc + 2, mm) || !parseUInt2(utc + 4, ss)) {
-    return;
-  }
-  if (!parseUInt2(date + 0, dd) || !parseUInt2(date + 2, mo) || !parseUInt2(date + 4, yy)) {
-    return;
-  }
-
-  g_gps.utcHour = hh;
-  g_gps.utcMinute = mm;
-  g_gps.utcSecond = ss;
-  g_gps.utcDay = dd;
-  g_gps.utcMonth = mo;
-  g_gps.utcYear = (uint16_t)(2000U + yy);
-  g_gps.hasValidUtc = true;
-}
-
-static void parseTxt(char* fields[], int count) {
-  if (count <= 4) {
-    return;
-  }
-  detectModuleFromText(fields[4]);
-}
-
-static void processNmeaLine(char* line) {
-  if (!line || line[0] != '$') {
-    return;
-  }
-  g_gps.sawAnySentence = true;
-
-  char* star = strchr(line, '*');
-  if (star) {
-    *star = '\0';
-  }
-
-  char* fields[24] = {0};
-  int count = 0;
-  char* saveptr = nullptr;
-  char* tok = strtok_r(line, ",", &saveptr);
-  while (tok && count < 24) {
-    fields[count++] = tok;
-    tok = strtok_r(nullptr, ",", &saveptr);
-  }
-  if (count <= 0 || !fields[0]) {
-    return;
-  }
-
-  const char* header = fields[0];
-  size_t n = strlen(header);
-  if (n < 6) {
-    return;
-  }
-  const char* type = header + (n - 3);
-
-  if (strcmp(type, "GGA") == 0) {
-    parseGga(fields, count);
-  } else if (strcmp(type, "GSV") == 0) {
-    parseGsv(fields, count);
-  } else if (strcmp(type, "RMC") == 0) {
-    parseRmc(fields, count);
-  } else if (strcmp(type, "TXT") == 0) {
-    parseTxt(fields, count);
-  }
-}
-
-static void pollGpsSerial() {
-  while (g_gpsSerial.available() > 0) {
-    char c = (char)g_gpsSerial.read();
-    if (c == '\r') {
-      continue;
-    }
-    if (c == '\n') {
-      if (g_gpsLineLen > 0) {
-        g_gpsLine[g_gpsLineLen] = '\0';
-        processNmeaLine(g_gpsLine);
-        g_gpsLineLen = 0;
-      }
-      continue;
-    }
-
-    if (g_gpsLineLen + 1 < sizeof(g_gpsLine)) {
-      g_gpsLine[g_gpsLineLen++] = c;
-    } else {
-      g_gpsLineLen = 0;
-    }
-  }
-}
-
-static void startGpsUart(uint32_t baud) {
-  g_gpsSerial.end();
-  delay(20);
-  g_gpsSerial.setRxBufferSize(1024);
-  g_gpsSerial.begin(baud, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
-  g_gpsBaud = baud;
-}
-
-static bool collectGpsTraffic(uint32_t windowMs, bool updateSd) {
-  uint32_t start = millis();
-  size_t bytesSeen = 0;
-  while ((uint32_t)(millis() - start) < windowMs) {
-    while (g_gpsSerial.available() > 0) {
-      (void)g_gpsSerial.read();
-      bytesSeen++;
-    }
-    pollGpsSerial();
-    if (updateSd) {
-      g_sd.update();
-    }
-    delay(2);
-  }
-  return bytesSeen > 0 || g_gps.sawAnySentence;
-}
-
-static bool probeGpsAtBaud(uint32_t baud) {
-  startGpsUart(baud);
-  logf("Probing GPS at %lu baud...", (unsigned long)baud);
-  if (collectGpsTraffic(700, true)) {
-    return true;
-  }
-
-  // Common commands for MTK/L76K and related chipsets.
-  g_gpsSerial.write("$PCAS06,0*1B\r\n");
-  g_gpsSerial.write("$PMTK605*31\r\n");
-  g_gpsSerial.write("$PQTMVERNO*58\r\n");
-  g_gpsSerial.write("$PMTK353,1,1,1,1,1*2A\r\n");
-  g_gpsSerial.write("$PMTK314,0,1,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n");
-
-  return collectGpsTraffic(1200, true);
-}
-
-static void initialGpsProbe() {
-  const uint32_t bauds[] = {GPS_BAUD, 115200, 38400, 57600, 19200};
-  for (size_t i = 0; i < sizeof(bauds) / sizeof(bauds[0]); ++i) {
-    if (probeGpsAtBaud(bauds[i])) {
-      logf("GPS traffic detected at %lu baud", (unsigned long)g_gpsBaud);
-      return;
-    }
-  }
-  logf("No GPS traffic detected during startup probe");
-}
-
-static uint8_t bestSatelliteCount() {
-  return (g_gps.satsUsed > g_gps.satsInView) ? g_gps.satsUsed : g_gps.satsInView;
-}
-
-static bool isUnsupportedQuectelMode() {
-  return g_gps.module == GpsModuleKind::QUECTEL_TODO;
-}
-
-static void reportStatusToSerial() {
-  uint8_t sats = bestSatelliteCount();
-  logf("GPS module: %s", gpsModuleToString(g_gps.module).c_str());
-  logf("GPS sentences seen: %s", g_gps.sawAnySentence ? "yes" : "no");
-  logf("GPS satellites: used=%u in-view=%u best=%u",
-       (unsigned)g_gps.satsUsed,
-       (unsigned)g_gps.satsInView,
-       (unsigned)sats);
-  logf("GPS can provide time from satellites: %s", g_gps.hasValidUtc ? "YES" : "NO");
-}
-
-static void maybeAnnounceGpsTransitions() {
-  if (isUnsupportedQuectelMode()) {
-    return;
-  }
-
-  uint8_t sats = bestSatelliteCount();
-  bool hasSats = sats > 0;
-  bool hasUtc = g_gps.hasValidUtc;
-
-  if (!g_satellitesAcquiredAnnounced && !g_prevHadSatellites && hasSats) {
-    String rtc = formatRtcNow();
-    char l2[28];
-    snprintf(l2, sizeof(l2), "Satellites: %u", (unsigned)sats);
-    oledShowLines("GPS acquired", l2, "Satellite lock found", "Waiting for UTC...", rtc.c_str());
-    logf("Transition: satellites acquired (%u)", (unsigned)sats);
-    g_satellitesAcquiredAnnounced = true;
-  }
-
-  if (!g_timeAcquiredAnnounced && !g_prevHadValidUtc && hasUtc) {
-    char line2[40];
-    char line3[28];
-    snprintf(line2,
-             sizeof(line2),
-             "%04u-%02u-%02u %02u:%02u:%02u",
-             (unsigned)g_gps.utcYear,
-             (unsigned)g_gps.utcMonth,
-             (unsigned)g_gps.utcDay,
-             (unsigned)g_gps.utcHour,
-             (unsigned)g_gps.utcMinute,
-             (unsigned)g_gps.utcSecond);
-    snprintf(line3, sizeof(line3), "Satellites: %u", (unsigned)sats);
-    oledShowLines("GPS UTC acquired", line2, line3, "Source: L76K");
-    logf("Transition: GPS UTC acquired: %s", line2);
-    g_timeAcquiredAnnounced = true;
-  }
-
-  g_prevHadSatellites = hasSats;
-  g_prevHadValidUtc = hasUtc;
-}
-
-static void drawMinuteStatus() {
-  if (isUnsupportedQuectelMode()) {
-    oledShowLines("GPS module mismatch", "Quectel detected", "L76K required", "TODO: implement", "Quectel support");
-    logf("GPS module mismatch: Quectel detected but this exercise currently supports only L76K (TODO)");
-    return;
-  }
-
-  uint8_t sats = bestSatelliteCount();
-  if (g_gps.hasValidUtc) {
-    char line2[40];
-    char line3[28];
-    snprintf(line2,
-             sizeof(line2),
-             "%04u-%02u-%02u %02u:%02u:%02u",
-             (unsigned)g_gps.utcYear,
-             (unsigned)g_gps.utcMonth,
-             (unsigned)g_gps.utcDay,
-             (unsigned)g_gps.utcHour,
-             (unsigned)g_gps.utcMinute,
-             (unsigned)g_gps.utcSecond);
-    snprintf(line3, sizeof(line3), "Satellites: %u", (unsigned)sats);
-    oledShowLines("GPS time (UTC)", line2, line3, "Source: L76K");
-    logf("GPS time (UTC): %s  satellites=%u", line2, (unsigned)sats);
-    return;
-  }
-
-  String rtc = formatRtcNow();
-  if (sats > 0) {
-    char line2[28];
-    snprintf(line2, sizeof(line2), "Satellites: %u", (unsigned)sats);
-    oledShowLines("GPS signal detected", line2, "GPS UTC not ready", "yet, using RTC", rtc.c_str());
-    logf("Satellites detected (%u) but GPS UTC not ready. %s", (unsigned)sats, rtc.c_str());
-  } else {
-    oledShowLines("Unable to acquire", "satellites", "Take me outside so I", "can see satellites", rtc.c_str());
-    logf("Unable to acquire satellites. %s", rtc.c_str());
-  }
-}
-
-void setup() {
-  Serial.begin(115200);
-  delay(kSerialDelayMs);
-
-  Serial.println("\r\n==================================================");
-  Serial.println("Exercise 09: GPS Time");
-  Serial.println("==================================================");
-
-  if (!tbeam_supreme::initPmuForPeripherals(g_pmu, &Serial)) {
-    logf("PMU init failed");
-  }
-
-  Wire.begin(OLED_SDA, OLED_SCL);
-  g_oled.setI2CAddress(OLED_ADDR << 1);
-  g_oled.begin();
-  oledShowLines("GPS Time exercise", "Booting...");
-
-  SdWatcherConfig sdCfg{};
-  if (!g_sd.begin(sdCfg, nullptr)) {
-    logf("SD startup manager begin() failed");
-  }
-
-#ifdef GPS_WAKEUP_PIN
-  // Keep wake pin neutral; avoid forcing an unknown standby state.
-  pinMode(GPS_WAKEUP_PIN, INPUT);
-#endif
-
-#ifdef GPS_1PPS_PIN
-  pinMode(GPS_1PPS_PIN, INPUT);
-#endif
-
-  startGpsUart(GPS_BAUD);
-  logf("GPS UART started: RX=%d TX=%d baud=%lu", GPS_RX_PIN, GPS_TX_PIN, (unsigned long)g_gpsBaud);
-  initialGpsProbe();
-
-  oledShowLines("GPS startup probe", "Checking satellites", "and GPS time...");
-
-  uint32_t probeStart = millis();
-  uint32_t lastProbeUiMs = 0;
-  while ((uint32_t)(millis() - probeStart) < kGpsStartupProbeMs) {
-    pollGpsSerial();
-    g_sd.update();
-
-    uint32_t now = millis();
-    if ((uint32_t)(now - lastProbeUiMs) >= 1000) {
-      lastProbeUiMs = now;
-      char l3[28];
-      char l4[30];
-      char l5[24];
-      snprintf(l3, sizeof(l3), "Sats: %u", (unsigned)bestSatelliteCount());
-      snprintf(l4, sizeof(l4), "Module: %s", gpsModuleToString(g_gps.module).c_str());
-      snprintf(l5, sizeof(l5), "NMEA:%s %lu", g_gps.sawAnySentence ? "yes" : "no", (unsigned long)g_gpsBaud);
-      oledShowLines("GPS startup probe", "Checking satellites", l3, l4, l5);
-    }
-    delay(10);
-  }
-
-  reportStatusToSerial();
-  g_prevHadSatellites = (bestSatelliteCount() > 0);
-  g_prevHadValidUtc = g_gps.hasValidUtc;
-  drawMinuteStatus();
-  g_lastMinuteReportMs = millis();
-}
-
-void loop() {
-  pollGpsSerial();
-  g_sd.update();
-  maybeAnnounceGpsTransitions();
-
-  uint32_t now = millis();
-  if ((uint32_t)(now - g_lastMinuteReportMs) >= kMinuteMs) {
-    g_lastMinuteReportMs = now;
-    drawMinuteStatus();
-  }
-}
diff --git a/exercises/10_Simple_GPS/README.md b/exercises/10_Simple_GPS/README.md
deleted file mode 100644
index 6fc5c73..0000000
--- a/exercises/10_Simple_GPS/README.md
+++ /dev/null
@@ -1,98 +0,0 @@
-## Exercise 10: Simple GPS (No SD)
-
-Goal: verify GPS satellite and UTC time acquisition on T-Beam Supreme using OLED-only status updates.
-
-## Current behavior
-
-1. Boots PMU, OLED, RTC, and GPS UART.
-2. Runs an active startup GPS probe (multi-baud + query commands) to detect GPS serial traffic.
-3. Every 30 seconds:
-   - Shows `Trying to locate satellites` + `NMEA seen: yes/no` + current RTC time.
-   - Continues parsing GPS NMEA data.
-   - If GPS UTC is valid, shows GPS UTC + satellite count + `NMEA seen: yes/no`.
-   - Otherwise shows `Take me outside` + `NMEA seen: yes/no` + RTC.
-4. No SD card logic is used in this exercise.
-
-## Walk-through: original approach and why
-
-Initial implementation used a minimal/simple GPS strategy:
-
-1. Power up PMU rails using the existing T-Beam adapter.
-2. Start `Serial1` at 9600 baud.
-3. Parse incoming NMEA (`GGA/GSV/RMC`) passively.
-4. Show periodic OLED status every 30 seconds.
-
-Why this was chosen:
-
-- It is the smallest path to validate basic GPS lock/time behavior.
-- It avoids introducing SD complexity while isolating GPS.
-- It is easy for field testing (OLED-first, battery-powered).
-
-## What was discovered by comparing with Meshtastic
-
-Meshtastic GPS handling is more defensive and hardware-aware in principle:
-
-1. It uses a board variant that provides explicit GPS pin mapping for the T-Beam Supreme path.
-2. It initializes GPS serial with explicit RX/TX pins and larger receive buffers.
-3. It performs active startup probing (commands + response checks), not only passive listening.
-4. It attempts detection across known module families and may try multiple serial settings.
-5. It manages GNSS-related power/standby states deliberately (rather than assuming default UART traffic immediately appears).
-
-## What differed in this exercise and likely caused the issue
-
-The first Exercise 10 version was built on `esp32-s3-devkitc-1` with conditional pin usage.
-
-- If GPS pin macros are not present, `Serial1` can start on default pins.
-- That can produce `NMEA seen: no` forever even outdoors, because firmware is listening on the wrong UART pins.
-
-## Corrections applied after Meshtastic review
-
-1. Added explicit GPS pin defines in `platformio.ini`:
-   - `GPS_RX_PIN=9`
-   - `GPS_TX_PIN=8`
-   - `GPS_WAKEUP_PIN=7`
-   - `GPS_1PPS_PIN=6`
-2. Forced UART startup using explicit RX/TX pins.
-3. Added startup multi-baud active probe and common GPS query commands.
-4. Added OLED `NMEA seen: yes/no` so field tests distinguish:
-   - `no sky fix yet` vs
-   - `no GPS serial traffic at all`.
-
-## Field Test Checklist
-
-1. Flash and reboot outdoors with clear sky view.
-2. Confirm the OLED updates every 30 seconds.
-3. Watch for this expected progression:
-   - `Trying to locate satellites` + `NMEA seen: no`
-   - then `Trying to locate satellites` + `NMEA seen: yes`
-   - then either:
-     - `GPS lock acquired` with UTC and satellite count, or
-     - `Take me outside` if no fix yet.
-4. Keep unit stationary for 2-5 minutes for first lock after cold start.
-
-Interpretation guide:
-
-- `NMEA seen: no`: likely UART/pin/baud/module-power communication issue.
-- `NMEA seen: yes` + no lock: GPS is talking, but no valid fix yet (sky view/time-to-first-fix issue).
-- `GPS lock acquired`: fix is valid; UTC and satellites are available from GPS.
-- RTC line updates every 30 seconds: loop is alive and retry cycle is running.
-
-If still failing:
-
-1. Capture serial log from boot through at least 2 full 30-second cycles.
-2. Note whether `NMEA seen` ever changes from `no` to `yes`.
-3. Record whether GPS startup probe reports traffic at any baud rate.
-
-## Build
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a
-```
-
-## Upload
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a -t upload --upload-port /dev/ttyACM0
-```
diff --git a/exercises/10_Simple_GPS/platformio.ini b/exercises/10_Simple_GPS/platformio.ini
deleted file mode 100644
index a183c3b..0000000
--- a/exercises/10_Simple_GPS/platformio.ini
+++ /dev/null
@@ -1,40 +0,0 @@
-; 20260217 ChatGPT
-; $Id$
-; $HeadURL$
-
-[platformio]
-default_envs = node_a
-
-[env]
-platform = espressif32
-framework = arduino
-board = esp32-s3-devkitc-1
-monitor_speed = 115200
-lib_deps =
-  lewisxhe/XPowersLib@0.3.3
-  Wire
-  olikraus/U8g2@^2.36.4
-
-build_flags =
-  -I ../../shared/boards
-  -I ../../external/microReticulum_Firmware
-  -D BOARD_MODEL=BOARD_TBEAM_S_V1
-  -D OLED_SDA=17
-  -D OLED_SCL=18
-  -D OLED_ADDR=0x3C
-  -D GPS_RX_PIN=9
-  -D GPS_TX_PIN=8
-  -D GPS_WAKEUP_PIN=7
-  -D GPS_1PPS_PIN=6
-  -D ARDUINO_USB_MODE=1
-  -D ARDUINO_USB_CDC_ON_BOOT=1
-
-[env:node_a]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"A\"
-
-[env:node_b]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"B\"
diff --git a/exercises/10_Simple_GPS/src/main.cpp b/exercises/10_Simple_GPS/src/main.cpp
deleted file mode 100644
index 7456125..0000000
--- a/exercises/10_Simple_GPS/src/main.cpp
+++ /dev/null
@@ -1,431 +0,0 @@
-// 20260217 ChatGPT
-// $Id$
-// $HeadURL$
-
-#include <Arduino.h>
-#include <Wire.h>
-#include <U8g2lib.h>
-
-#include "tbeam_supreme_adapter.h"
-
-#ifndef OLED_SDA
-#define OLED_SDA 17
-#endif
-
-#ifndef OLED_SCL
-#define OLED_SCL 18
-#endif
-
-#ifndef OLED_ADDR
-#define OLED_ADDR 0x3C
-#endif
-
-#ifndef RTC_I2C_ADDR
-#define RTC_I2C_ADDR 0x51
-#endif
-
-#ifndef GPS_BAUD
-#define GPS_BAUD 9600
-#endif
-
-static const uint32_t kSerialDelayMs = 5000;
-static const uint32_t kReportIntervalMs = 30000;
-
-static XPowersLibInterface* g_pmu = nullptr;
-static U8G2_SH1106_128X64_NONAME_F_HW_I2C g_oled(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
-static HardwareSerial g_gpsSerial(1);
-
-static uint32_t g_logSeq = 0;
-static uint32_t g_lastReportMs = 0;
-static uint32_t g_gpsBaud = GPS_BAUD;
-
-static char g_gpsLine[128];
-static size_t g_gpsLineLen = 0;
-
-struct RtcDateTime {
-  uint16_t year;
-  uint8_t month;
-  uint8_t day;
-  uint8_t hour;
-  uint8_t minute;
-  uint8_t second;
-};
-
-struct GpsState {
-  bool sawAnySentence = false;
-  uint8_t satsUsed = 0;
-  uint8_t satsInView = 0;
-
-  bool hasValidUtc = false;
-  uint16_t utcYear = 0;
-  uint8_t utcMonth = 0;
-  uint8_t utcDay = 0;
-  uint8_t utcHour = 0;
-  uint8_t utcMinute = 0;
-  uint8_t utcSecond = 0;
-};
-
-static GpsState g_gps;
-
-static void logf(const char* fmt, ...) {
-  char msg[220];
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(msg, sizeof(msg), fmt, args);
-  va_end(args);
-  Serial.printf("[%10lu][%06lu] %s\r\n", (unsigned long)millis(), (unsigned long)g_logSeq++, msg);
-}
-
-static void oledShowLines(const char* l1,
-                          const char* l2 = nullptr,
-                          const char* l3 = nullptr,
-                          const char* l4 = nullptr,
-                          const char* l5 = nullptr) {
-  g_oled.clearBuffer();
-  g_oled.setFont(u8g2_font_5x8_tf);
-  if (l1) g_oled.drawUTF8(0, 12, l1);
-  if (l2) g_oled.drawUTF8(0, 24, l2);
-  if (l3) g_oled.drawUTF8(0, 36, l3);
-  if (l4) g_oled.drawUTF8(0, 48, l4);
-  if (l5) g_oled.drawUTF8(0, 60, l5);
-  g_oled.sendBuffer();
-}
-
-static uint8_t fromBcd(uint8_t b) {
-  return ((b >> 4U) * 10U) + (b & 0x0FU);
-}
-
-static bool rtcRead(RtcDateTime& out, bool& lowVoltageFlag) {
-  Wire1.beginTransmission(RTC_I2C_ADDR);
-  Wire1.write(0x02);
-  if (Wire1.endTransmission(false) != 0) {
-    return false;
-  }
-
-  const uint8_t need = 7;
-  uint8_t got = Wire1.requestFrom((int)RTC_I2C_ADDR, (int)need);
-  if (got != need) {
-    return false;
-  }
-
-  uint8_t sec = Wire1.read();
-  uint8_t min = Wire1.read();
-  uint8_t hour = Wire1.read();
-  uint8_t day = Wire1.read();
-  (void)Wire1.read();
-  uint8_t month = Wire1.read();
-  uint8_t year = Wire1.read();
-
-  lowVoltageFlag = (sec & 0x80U) != 0;
-  out.second = fromBcd(sec & 0x7FU);
-  out.minute = fromBcd(min & 0x7FU);
-  out.hour = fromBcd(hour & 0x3FU);
-  out.day = fromBcd(day & 0x3FU);
-  out.month = fromBcd(month & 0x1FU);
-  uint8_t yy = fromBcd(year);
-  bool century = (month & 0x80U) != 0;
-  out.year = century ? (1900U + yy) : (2000U + yy);
-  return true;
-}
-
-static String formatRtcNow() {
-  RtcDateTime now{};
-  bool lowV = false;
-  if (!rtcRead(now, lowV)) {
-    return "RTC read failed";
-  }
-
-  char buf[48];
-  snprintf(buf,
-           sizeof(buf),
-           "RTC %04u-%02u-%02u %02u:%02u:%02u%s",
-           (unsigned)now.year,
-           (unsigned)now.month,
-           (unsigned)now.day,
-           (unsigned)now.hour,
-           (unsigned)now.minute,
-           (unsigned)now.second,
-           lowV ? " !LOWV" : "");
-  return String(buf);
-}
-
-static bool parseUInt2(const char* s, uint8_t& out) {
-  if (!s || !isdigit((unsigned char)s[0]) || !isdigit((unsigned char)s[1])) {
-    return false;
-  }
-  out = (uint8_t)((s[0] - '0') * 10 + (s[1] - '0'));
-  return true;
-}
-
-static void parseGga(char* fields[], int count) {
-  if (count <= 7) {
-    return;
-  }
-  int sats = atoi(fields[7]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsUsed = (uint8_t)sats;
-  }
-}
-
-static void parseGsv(char* fields[], int count) {
-  if (count <= 3) {
-    return;
-  }
-  int sats = atoi(fields[3]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsInView = (uint8_t)sats;
-  }
-}
-
-static void parseRmc(char* fields[], int count) {
-  if (count <= 9) {
-    return;
-  }
-
-  const char* utc = fields[1];
-  const char* status = fields[2];
-  const char* date = fields[9];
-
-  if (!status || status[0] != 'A') {
-    return;
-  }
-
-  if (!utc || strlen(utc) < 6 || !date || strlen(date) < 6) {
-    return;
-  }
-
-  uint8_t hh = 0, mm = 0, ss = 0;
-  uint8_t dd = 0, mo = 0, yy = 0;
-  if (!parseUInt2(utc + 0, hh) || !parseUInt2(utc + 2, mm) || !parseUInt2(utc + 4, ss)) {
-    return;
-  }
-  if (!parseUInt2(date + 0, dd) || !parseUInt2(date + 2, mo) || !parseUInt2(date + 4, yy)) {
-    return;
-  }
-
-  g_gps.utcHour = hh;
-  g_gps.utcMinute = mm;
-  g_gps.utcSecond = ss;
-  g_gps.utcDay = dd;
-  g_gps.utcMonth = mo;
-  g_gps.utcYear = (uint16_t)(2000U + yy);
-  g_gps.hasValidUtc = true;
-}
-
-static void processNmeaLine(char* line) {
-  if (!line || line[0] != '$') {
-    return;
-  }
-
-  g_gps.sawAnySentence = true;
-
-  char* star = strchr(line, '*');
-  if (star) {
-    *star = '\0';
-  }
-
-  char* fields[24] = {0};
-  int count = 0;
-  char* saveptr = nullptr;
-  char* tok = strtok_r(line, ",", &saveptr);
-  while (tok && count < 24) {
-    fields[count++] = tok;
-    tok = strtok_r(nullptr, ",", &saveptr);
-  }
-
-  if (count <= 0 || !fields[0]) {
-    return;
-  }
-
-  const char* header = fields[0];
-  size_t n = strlen(header);
-  if (n < 6) {
-    return;
-  }
-
-  const char* type = header + (n - 3);
-  if (strcmp(type, "GGA") == 0) {
-    parseGga(fields, count);
-  } else if (strcmp(type, "GSV") == 0) {
-    parseGsv(fields, count);
-  } else if (strcmp(type, "RMC") == 0) {
-    parseRmc(fields, count);
-  }
-}
-
-static void pollGpsSerial() {
-  while (g_gpsSerial.available() > 0) {
-    char c = (char)g_gpsSerial.read();
-    if (c == '\r') {
-      continue;
-    }
-    if (c == '\n') {
-      if (g_gpsLineLen > 0) {
-        g_gpsLine[g_gpsLineLen] = '\0';
-        processNmeaLine(g_gpsLine);
-        g_gpsLineLen = 0;
-      }
-      continue;
-    }
-
-    if (g_gpsLineLen + 1 < sizeof(g_gpsLine)) {
-      g_gpsLine[g_gpsLineLen++] = c;
-    } else {
-      g_gpsLineLen = 0;
-    }
-  }
-}
-
-static void startGpsUart(uint32_t baud) {
-  g_gpsSerial.end();
-  delay(20);
-  g_gpsSerial.setRxBufferSize(1024);
-  g_gpsSerial.begin(baud, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
-  g_gpsBaud = baud;
-}
-
-static bool collectGpsTraffic(uint32_t windowMs) {
-  uint32_t start = millis();
-  size_t bytesSeen = 0;
-  while ((uint32_t)(millis() - start) < windowMs) {
-    while (g_gpsSerial.available() > 0) {
-      (void)g_gpsSerial.read();
-      bytesSeen++;
-    }
-    pollGpsSerial();
-    delay(2);
-  }
-  return bytesSeen > 0 || g_gps.sawAnySentence;
-}
-
-static bool probeGpsAtBaud(uint32_t baud) {
-  startGpsUart(baud);
-  logf("Probing GPS at %lu baud...", (unsigned long)baud);
-  if (collectGpsTraffic(700)) {
-    return true;
-  }
-
-  // Try common query/wake commands used by MTK/L76K and related chipsets.
-  g_gpsSerial.write("$PCAS06,0*1B\r\n");     // Request module SW text
-  g_gpsSerial.write("$PMTK605*31\r\n");      // MTK firmware query
-  g_gpsSerial.write("$PQTMVERNO*58\r\n");    // Quectel LC86 query
-  g_gpsSerial.write("$PMTK353,1,1,1,1,1*2A\r\n");
-  g_gpsSerial.write("$PMTK314,0,1,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n");
-
-  return collectGpsTraffic(1200);
-}
-
-static void initialGpsProbe() {
-  const uint32_t bauds[] = {GPS_BAUD, 115200, 38400, 57600, 19200};
-  for (size_t i = 0; i < sizeof(bauds) / sizeof(bauds[0]); ++i) {
-    if (probeGpsAtBaud(bauds[i])) {
-      logf("GPS traffic detected at %lu baud", (unsigned long)g_gpsBaud);
-      return;
-    }
-  }
-  logf("No GPS traffic detected during startup probe");
-}
-
-static uint8_t bestSatelliteCount() {
-  return (g_gps.satsUsed > g_gps.satsInView) ? g_gps.satsUsed : g_gps.satsInView;
-}
-
-static void showTryingMessage() {
-  String rtc = formatRtcNow();
-  oledShowLines("Trying to locate",
-                "satellites",
-                g_gps.sawAnySentence ? "NMEA seen: yes" : "NMEA seen: no",
-                rtc.c_str());
-  logf("Trying to locate satellites. %s", rtc.c_str());
-}
-
-static void showStatusMessage() {
-  uint8_t sats = bestSatelliteCount();
-
-  if (g_gps.hasValidUtc) {
-    char line2[40];
-    char line3[28];
-    snprintf(line2,
-             sizeof(line2),
-             "GPS UTC %04u-%02u-%02u",
-             (unsigned)g_gps.utcYear,
-             (unsigned)g_gps.utcMonth,
-             (unsigned)g_gps.utcDay);
-    snprintf(line3,
-             sizeof(line3),
-             "%02u:%02u:%02u  sats:%u",
-             (unsigned)g_gps.utcHour,
-             (unsigned)g_gps.utcMinute,
-             (unsigned)g_gps.utcSecond,
-             (unsigned)sats);
-    oledShowLines("GPS lock acquired",
-                  line2,
-                  line3,
-                  g_gps.sawAnySentence ? "NMEA seen: yes" : "NMEA seen: no");
-    logf("GPS lock acquired. %s  sats=%u", line3, (unsigned)sats);
-    return;
-  }
-
-  String rtc = formatRtcNow();
-  oledShowLines("Take me outside",
-                "No GPS time/sats yet",
-                g_gps.sawAnySentence ? "NMEA seen: yes" : "NMEA seen: no",
-                rtc.c_str());
-  logf("Take me outside. sats=%u, has_utc=%s, nmea_seen=%s. %s",
-       (unsigned)sats,
-       g_gps.hasValidUtc ? "yes" : "no",
-       g_gps.sawAnySentence ? "yes" : "no",
-       rtc.c_str());
-}
-
-void setup() {
-  Serial.begin(115200);
-  delay(kSerialDelayMs);
-
-  Serial.println("\r\n==================================================");
-  Serial.println("Exercise 10: Simple GPS (No SD)");
-  Serial.println("==================================================");
-
-  if (!tbeam_supreme::initPmuForPeripherals(g_pmu, &Serial)) {
-    logf("PMU init failed");
-  }
-
-  Wire.begin(OLED_SDA, OLED_SCL);
-  g_oled.setI2CAddress(OLED_ADDR << 1);
-  g_oled.begin();
-  oledShowLines("Simple GPS", "Booting...");
-
-#ifdef GPS_1PPS_PIN
-  pinMode(GPS_1PPS_PIN, INPUT);
-#endif
-
-#ifdef GPS_WAKEUP_PIN
-  // Keep wake pin in a neutral state similar to Meshtastic behavior.
-  pinMode(GPS_WAKEUP_PIN, INPUT);
-#endif
-
-  startGpsUart(GPS_BAUD);
-  logf("GPS UART started: RX=%d TX=%d baud=%lu", GPS_RX_PIN, GPS_TX_PIN, (unsigned long)g_gpsBaud);
-  initialGpsProbe();
-
-  showTryingMessage();
-  g_lastReportMs = millis();
-}
-
-void loop() {
-  pollGpsSerial();
-
-  uint32_t now = millis();
-  if ((uint32_t)(now - g_lastReportMs) >= kReportIntervalMs) {
-    g_lastReportMs = now;
-
-    showTryingMessage();
-    uint32_t start = millis();
-    while ((uint32_t)(millis() - start) < 2000) {
-      pollGpsSerial();
-      delay(5);
-    }
-
-    showStatusMessage();
-  }
-}
diff --git a/exercises/11_Set_RTC2GPS/README.md b/exercises/11_Set_RTC2GPS/README.md
deleted file mode 100644
index 462c2d2..0000000
--- a/exercises/11_Set_RTC2GPS/README.md
+++ /dev/null
@@ -1,33 +0,0 @@
-## Exercise 11: Set RTC to GPS (1PPS Discipline)
-
-This exercise extends Exercise 9 behavior (GPS + SD + OLED) and disciplines the onboard RTC from GPS UTC using the GPS `1PPS` (pulse-per-second) timing signal.
-
-Implemented behavior:
-
-1. Boots PMU, OLED, SD watcher, and GPS UART using the same T-Beam Supreme pin mapping from prior exercises.
-2. Parses NMEA (`RMC`, `GGA`, `GSV`) to track UTC validity and satellite counts.
-3. Every 1 minute, attempts to set RTC from GPS:
-   - Uses latest valid GPS UTC.
-   - Waits for next `1PPS` rising edge.
-   - Sets RTC to GPS time aligned to that edge (UTC + 1 second).
-4. Appends event records to SD file:
-   - Path: `/gps/discipline_rtc.log`
-   - Append-only writes (`FILE_APPEND`)
-   - Format:
-     - `YYYYMMDD_HH24MISS_z\t set RTC to GPS using 1PPS pulse-per-second discipline\trtc-gps drift=+/-Ns`
-5. OLED success message shows RTC disciplined confirmation and timestamp.
-6. If GPS time cannot be determined (or 1PPS edge is not seen in timeout), OLED shows failure status and the loop delays 30 seconds before retry.
-
-## Build
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a
-```
-
-## Upload
-
-```bash
-source /home/jlpoole/rnsenv/bin/activate
-pio run -e node_a -t upload --upload-port /dev/ttyACM0
-```
diff --git a/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.cpp b/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.cpp
deleted file mode 100644
index 1e8791c..0000000
--- a/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.cpp
+++ /dev/null
@@ -1,360 +0,0 @@
-#include "StartupSdManager.h"
-
-#include <stdarg.h>
-#include "driver/gpio.h"
-
-StartupSdManager::StartupSdManager(Print& serial) : serial_(serial) {}
-
-bool StartupSdManager::begin(const SdWatcherConfig& cfg, SdStatusCallback callback) {
-  cfg_ = cfg;
-  callback_ = callback;
-
-  forceSpiDeselected();
-  dumpSdPins("very-early");
-
-  if (!initPmuForSdPower()) {
-    return false;
-  }
-
-  cycleSdRail();
-  delay(cfg_.startupWarmupMs);
-
-  bool warmMounted = false;
-  for (uint8_t i = 0; i < 3; ++i) {
-    if (mountPreferred(false)) {
-      warmMounted = true;
-      break;
-    }
-    delay(200);
-  }
-
-  // Some cards need a longer power/settle window after cold boot.
-  // Before declaring ABSENT, retry with extended settle and a full scan.
-  if (!warmMounted) {
-    logf("Watcher: startup preferred mount failed, retrying with extended settle");
-    cycleSdRail(400, 1200);
-    delay(cfg_.startupWarmupMs + 1500);
-    warmMounted = mountCardFullScan();
-  }
-
-  if (warmMounted) {
-    setStateMounted();
-  } else {
-    setStateAbsent();
-  }
-  return true;
-}
-
-void StartupSdManager::update() {
-  const uint32_t now = millis();
-  const uint32_t pollInterval =
-      (watchState_ == SdWatchState::MOUNTED) ? cfg_.pollIntervalMountedMs : cfg_.pollIntervalAbsentMs;
-
-  if ((uint32_t)(now - lastPollMs_) < pollInterval) {
-    return;
-  }
-  lastPollMs_ = now;
-
-  if (watchState_ == SdWatchState::MOUNTED) {
-    if (verifyMountedCard()) {
-      presentVotes_ = 0;
-      absentVotes_ = 0;
-      return;
-    }
-
-    if (mountPreferred(false) && verifyMountedCard()) {
-      presentVotes_ = 0;
-      absentVotes_ = 0;
-      return;
-    }
-
-    absentVotes_++;
-    presentVotes_ = 0;
-    if (absentVotes_ >= cfg_.votesToAbsent) {
-      setStateAbsent();
-      absentVotes_ = 0;
-    }
-    return;
-  }
-
-  bool mounted = mountPreferred(false);
-  if (!mounted && (uint32_t)(now - lastFullScanMs_) >= cfg_.fullScanIntervalMs) {
-    lastFullScanMs_ = now;
-    if (cfg_.recoveryRailCycleOnFullScan) {
-      logf("Watcher: recovery rail cycle before full scan");
-      cycleSdRail(cfg_.recoveryRailOffMs, cfg_.recoveryRailOnSettleMs);
-      delay(150);
-    }
-    logf("Watcher: preferred probe failed, running full scan");
-    mounted = mountCardFullScan();
-  }
-
-  if (mounted) {
-    presentVotes_++;
-    absentVotes_ = 0;
-    if (presentVotes_ >= cfg_.votesToPresent) {
-      setStateMounted();
-      presentVotes_ = 0;
-    }
-  } else {
-    absentVotes_++;
-    presentVotes_ = 0;
-    if (absentVotes_ >= cfg_.votesToAbsent) {
-      setStateAbsent();
-      absentVotes_ = 0;
-    }
-  }
-}
-
-bool StartupSdManager::consumeMountedEvent() {
-  bool out = mountedEventPending_;
-  mountedEventPending_ = false;
-  return out;
-}
-
-bool StartupSdManager::consumeRemovedEvent() {
-  bool out = removedEventPending_;
-  removedEventPending_ = false;
-  return out;
-}
-
-void StartupSdManager::logf(const char* fmt, ...) {
-  char msg[196];
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(msg, sizeof(msg), fmt, args);
-  va_end(args);
-  serial_.printf("[%10lu][%06lu] %s\r\n",
-                 (unsigned long)millis(),
-                 (unsigned long)logSeq_++,
-                 msg);
-}
-
-void StartupSdManager::notify(SdEvent event, const char* message) {
-  if (callback_ != nullptr) {
-    callback_(event, message);
-  }
-}
-
-void StartupSdManager::forceSpiDeselected() {
-  pinMode(tbeam_supreme::sdCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::sdCs(), HIGH);
-  pinMode(tbeam_supreme::imuCs(), OUTPUT);
-  digitalWrite(tbeam_supreme::imuCs(), HIGH);
-}
-
-void StartupSdManager::dumpSdPins(const char* tag) {
-  if (!cfg_.enablePinDumps) {
-    (void)tag;
-    return;
-  }
-
-  const gpio_num_t cs = (gpio_num_t)tbeam_supreme::sdCs();
-  const gpio_num_t sck = (gpio_num_t)tbeam_supreme::sdSck();
-  const gpio_num_t miso = (gpio_num_t)tbeam_supreme::sdMiso();
-  const gpio_num_t mosi = (gpio_num_t)tbeam_supreme::sdMosi();
-  logf("PINS(%s): CS=%d SCK=%d MISO=%d MOSI=%d",
-       tag, gpio_get_level(cs), gpio_get_level(sck), gpio_get_level(miso), gpio_get_level(mosi));
-}
-
-bool StartupSdManager::initPmuForSdPower() {
-  if (!tbeam_supreme::initPmuForPeripherals(pmu_, &serial_)) {
-    logf("ERROR: PMU init failed");
-    return false;
-  }
-  return true;
-}
-
-void StartupSdManager::cycleSdRail(uint32_t offMs, uint32_t onSettleMs) {
-  if (!cfg_.enableSdRailCycle) {
-    return;
-  }
-  if (!pmu_) {
-    logf("SD rail cycle skipped: pmu=null");
-    return;
-  }
-
-  forceSpiDeselected();
-  pmu_->disablePowerOutput(XPOWERS_BLDO1);
-  delay(offMs);
-  pmu_->setPowerChannelVoltage(XPOWERS_BLDO1, 3300);
-  pmu_->enablePowerOutput(XPOWERS_BLDO1);
-  delay(onSettleMs);
-}
-
-bool StartupSdManager::tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz, bool verbose) {
-  SD.end();
-  bus.end();
-  delay(10);
-  forceSpiDeselected();
-
-  bus.begin(tbeam_supreme::sdSck(), tbeam_supreme::sdMiso(), tbeam_supreme::sdMosi(), tbeam_supreme::sdCs());
-  digitalWrite(tbeam_supreme::sdCs(), HIGH);
-  delay(2);
-  for (int i = 0; i < 10; i++) {
-    bus.transfer(0xFF);
-  }
-  delay(2);
-
-  if (verbose) {
-    logf("SD: trying bus=%s freq=%lu Hz", busName, (unsigned long)hz);
-  }
-
-  if (!SD.begin(tbeam_supreme::sdCs(), bus, hz)) {
-    if (verbose) {
-      logf("SD: mount failed (possible non-FAT format, power, or bus issue)");
-    }
-    return false;
-  }
-
-  if (SD.cardType() == CARD_NONE) {
-    SD.end();
-    return false;
-  }
-
-  sdSpi_ = &bus;
-  sdBusName_ = busName;
-  sdFreq_ = hz;
-  return true;
-}
-
-bool StartupSdManager::mountPreferred(bool verbose) {
-  return tryMountWithBus(sdSpiH_, "HSPI", 400000, verbose);
-}
-
-bool StartupSdManager::mountCardFullScan() {
-  const uint32_t freqs[] = {400000, 1000000, 4000000, 10000000};
-
-  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
-    if (tryMountWithBus(sdSpiH_, "HSPI", freqs[i], true)) {
-      logf("SD: card detected and mounted");
-      return true;
-    }
-  }
-  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
-    if (tryMountWithBus(sdSpiF_, "FSPI", freqs[i], true)) {
-      logf("SD: card detected and mounted");
-      return true;
-    }
-  }
-
-  logf("SD: begin() failed on all bus/frequency attempts");
-  return false;
-}
-
-bool StartupSdManager::verifyMountedCard() {
-  File root = SD.open("/", FILE_READ);
-  if (!root) {
-    return false;
-  }
-  root.close();
-  return true;
-}
-
-const char* StartupSdManager::cardTypeToString(uint8_t type) {
-  switch (type) {
-    case CARD_MMC:
-      return "MMC";
-    case CARD_SD:
-      return "SDSC";
-    case CARD_SDHC:
-      return "SDHC/SDXC";
-    default:
-      return "UNKNOWN";
-  }
-}
-
-void StartupSdManager::printCardInfo() {
-  uint8_t cardType = SD.cardType();
-  uint64_t cardSizeMB = SD.cardSize() / (1024ULL * 1024ULL);
-  uint64_t totalMB = SD.totalBytes() / (1024ULL * 1024ULL);
-  uint64_t usedMB = SD.usedBytes() / (1024ULL * 1024ULL);
-
-  logf("SD type: %s", cardTypeToString(cardType));
-  logf("SD size: %llu MB", cardSizeMB);
-  logf("FS total: %llu MB", totalMB);
-  logf("FS used : %llu MB", usedMB);
-  logf("SPI bus: %s @ %lu Hz", sdBusName_, (unsigned long)sdFreq_);
-}
-
-bool StartupSdManager::ensureDirRecursive(const char* path) {
-  String full(path);
-  if (!full.startsWith("/")) {
-    full = "/" + full;
-  }
-
-  int start = 1;
-  while (start > 0 && start < (int)full.length()) {
-    int slash = full.indexOf('/', start);
-    String partial = (slash < 0) ? full : full.substring(0, slash);
-    if (!SD.exists(partial.c_str()) && !SD.mkdir(partial.c_str())) {
-      logf("ERROR: mkdir failed for %s", partial.c_str());
-      return false;
-    }
-    if (slash < 0) {
-      break;
-    }
-    start = slash + 1;
-  }
-
-  return true;
-}
-
-bool StartupSdManager::rewriteFile(const char* path, const char* payload) {
-  if (SD.exists(path) && !SD.remove(path)) {
-    logf("ERROR: failed to erase %s", path);
-    return false;
-  }
-
-  File f = SD.open(path, FILE_WRITE);
-  if (!f) {
-    logf("ERROR: failed to create %s", path);
-    return false;
-  }
-
-  size_t wrote = f.println(payload);
-  f.close();
-  if (wrote == 0) {
-    logf("ERROR: write failed for %s", path);
-    return false;
-  }
-  return true;
-}
-
-void StartupSdManager::permissionsDemo(const char* path) {
-  logf("Permissions demo: FAT has no Unix chmod/chown, use open mode only.");
-  File r = SD.open(path, FILE_READ);
-  if (!r) {
-    logf("Could not open %s as FILE_READ", path);
-    return;
-  }
-  size_t writeInReadMode = r.print("attempt write while opened read-only");
-  if (writeInReadMode == 0) {
-    logf("As expected, FILE_READ write was blocked.");
-  } else {
-    logf("NOTE: FILE_READ write returned %u (unexpected)", (unsigned)writeInReadMode);
-  }
-  r.close();
-}
-
-void StartupSdManager::setStateMounted() {
-  if (watchState_ != SdWatchState::MOUNTED) {
-    logf("EVENT: card inserted/mounted");
-    mountedEventPending_ = true;
-    notify(SdEvent::CARD_MOUNTED, "SD card mounted");
-  }
-  watchState_ = SdWatchState::MOUNTED;
-}
-
-void StartupSdManager::setStateAbsent() {
-  if (watchState_ == SdWatchState::MOUNTED) {
-    logf("EVENT: card removed/unavailable");
-    removedEventPending_ = true;
-    notify(SdEvent::CARD_REMOVED, "SD card removed");
-  } else if (watchState_ != SdWatchState::ABSENT) {
-    logf("EVENT: no card detected");
-    notify(SdEvent::NO_CARD, "Missing SD card or invalid FAT16/FAT32 format");
-  }
-  SD.end();
-  watchState_ = SdWatchState::ABSENT;
-}
diff --git a/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.h b/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.h
deleted file mode 100644
index be9ef27..0000000
--- a/exercises/11_Set_RTC2GPS/lib/startup_sd/StartupSdManager.h
+++ /dev/null
@@ -1,90 +0,0 @@
-#pragma once
-
-#include <Arduino.h>
-#include <SD.h>
-#include <SPI.h>
-#include <Wire.h>
-#include "tbeam_supreme_adapter.h"
-
-enum class SdWatchState : uint8_t {
-  UNKNOWN = 0,
-  ABSENT,
-  MOUNTED
-};
-
-enum class SdEvent : uint8_t {
-  NO_CARD,
-  CARD_MOUNTED,
-  CARD_REMOVED
-};
-
-using SdStatusCallback = void (*)(SdEvent event, const char* message);
-
-struct SdWatcherConfig {
-  bool enableSdRailCycle = true;
-  bool enablePinDumps = true;
-  bool recoveryRailCycleOnFullScan = true;
-  uint32_t recoveryRailOffMs = 250;
-  uint32_t recoveryRailOnSettleMs = 700;
-  uint32_t startupWarmupMs = 1500;
-  uint32_t pollIntervalAbsentMs = 1000;
-  uint32_t pollIntervalMountedMs = 2000;
-  uint32_t fullScanIntervalMs = 10000;
-  uint8_t votesToPresent = 2;
-  uint8_t votesToAbsent = 5;
-};
-
-class StartupSdManager {
- public:
-  explicit StartupSdManager(Print& serial = Serial);
-
-  bool begin(const SdWatcherConfig& cfg, SdStatusCallback callback = nullptr);
-  void update();
-
-  bool isMounted() const { return watchState_ == SdWatchState::MOUNTED; }
-  SdWatchState state() const { return watchState_; }
-
-  bool consumeMountedEvent();
-  bool consumeRemovedEvent();
-
-  void printCardInfo();
-  bool ensureDirRecursive(const char* path);
-  bool rewriteFile(const char* path, const char* payload);
-  void permissionsDemo(const char* path);
-
- private:
-  void logf(const char* fmt, ...);
-  void notify(SdEvent event, const char* message);
-  void forceSpiDeselected();
-  void dumpSdPins(const char* tag);
-  bool initPmuForSdPower();
-  void cycleSdRail(uint32_t offMs = 250, uint32_t onSettleMs = 600);
-  bool tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz, bool verbose);
-  bool mountPreferred(bool verbose);
-  bool mountCardFullScan();
-  bool verifyMountedCard();
-  const char* cardTypeToString(uint8_t type);
-  void setStateMounted();
-  void setStateAbsent();
-
-  Print& serial_;
-  SdWatcherConfig cfg_{};
-  SdStatusCallback callback_ = nullptr;
-
-  SPIClass sdSpiH_{HSPI};
-  SPIClass sdSpiF_{FSPI};
-  SPIClass* sdSpi_ = nullptr;
-  const char* sdBusName_ = "none";
-  uint32_t sdFreq_ = 0;
-  XPowersLibInterface* pmu_ = nullptr;
-
-  SdWatchState watchState_ = SdWatchState::UNKNOWN;
-  uint8_t presentVotes_ = 0;
-  uint8_t absentVotes_ = 0;
-  uint32_t lastPollMs_ = 0;
-  uint32_t lastFullScanMs_ = 0;
-  uint32_t logSeq_ = 0;
-
-  bool mountedEventPending_ = false;
-  bool removedEventPending_ = false;
-};
diff --git a/exercises/11_Set_RTC2GPS/lib/startup_sd/library.json b/exercises/11_Set_RTC2GPS/lib/startup_sd/library.json
deleted file mode 100644
index 4978fdd..0000000
--- a/exercises/11_Set_RTC2GPS/lib/startup_sd/library.json
+++ /dev/null
@@ -1,12 +0,0 @@
-{
-  "name": "startup_sd",
-  "version": "0.1.0",
-  "dependencies": [
-    {
-      "name": "XPowersLib"
-    },
-    {
-      "name": "Wire"
-    }
-  ]
-}
diff --git a/exercises/11_Set_RTC2GPS/platformio.ini b/exercises/11_Set_RTC2GPS/platformio.ini
deleted file mode 100644
index a91b0bc..0000000
--- a/exercises/11_Set_RTC2GPS/platformio.ini
+++ /dev/null
@@ -1,42 +0,0 @@
-; 20260213 ChatGPT
-; $Id$
-; $HeadURL$
-
-[platformio]
-default_envs = node_a
-
-[env]
-platform = espressif32
-framework = arduino
-board = esp32-s3-devkitc-1
-monitor_speed = 115200
-extra_scripts = pre:scripts/set_build_epoch.py
-lib_deps =
-  lewisxhe/XPowersLib@0.3.3
-  Wire
-  olikraus/U8g2@^2.36.4
-
-; SD pins based on T-Beam S3 core pin mapping
-build_flags =
-  -I ../../shared/boards
-  -I ../../external/microReticulum_Firmware
-  -D BOARD_MODEL=BOARD_TBEAM_S_V1
-  -D OLED_SDA=17
-  -D OLED_SCL=18
-  -D OLED_ADDR=0x3C
-  -D GPS_RX_PIN=9
-  -D GPS_TX_PIN=8
-  -D GPS_WAKEUP_PIN=7
-  -D GPS_1PPS_PIN=6
-  -D ARDUINO_USB_MODE=1
-  -D ARDUINO_USB_CDC_ON_BOOT=1
-
-[env:node_a]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"A\"
-
-[env:node_b]
-build_flags =
-  ${env.build_flags}
-  -D NODE_LABEL=\"B\"
diff --git a/exercises/11_Set_RTC2GPS/scripts/set_build_epoch.py b/exercises/11_Set_RTC2GPS/scripts/set_build_epoch.py
deleted file mode 100644
index 3011129..0000000
--- a/exercises/11_Set_RTC2GPS/scripts/set_build_epoch.py
+++ /dev/null
@@ -1,12 +0,0 @@
-import time
-Import("env")
-
-epoch = int(time.time())
-utc_tag = time.strftime("%Y%m%d_%H%M%S_z", time.gmtime(epoch))
-
-env.Append(
-    CPPDEFINES=[
-        ("FW_BUILD_EPOCH", str(epoch)),
-        ("FW_BUILD_UTC", '\\"%s\\"' % utc_tag),
-    ]
-)
diff --git a/exercises/11_Set_RTC2GPS/src/main.cpp b/exercises/11_Set_RTC2GPS/src/main.cpp
deleted file mode 100644
index 9e54ea7..0000000
--- a/exercises/11_Set_RTC2GPS/src/main.cpp
+++ /dev/null
@@ -1,786 +0,0 @@
-// 20260217 ChatGPT
-// $Id$
-// $HeadURL$
-
-#include <Arduino.h>
-#include <Wire.h>
-#include <SD.h>
-#include <U8g2lib.h>
-
-#include "StartupSdManager.h"
-#include "tbeam_supreme_adapter.h"
-
-#ifndef OLED_SDA
-#define OLED_SDA 17
-#endif
-
-#ifndef OLED_SCL
-#define OLED_SCL 18
-#endif
-
-#ifndef OLED_ADDR
-#define OLED_ADDR 0x3C
-#endif
-
-#ifndef RTC_I2C_ADDR
-#define RTC_I2C_ADDR 0x51
-#endif
-
-#ifndef GPS_BAUD
-#define GPS_BAUD 9600
-#endif
-
-#ifndef FILE_APPEND
-#define FILE_APPEND FILE_WRITE
-#endif
-
-#ifndef FW_BUILD_EPOCH
-#define FW_BUILD_EPOCH 0
-#endif
-
-#ifndef FW_BUILD_UTC
-#define FW_BUILD_UTC "unknown"
-#endif
-
-static const uint32_t kSerialDelayMs = 5000;
-static const uint32_t kLoopMsDiscipline = 60000;
-static const uint32_t kNoTimeDelayMs = 30000;
-static const uint32_t kGpsStartupProbeMs = 20000;
-static const uint32_t kPpsWaitTimeoutMs = 1500;
-
-static XPowersLibInterface* g_pmu = nullptr;
-static StartupSdManager g_sd(Serial);
-static U8G2_SH1106_128X64_NONAME_F_HW_I2C g_oled(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
-static HardwareSerial g_gpsSerial(1);
-
-static uint32_t g_logSeq = 0;
-static uint32_t g_nextDisciplineMs = 0;
-static bool g_gpsPathReady = false;
-
-static char g_gpsLine[128];
-static size_t g_gpsLineLen = 0;
-
-static volatile uint32_t g_ppsEdgeCount = 0;
-
-struct DateTime {
-  uint16_t year;
-  uint8_t month;
-  uint8_t day;
-  uint8_t hour;
-  uint8_t minute;
-  uint8_t second;
-};
-
-struct GpsState {
-  bool sawAnySentence = false;
-  bool hasValidUtc = false;
-  bool hasValidPosition = false;
-  bool hasValidAltitude = false;
-  uint8_t satsUsed = 0;
-  uint8_t satsInView = 0;
-  float hdop = -1.0f;
-  float altitudeM = 0.0f;
-  double latitudeDeg = 0.0;
-  double longitudeDeg = 0.0;
-  DateTime utc{};
-  uint32_t lastUtcMs = 0;
-};
-
-static GpsState g_gps;
-
-static void logf(const char* fmt, ...) {
-  char msg[240];
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(msg, sizeof(msg), fmt, args);
-  va_end(args);
-  Serial.printf("[%10lu][%06lu] %s\r\n", (unsigned long)millis(), (unsigned long)g_logSeq++, msg);
-}
-
-static void oledShowLines(const char* l1,
-                          const char* l2 = nullptr,
-                          const char* l3 = nullptr,
-                          const char* l4 = nullptr,
-                          const char* l5 = nullptr) {
-  g_oled.clearBuffer();
-  g_oled.setFont(u8g2_font_5x8_tf);
-  if (l1) g_oled.drawUTF8(0, 12, l1);
-  if (l2) g_oled.drawUTF8(0, 24, l2);
-  if (l3) g_oled.drawUTF8(0, 36, l3);
-  if (l4) g_oled.drawUTF8(0, 48, l4);
-  if (l5) g_oled.drawUTF8(0, 60, l5);
-  g_oled.sendBuffer();
-}
-
-static uint8_t toBcd(uint8_t v) {
-  return (uint8_t)(((v / 10U) << 4U) | (v % 10U));
-}
-
-static uint8_t fromBcd(uint8_t b) {
-  return (uint8_t)(((b >> 4U) * 10U) + (b & 0x0FU));
-}
-
-static bool rtcRead(DateTime& out, bool& lowVoltageFlag) {
-  Wire1.beginTransmission(RTC_I2C_ADDR);
-  Wire1.write(0x02);
-  if (Wire1.endTransmission(false) != 0) {
-    return false;
-  }
-
-  const uint8_t need = 7;
-  uint8_t got = Wire1.requestFrom((int)RTC_I2C_ADDR, (int)need);
-  if (got != need) {
-    return false;
-  }
-
-  uint8_t sec = Wire1.read();
-  uint8_t min = Wire1.read();
-  uint8_t hour = Wire1.read();
-  uint8_t day = Wire1.read();
-  (void)Wire1.read();
-  uint8_t month = Wire1.read();
-  uint8_t year = Wire1.read();
-
-  lowVoltageFlag = (sec & 0x80U) != 0;
-  out.second = fromBcd(sec & 0x7FU);
-  out.minute = fromBcd(min & 0x7FU);
-  out.hour = fromBcd(hour & 0x3FU);
-  out.day = fromBcd(day & 0x3FU);
-  out.month = fromBcd(month & 0x1FU);
-  uint8_t yy = fromBcd(year);
-  bool century = (month & 0x80U) != 0;
-  out.year = century ? (1900U + yy) : (2000U + yy);
-  return true;
-}
-
-static bool rtcWrite(const DateTime& dt) {
-  Wire1.beginTransmission(RTC_I2C_ADDR);
-  Wire1.write(0x02);
-  Wire1.write(toBcd(dt.second & 0x7FU));
-  Wire1.write(toBcd(dt.minute));
-  Wire1.write(toBcd(dt.hour));
-  Wire1.write(toBcd(dt.day));
-  Wire1.write(0x00);
-
-  uint8_t monthReg = toBcd(dt.month);
-  if (dt.year < 2000U) {
-    monthReg |= 0x80U;
-  }
-  Wire1.write(monthReg);
-  Wire1.write(toBcd((uint8_t)(dt.year % 100U)));
-
-  return Wire1.endTransmission() == 0;
-}
-
-static bool isLeapYear(uint16_t y) {
-  return ((y % 4U) == 0U && (y % 100U) != 0U) || ((y % 400U) == 0U);
-}
-
-static uint8_t daysInMonth(uint16_t year, uint8_t month) {
-  static const uint8_t kDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
-  if (month == 2) {
-    return (uint8_t)(isLeapYear(year) ? 29 : 28);
-  }
-  if (month >= 1 && month <= 12) {
-    return kDays[month - 1];
-  }
-  return 30;
-}
-
-static bool isValidDateTime(const DateTime& dt) {
-  if (dt.year < 2000U || dt.year > 2099U) return false;
-  if (dt.month < 1 || dt.month > 12) return false;
-  if (dt.day < 1 || dt.day > daysInMonth(dt.year, dt.month)) return false;
-  if (dt.hour > 23 || dt.minute > 59 || dt.second > 59) return false;
-  return true;
-}
-
-static int64_t daysFromCivil(int y, unsigned m, unsigned d) {
-  y -= (m <= 2);
-  const int era = (y >= 0 ? y : y - 399) / 400;
-  const unsigned yoe = (unsigned)(y - era * 400);
-  const unsigned doy = (153 * (m + (m > 2 ? (unsigned)-3 : 9)) + 2) / 5 + d - 1;
-  const unsigned doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;
-  return era * 146097 + (int)doe - 719468;
-}
-
-static int64_t toEpochSeconds(const DateTime& dt) {
-  int64_t days = daysFromCivil((int)dt.year, dt.month, dt.day);
-  return days * 86400LL + (int64_t)dt.hour * 3600LL + (int64_t)dt.minute * 60LL + (int64_t)dt.second;
-}
-
-static bool fromEpochSeconds(int64_t sec, DateTime& out) {
-  if (sec < 0) {
-    return false;
-  }
-
-  int64_t days = sec / 86400LL;
-  int64_t rem = sec % 86400LL;
-  if (rem < 0) {
-    rem += 86400LL;
-    days -= 1;
-  }
-
-  out.hour = (uint8_t)(rem / 3600LL);
-  rem %= 3600LL;
-  out.minute = (uint8_t)(rem / 60LL);
-  out.second = (uint8_t)(rem % 60LL);
-
-  days += 719468;
-  const int era = (days >= 0 ? days : days - 146096) / 146097;
-  const unsigned doe = (unsigned)(days - era * 146097);
-  const unsigned yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
-  int y = (int)yoe + era * 400;
-  const unsigned doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
-  const unsigned mp = (5 * doy + 2) / 153;
-  const unsigned d = doy - (153 * mp + 2) / 5 + 1;
-  const unsigned m = mp + (mp < 10 ? 3 : (unsigned)-9);
-  y += (m <= 2);
-
-  out.year = (uint16_t)y;
-  out.month = (uint8_t)m;
-  out.day = (uint8_t)d;
-  return isValidDateTime(out);
-}
-
-static void addOneSecond(DateTime& dt) {
-  int64_t t = toEpochSeconds(dt);
-  DateTime out{};
-  if (fromEpochSeconds(t + 1, out)) {
-    dt = out;
-  }
-}
-
-static void formatUtcCompact(const DateTime& dt, char* out, size_t outLen) {
-  snprintf(out,
-           outLen,
-           "%04u%02u%02u_%02u%02u%02u_z",
-           (unsigned)dt.year,
-           (unsigned)dt.month,
-           (unsigned)dt.day,
-           (unsigned)dt.hour,
-           (unsigned)dt.minute,
-           (unsigned)dt.second);
-}
-
-static void formatUtcHuman(const DateTime& dt, char* out, size_t outLen) {
-  snprintf(out,
-           outLen,
-           "%04u-%02u-%02u %02u:%02u:%02u UTC",
-           (unsigned)dt.year,
-           (unsigned)dt.month,
-           (unsigned)dt.day,
-           (unsigned)dt.hour,
-           (unsigned)dt.minute,
-           (unsigned)dt.second);
-}
-
-static bool parseUInt2(const char* s, uint8_t& out) {
-  if (!s || !isdigit((unsigned char)s[0]) || !isdigit((unsigned char)s[1])) {
-    return false;
-  }
-  out = (uint8_t)((s[0] - '0') * 10 + (s[1] - '0'));
-  return true;
-}
-
-static bool parseNmeaCoordToDecimal(const char* raw, const char* hemi, bool isLat, double& outDeg) {
-  if (!raw || !hemi || raw[0] == '\0' || hemi[0] == '\0') {
-    return false;
-  }
-
-  // NMEA uses ddmm.mmmm (lat) and dddmm.mmmm (lon), with leading zeros preserved.
-  // Parse from string slices so longitudes like 071xx.xxxx do not collapse to 7xx.xxxx.
-  int degDigits = isLat ? 2 : 3;
-  size_t n = strlen(raw);
-  if (n <= (size_t)degDigits + 2) {
-    return false;
-  }
-
-  for (int i = 0; i < degDigits; ++i) {
-    if (!isdigit((unsigned char)raw[i])) {
-      return false;
-    }
-  }
-
-  char degBuf[4] = {0};
-  memcpy(degBuf, raw, degDigits);
-  int deg = atoi(degBuf);
-
-  const char* minPtr = raw + degDigits;
-  double minutes = atof(minPtr);
-  if (minutes < 0.0 || minutes >= 60.0) {
-    return false;
-  }
-
-  double dec = (double)deg + (minutes / 60.0);
-  char h = (char)toupper((unsigned char)hemi[0]);
-  if (h == 'S' || h == 'W') {
-    dec = -dec;
-  } else if (h != 'N' && h != 'E') {
-    return false;
-  }
-
-  outDeg = dec;
-  return true;
-}
-
-static void parseGga(char* fields[], int count) {
-  if (count <= 7) {
-    return;
-  }
-  const char* latRaw = (count > 2) ? fields[2] : nullptr;
-  const char* latHem = (count > 3) ? fields[3] : nullptr;
-  const char* lonRaw = (count > 4) ? fields[4] : nullptr;
-  const char* lonHem = (count > 5) ? fields[5] : nullptr;
-  int sats = atoi(fields[7]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsUsed = (uint8_t)sats;
-  }
-  if (count > 8 && fields[8] && fields[8][0] != '\0') {
-    g_gps.hdop = (float)atof(fields[8]);
-  }
-  if (count > 9 && fields[9] && fields[9][0] != '\0') {
-    g_gps.altitudeM = (float)atof(fields[9]);
-    g_gps.hasValidAltitude = true;
-  }
-
-  // Position fallback from GGA so we still log coordinates if RMC position is missing.
-  double lat = 0.0;
-  double lon = 0.0;
-  if (parseNmeaCoordToDecimal(latRaw, latHem, true, lat) &&
-      parseNmeaCoordToDecimal(lonRaw, lonHem, false, lon)) {
-    g_gps.latitudeDeg = lat;
-    g_gps.longitudeDeg = lon;
-    g_gps.hasValidPosition = true;
-  }
-}
-
-static void parseGsv(char* fields[], int count) {
-  if (count <= 3) {
-    return;
-  }
-  int sats = atoi(fields[3]);
-  if (sats >= 0 && sats <= 255) {
-    g_gps.satsInView = (uint8_t)sats;
-  }
-}
-
-static void parseRmc(char* fields[], int count) {
-  if (count <= 9) {
-    return;
-  }
-
-  const char* utc = fields[1];
-  const char* status = fields[2];
-  const char* latRaw = fields[3];
-  const char* latHem = fields[4];
-  const char* lonRaw = fields[5];
-  const char* lonHem = fields[6];
-  const char* date = fields[9];
-
-  if (!status || status[0] != 'A') {
-    return;
-  }
-
-  if (!utc || strlen(utc) < 6 || !date || strlen(date) < 6) {
-    return;
-  }
-
-  uint8_t hh = 0, mm = 0, ss = 0;
-  uint8_t dd = 0, mo = 0, yy = 0;
-  if (!parseUInt2(utc + 0, hh) || !parseUInt2(utc + 2, mm) || !parseUInt2(utc + 4, ss)) {
-    return;
-  }
-  if (!parseUInt2(date + 0, dd) || !parseUInt2(date + 2, mo) || !parseUInt2(date + 4, yy)) {
-    return;
-  }
-
-  g_gps.utc.hour = hh;
-  g_gps.utc.minute = mm;
-  g_gps.utc.second = ss;
-  g_gps.utc.day = dd;
-  g_gps.utc.month = mo;
-  g_gps.utc.year = (uint16_t)(2000U + yy);
-  g_gps.hasValidUtc = true;
-  g_gps.lastUtcMs = millis();
-
-  double lat = 0.0;
-  double lon = 0.0;
-  if (parseNmeaCoordToDecimal(latRaw, latHem, true, lat) &&
-      parseNmeaCoordToDecimal(lonRaw, lonHem, false, lon)) {
-    g_gps.latitudeDeg = lat;
-    g_gps.longitudeDeg = lon;
-    g_gps.hasValidPosition = true;
-  }
-}
-
-static void processNmeaLine(char* line) {
-  if (!line || line[0] != '$') {
-    return;
-  }
-
-  g_gps.sawAnySentence = true;
-
-  char* star = strchr(line, '*');
-  if (star) {
-    *star = '\0';
-  }
-
-  char* fields[24] = {0};
-  int count = 0;
-  char* saveptr = nullptr;
-  char* tok = strtok_r(line, ",", &saveptr);
-  while (tok && count < 24) {
-    fields[count++] = tok;
-    tok = strtok_r(nullptr, ",", &saveptr);
-  }
-
-  if (count <= 0 || !fields[0]) {
-    return;
-  }
-
-  const char* header = fields[0];
-  size_t n = strlen(header);
-  if (n < 6) {
-    return;
-  }
-
-  const char* type = header + (n - 3);
-  if (strcmp(type, "GGA") == 0) {
-    parseGga(fields, count);
-  } else if (strcmp(type, "GSV") == 0) {
-    parseGsv(fields, count);
-  } else if (strcmp(type, "RMC") == 0) {
-    parseRmc(fields, count);
-  }
-}
-
-static void pollGpsSerial() {
-  while (g_gpsSerial.available() > 0) {
-    char c = (char)g_gpsSerial.read();
-    if (c == '\r') {
-      continue;
-    }
-    if (c == '\n') {
-      if (g_gpsLineLen > 0) {
-        g_gpsLine[g_gpsLineLen] = '\0';
-        processNmeaLine(g_gpsLine);
-        g_gpsLineLen = 0;
-      }
-      continue;
-    }
-
-    if (g_gpsLineLen + 1 < sizeof(g_gpsLine)) {
-      g_gpsLine[g_gpsLineLen++] = c;
-    } else {
-      g_gpsLineLen = 0;
-    }
-  }
-}
-
-static bool collectGpsTraffic(uint32_t windowMs) {
-  uint32_t start = millis();
-  bool sawBytes = false;
-  while ((uint32_t)(millis() - start) < windowMs) {
-    if (g_gpsSerial.available() > 0) {
-      sawBytes = true;
-    }
-    pollGpsSerial();
-    g_sd.update();
-    delay(2);
-  }
-  return sawBytes || g_gps.sawAnySentence;
-}
-
-static void initialGpsProbe() {
-  logf("GPS startup probe at %u baud", (unsigned)GPS_BAUD);
-  (void)collectGpsTraffic(kGpsStartupProbeMs);
-  logf("GPS probe complete: nmea=%s sats_used=%u sats_view=%u utc=%s",
-       g_gps.sawAnySentence ? "yes" : "no",
-       (unsigned)g_gps.satsUsed,
-       (unsigned)g_gps.satsInView,
-       g_gps.hasValidUtc ? "yes" : "no");
-}
-
-static IRAM_ATTR void onPpsEdge() {
-  g_ppsEdgeCount++;
-}
-
-static uint8_t bestSatelliteCount() {
-  return (g_gps.satsUsed > g_gps.satsInView) ? g_gps.satsUsed : g_gps.satsInView;
-}
-
-static bool ensureGpsLogPathReady() {
-  if (!g_sd.isMounted()) {
-    g_gpsPathReady = false;
-    return false;
-  }
-
-  if (g_gpsPathReady) {
-    return true;
-  }
-
-  if (!g_sd.ensureDirRecursive("/gps")) {
-    logf("Could not create /gps directory");
-    return false;
-  }
-
-  // Touch the log file so a clean SD card is prepared before first discipline event.
-  File f = SD.open("/gps/discipline_rtc.log", FILE_APPEND);
-  if (!f) {
-    logf("Could not open /gps/discipline_rtc.log for append");
-    return false;
-  }
-  f.close();
-
-  g_gpsPathReady = true;
-  return true;
-}
-
-static bool appendDisciplineLog(const DateTime& gpsUtc,
-                                bool havePriorRtc,
-                                int64_t rtcMinusGpsSeconds,
-                                uint8_t sats,
-                                uint32_t utcAgeMs,
-                                uint32_t ppsEdges,
-                                char* outTs,
-                                size_t outTsLen) {
-  if (!ensureGpsLogPathReady()) {
-    logf("SD not mounted, skipping append to gps/discipline_rtc.log");
-    return false;
-  }
-
-  File f = SD.open("/gps/discipline_rtc.log", FILE_APPEND);
-  if (!f) {
-    logf("Could not open /gps/discipline_rtc.log for append");
-    return false;
-  }
-
-  char ts[32];
-  formatUtcCompact(gpsUtc, ts, sizeof(ts));
-  if (outTs && outTsLen > 0) {
-    snprintf(outTs, outTsLen, "%s", ts);
-  }
-
-  char drift[40];
-  if (havePriorRtc) {
-    snprintf(drift, sizeof(drift), "%+lld s", (long long)rtcMinusGpsSeconds);
-  } else {
-    snprintf(drift, sizeof(drift), "RTC_unset");
-  }
-
-  char pos[64];
-  if (g_gps.hasValidPosition) {
-    snprintf(pos, sizeof(pos), "lat=%.6f lon=%.6f", g_gps.latitudeDeg, g_gps.longitudeDeg);
-  } else {
-    snprintf(pos, sizeof(pos), "lat=NA lon=NA");
-  }
-
-  char hdop[16];
-  if (g_gps.hdop > 0.0f) {
-    snprintf(hdop, sizeof(hdop), "%.1f", g_gps.hdop);
-  } else {
-    snprintf(hdop, sizeof(hdop), "NA");
-  }
-
-  char alt[16];
-  if (g_gps.hasValidAltitude) {
-    snprintf(alt, sizeof(alt), "%.1f", g_gps.altitudeM);
-  } else {
-    snprintf(alt, sizeof(alt), "NA");
-  }
-
-  char line[320];
-  snprintf(line,
-           sizeof(line),
-           "%s\t set RTC to GPS using 1PPS pulse-per-second discipline\t"
-           "rtc-gps drift=%s; sats=%u; %s; alt_m=%s; hdop=%s; utc_age_ms=%lu; pps_edges=%lu; "
-           "fw_epoch=%lu; fw_build_utc=%s",
-           ts,
-           drift,
-           (unsigned)sats,
-           pos,
-           alt,
-           hdop,
-           (unsigned long)utcAgeMs,
-           (unsigned long)ppsEdges,
-           (unsigned long)FW_BUILD_EPOCH,
-           FW_BUILD_UTC);
-
-  size_t wrote = f.println(line);
-  f.close();
-  if (wrote == 0) {
-    logf("Append write failed: /gps/discipline_rtc.log");
-    return false;
-  }
-  return true;
-}
-
-static bool gpsUtcIsFresh() {
-  if (!g_gps.hasValidUtc) {
-    return false;
-  }
-  return (uint32_t)(millis() - g_gps.lastUtcMs) <= 2000;
-}
-
-static bool waitForNextPps(uint32_t timeoutMs) {
-  uint32_t startCount = g_ppsEdgeCount;
-  uint32_t startMs = millis();
-  while ((uint32_t)(millis() - startMs) < timeoutMs) {
-    pollGpsSerial();
-    g_sd.update();
-    if (g_ppsEdgeCount != startCount) {
-      return true;
-    }
-    delay(2);
-  }
-  return false;
-}
-
-static void waitWithUpdates(uint32_t delayMs) {
-  uint32_t start = millis();
-  while ((uint32_t)(millis() - start) < delayMs) {
-    pollGpsSerial();
-    g_sd.update();
-    delay(10);
-  }
-}
-
-static void showNoTimeAndDelay() {
-  uint8_t sats = bestSatelliteCount();
-  char l3[24];
-  snprintf(l3, sizeof(l3), "Satellites: %u", (unsigned)sats);
-  oledShowLines("GPS time unavailable", "RTC NOT disciplined", l3, "Retry in 30 seconds");
-  logf("GPS UTC unavailable. satellites=%u. Waiting 30 seconds.", (unsigned)sats);
-  waitWithUpdates(kNoTimeDelayMs);
-}
-
-static bool disciplineRtcToGps() {
-  if (!gpsUtcIsFresh()) {
-    showNoTimeAndDelay();
-    return false;
-  }
-
-  DateTime priorRtc{};
-  bool lowV = false;
-  bool havePriorRtc = rtcRead(priorRtc, lowV);
-  if (havePriorRtc && (lowV || !isValidDateTime(priorRtc))) {
-    havePriorRtc = false;
-  }
-
-  DateTime gpsSnap = g_gps.utc;
-  if (!waitForNextPps(kPpsWaitTimeoutMs)) {
-    oledShowLines("GPS 1PPS missing", "RTC NOT disciplined", "Retry in 30 seconds");
-    logf("No 1PPS edge observed within timeout. Waiting 30 seconds.");
-    waitWithUpdates(kNoTimeDelayMs);
-    return false;
-  }
-
-  DateTime target = gpsSnap;
-  addOneSecond(target);
-
-  if (!rtcWrite(target)) {
-    oledShowLines("RTC write failed", "Could not set from GPS");
-    logf("RTC write failed");
-    return false;
-  }
-
-  int64_t driftSec = 0;
-  if (havePriorRtc) {
-    driftSec = toEpochSeconds(priorRtc) - toEpochSeconds(target);
-  }
-
-  uint8_t sats = bestSatelliteCount();
-  uint32_t utcAgeMs = (uint32_t)(millis() - g_gps.lastUtcMs);
-  uint32_t ppsEdges = g_ppsEdgeCount;
-  char tsCompact[32];
-  bool logOk = appendDisciplineLog(target,
-                                   havePriorRtc,
-                                   driftSec,
-                                   sats,
-                                   utcAgeMs,
-                                   ppsEdges,
-                                   tsCompact,
-                                   sizeof(tsCompact));
-
-  char utcLine[36];
-  char driftLine[36];
-  char logLine[36];
-  formatUtcHuman(target, utcLine, sizeof(utcLine));
-  if (havePriorRtc) {
-    snprintf(driftLine, sizeof(driftLine), "rtc-gps drift: %+lld s", (long long)driftSec);
-  } else {
-    snprintf(driftLine, sizeof(driftLine), "rtc-gps drift: RTC_unset");
-  }
-  snprintf(logLine, sizeof(logLine), "Log:%s sats:%u", logOk ? "ok" : "fail", (unsigned)sats);
-
-  oledShowLines("RTC disciplined to GPS", utcLine, driftLine, logLine, tsCompact);
-
-  logf("RTC disciplined to GPS with 1PPS. %s drift=%+llds lowV=%s",
-       utcLine,
-       (long long)driftSec,
-       lowV ? "yes" : "no");
-  return true;
-}
-
-void setup() {
-  Serial.begin(115200);
-  delay(kSerialDelayMs);
-
-  Serial.println("\r\n==================================================");
-  Serial.println("Exercise 11: Set RTC to GPS with 1PPS discipline");
-  Serial.println("==================================================");
-
-  if (!tbeam_supreme::initPmuForPeripherals(g_pmu, &Serial)) {
-    logf("PMU init failed");
-  }
-
-  Wire.begin(OLED_SDA, OLED_SCL);
-  g_oled.setI2CAddress(OLED_ADDR << 1);
-  g_oled.begin();
-  oledShowLines("Exercise 11", "RTC <- GPS (1PPS)", "Booting...");
-
-  SdWatcherConfig sdCfg{};
-  if (!g_sd.begin(sdCfg, nullptr)) {
-    logf("SD startup manager begin() failed");
-  }
-  (void)ensureGpsLogPathReady();
-
-#ifdef GPS_WAKEUP_PIN
-  pinMode(GPS_WAKEUP_PIN, INPUT);
-#endif
-#ifdef GPS_1PPS_PIN
-  pinMode(GPS_1PPS_PIN, INPUT);
-  attachInterrupt(digitalPinToInterrupt(GPS_1PPS_PIN), onPpsEdge, RISING);
-#endif
-
-  g_gpsSerial.setRxBufferSize(1024);
-  g_gpsSerial.begin(GPS_BAUD, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
-  logf("GPS UART started: RX=%d TX=%d baud=%u", GPS_RX_PIN, GPS_TX_PIN, (unsigned)GPS_BAUD);
-
-  oledShowLines("GPS startup probe", "Checking UTC + 1PPS");
-  initialGpsProbe();
-
-  g_nextDisciplineMs = millis();
-}
-
-void loop() {
-  pollGpsSerial();
-  g_sd.update();
-
-  if (g_sd.consumeMountedEvent()) {
-    g_gpsPathReady = false;
-    (void)ensureGpsLogPathReady();
-  }
-  if (g_sd.consumeRemovedEvent()) {
-    g_gpsPathReady = false;
-  }
-
-  uint32_t now = millis();
-  if ((int32_t)(now - g_nextDisciplineMs) >= 0) {
-    bool ok = disciplineRtcToGps();
-    g_nextDisciplineMs = now + (ok ? kLoopMsDiscipline : kNoTimeDelayMs);
-  }
-
-  delay(5);
-}