Exercise 02 working: basic screen print out

exercises/02_oled_display/README.md

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+## Exercise 02: OLED Display
+
+This exercise demonstrates multiple OLED rendering patterns on the LilyGO T-Beam Supreme (SH1106).
+
+The firmware runs 3 demos in sequence, then shows a restart banner and repeats forever.
+
+## Demo Sequence
+
+### Demo 1: Scrolling Text
+- Shows `Hello #<n>` lines.
+- New lines are added below prior lines.
+- Up to 5 lines are visible; old lines roll off the top.
+
+### Demo 2: Fill Then Erase
+- Displays `Count 1` through `Count 10`.
+- Shows a short `Clearing screen...` message.
+- Erases the OLED to demonstrate explicit clear behavior.
+
+### Demo 3: Multi-Page Rotation
+- Rotates through 3 distinct text pages.
+- Each page has different content/layout to demonstrate refresh transitions.
+- Includes a changing packet counter field on one page.
+
+### Restart Banner
+- Shows `Restarting 3 demos` for 5 seconds.
+- Sequence restarts at Demo 1.
+
+## Expected Serial Output
+Serial output (115200) prints phase changes, for example:
+- `Demo 1/3: scrolling Hello #`
+- `Demo 2/3: clear screen after 10`
+- `Demo 3/3: three-page rotation`
+- `Restarting 3 demos`
+
+### Build
+From this directory:
+
+```bash
+source /home/jlpoole/rnsenv/bin/activate
+pio run -e node_a
+```
+
+### Upload
+Set your USB port:
+
+```bash
+source /home/jlpoole/rnsenv/bin/activate
+pio run -e node_a -t upload --upload-port /dev/ttyACM0
+```
+
+### Serial Monitor
+
+```bash
+screen /dev/ttyACM0 115200
+```

exercises/02_oled_display/platformio.ini

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+; 20260213 ChatGPT
+; $Id$
+; $HeadURL$
+
+[platformio]
+default_envs = node_a
+
+[env]
+platform = espressif32
+framework = arduino
+board = esp32-s3-devkitc-1
+monitor_speed = 115200
+lib_deps =
+  olikraus/U8g2@^2.36.4
+
+; Common build flags (pins from Meshtastic tbeam-s3-core variant.h)
+build_flags =
+  -D OLED_SDA=17
+  -D OLED_SCL=18
+  -D OLED_ADDR=0x3C
+  -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\"

exercises/02_oled_display/src/main.cpp

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+// 20260213 ChatGPT
+// $Id$
+// $HeadURL$
+
+#include <Arduino.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
+
+// LilyGO T-Beam Supreme uses SH1106 OLED on I2C.
+U8G2_SH1106_128X64_NONAME_F_HW_I2C oled(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
+
+static const uint8_t kMaxLines = 5;
+static String g_lines[kMaxLines];
+static uint32_t g_iteration = 1;
+static uint32_t g_pageCounter = 1;
+
+static void addLine(const String& line) {
+  for (uint8_t i = 0; i < kMaxLines - 1; ++i) {
+    g_lines[i] = g_lines[i + 1];
+  }
+  g_lines[kMaxLines - 1] = line;
+}
+
+static void drawLines() {
+  oled.clearBuffer();
+  oled.setFont(u8g2_font_6x10_tf);
+
+  const int yStart = 12;
+  const int yStep = 12;
+  for (uint8_t i = 0; i < kMaxLines; ++i) {
+    if (g_lines[i].length() == 0) {
+      continue;
+    }
+    oled.drawUTF8(0, yStart + (i * yStep), g_lines[i].c_str());
+  }
+  oled.sendBuffer();
+}
+
+static void clearLines() {
+  for (uint8_t i = 0; i < kMaxLines; ++i) {
+    g_lines[i] = "";
+  }
+}
+
+static void showCentered(const char* line1, const char* line2 = nullptr, const char* line3 = nullptr) {
+  oled.clearBuffer();
+  oled.setFont(u8g2_font_6x10_tf);
+
+  if (line1) oled.drawUTF8(0, 16, line1);
+  if (line2) oled.drawUTF8(0, 32, line2);
+  if (line3) oled.drawUTF8(0, 48, line3);
+
+  oled.sendBuffer();
+}
+
+static void demo1_scrollingHello() {
+  Serial.println("Demo 1/3: scrolling Hello #");
+  clearLines();
+  for (uint8_t i = 0; i < 10; ++i) {
+    String line = "Hello #" + String(g_iteration++);
+    addLine(line);
+    drawLines();
+    delay(1000);
+  }
+}
+
+static void demo2_clearAfterTen() {
+  Serial.println("Demo 2/3: clear screen after 10");
+  clearLines();
+  for (uint8_t i = 1; i <= 10; ++i) {
+    String line = "Count " + String(i);
+    addLine(line);
+    drawLines();
+    delay(500);
+  }
+
+  showCentered("Demo 2", "Clearing screen...");
+  delay(1000);
+  oled.clearDisplay();
+  oled.sendBuffer();
+  delay(1000);
+}
+
+static void drawPage(uint8_t page) {
+  oled.clearBuffer();
+  oled.setFont(u8g2_font_6x10_tf);
+
+  if (page == 0) {
+    oled.drawUTF8(0, 12, "Demo 3 - Page 1/3");
+    oled.drawUTF8(0, 28, "GPS: 37.7749 N");
+    oled.drawUTF8(0, 40, "LON: 122.4194 W");
+    oled.drawUTF8(0, 56, "Fix: 3D");
+  } else if (page == 1) {
+    oled.drawUTF8(0, 12, "Demo 3 - Page 2/3");
+    oled.drawUTF8(0, 28, "LoRa RSSI: -92 dBm");
+    oled.drawUTF8(0, 40, "LoRa SNR:  +8.5 dB");
+    oled.drawUTF8(0, 56, "Pkts: " );
+    oled.setCursor(38, 56);
+    oled.print(g_pageCounter++);
+  } else {
+    oled.drawUTF8(0, 12, "Demo 3 - Page 3/3");
+    oled.drawUTF8(0, 28, "Node: TBM-SUPREME");
+    oled.drawUTF8(0, 40, "Mode: Field Test");
+    oled.drawUTF8(0, 56, "OLED refresh demo");
+  }
+
+  oled.sendBuffer();
+}
+
+static void demo3_threePages() {
+  Serial.println("Demo 3/3: three-page rotation");
+  for (uint8_t round = 0; round < 3; ++round) {
+    drawPage(0);
+    delay(700);
+    drawPage(1);
+    delay(700);
+    drawPage(2);
+    delay(700);
+  }
+}
+
+static void showRestartBanner() {
+  Serial.println("Restarting 3 demos");
+  showCentered("Restarting 3 demos", "Cycle begins again", "in 5 seconds...");
+  delay(5000);
+}
+
+void setup() {
+  Serial.begin(115200);
+  delay(250);
+
+  Wire.begin(OLED_SDA, OLED_SCL);
+  oled.setI2CAddress(OLED_ADDR << 1); // U8g2 expects 8-bit address.
+  oled.begin();
+
+  oled.clearBuffer();
+  oled.setFont(u8g2_font_6x10_tf);
+  oled.drawUTF8(0, 12, "Exercise 02 OLED");
+  oled.sendBuffer();
+
+  Serial.println("Exercise 02: OLED display loop");
+  Serial.printf("OLED SDA=%d SCL=%d ADDR=0x%02X\r\n", OLED_SDA, OLED_SCL, OLED_ADDR);
+}
+
+void loop() {
+  demo1_scrollingHello();
+  demo2_clearAfterTen();
+  demo3_threePages();
+  showRestartBanner();
+}