diff --git a/exercises/25_motioncal_tbeam/README.md b/exercises/25_motioncal_tbeam/README.md
index 66a8997..86451bc 100644
--- a/exercises/25_motioncal_tbeam/README.md
+++ b/exercises/25_motioncal_tbeam/README.md
@@ -1,59 +1,225 @@
 # Exercise 25: MotionCal T-Beam Bridge
 
-Streams the T-Beam Supreme QMC6310 magnetometer in the ASCII format accepted by
-Paul Stoffregen's MotionCal desktop tool.
+This PlatformIO project turns a LilyGO T-Beam Supreme into a serial bridge for Paul Stoffregen's MotionCal desktop calibration tool.
 
-https://github.com/PaulStoffregen/MotionCal.git (fetch)
+The firmware reads the onboard QMC magnetometer through SensorLib and streams MotionCal-compatible ASCII `Raw:` lines over USB serial. MotionCal can then estimate both hard-iron offsets and the soft-iron correction matrix for the board.
 
-See https://github.com/PaulStoffregen/MotionCal/issues/25 for Gentoo build tricks.
+![](MotionCal_2026-04-25_11-22.png)
+## Hardware
 
-MotionCal expects:
+Target board:
+
+```text
+LilyGO T-Beam Supreme / ESP32-S3
+QMC6310/QMC5883-family magnetometer
+SH1106 OLED display
+```
+
+The firmware probes these magnetometer I2C addresses:
+
+```text
+0x1C  QMC6310U
+0x3C  QMC6310N
+0x2C  QMC5883P
+```
+
+The default PlatformIO environment is `cy`, with additional board labels available in `platformio.ini`:
+
+```text
+amy bob cy dan ed flo guy
+```
+
+## Serial Format
+
+MotionCal expects lines in this format:
 
 ```text
 Raw:accel_x,accel_y,accel_z,gyro_x,gyro_y,gyro_z,mag_x,mag_y,mag_z
 ```
 
-This exercise only has a magnetometer, so it sends a stationary accelerometer
-placeholder and zero gyro:
+This bridge only has a magnetometer, so it sends fixed placeholder accel/gyro values:
 
 ```text
 Raw:0,0,8192,0,0,0,mag_x,mag_y,mag_z
 ```
 
-The magnetic values are converted from SensorLib Gauss readings into MotionCal's
-integer units where 1 count is 0.1 microtesla.
+The placeholder values mean:
+
+```text
+accel = 0,0,8192   approximately stationary upright in MotionCal's count convention
+gyro  = 0,0,0      no gyro data supplied
+mag   = live QMC magnetometer data
+```
+
+## Magnetometer Units
+
+SensorLib returns QMC magnetometer readings in Gauss. The firmware converts them like this:
+
+```text
+1 gauss = 100 microtesla
+MotionCal count = microtesla * 10
+1 MotionCal count = 0.1 microtesla
+```
+
+So a streamed value like this:
+
+```text
+Raw:0,0,8192,0,0,0,-1735,428,793
+```
+
+means:
+
+```text
+X = -1735 counts = -173.5 uT = -1.735 gauss
+Y =   428 counts =   42.8 uT =  0.428 gauss
+Z =   793 counts =   79.3 uT =  0.793 gauss
+```
+
+These are MotionCal-compatible integer counts, not raw QMC register values.
 
 ## Build
 
+Activate the Python environment that contains PlatformIO:
+
 ```sh
-cd /usr/local/src/microreticulum/microReticulumTbeam/exercises/25_motioncal_tbeam
-source /home/jlpoole/rnsenv/bin/activate
+source /home/jlpoole/pioenv/bin/activate
+```
+
+Build the default environment:
+
+```sh
+cd /usr/local/src/microReticulumTbeam/exercises/25_motioncal_tbeam
 pio run
 ```
 
+Build a specific board label:
+
+```sh
+pio run -e dan
+```
+
 ## Upload
 
+Upload the default environment:
+
 ```sh
-source /home/jlpoole/rnsenv/bin/activate
+source /home/jlpoole/pioenv/bin/activate
+cd /usr/local/src/microReticulumTbeam/exercises/25_motioncal_tbeam
 pio run -t upload
 ```
 
-Use a specific board environment if needed:
+Upload a specific board label:
 
 ```sh
-pio run -e guy -t upload
+pio run -e dan -t upload
 ```
 
-## MotionCal
+## Serial Monitor
 
-Build and run MotionCal as before:
+After flashing, monitor the USB serial stream at 115200 baud:
+
+```sh
+pio device monitor -b 115200 --port /dev/ttytDAN
+```
+
+Expected boot/status output includes lines like:
+
+```text
+exercise=Exercise 25 MotionCal T-Beam bridge
+serial_format=Raw:accel_x,accel_y,accel_z,gyro_x,gyro_y,gyro_z,mag_x,mag_y,mag_z
+mag_units=MotionCal integer counts, 1 count = 0.1 uT
+magnetometer_init=ok label=QMC6310U addr=0x1C chip=0x..
+```
+
+Expected streaming output looks like:
+
+```text
+Raw:0,0,8192,0,0,0,-1578,447,1266
+Raw:0,0,8192,0,0,0,-1583,438,1258
+Raw:0,0,8192,0,0,0,-1585,442,1250
+```
+
+If the firmware prints `read_fail` or `overflow` status lines, check I2C wiring/power and the configured magnetometer full-scale range.
+
+## Running MotionCal
+
+Build MotionCal if needed:
 
 ```sh
 cd /usr/local/src/MotionCal
 make WXCONFIG=wx-config LDFLAGS="-lglut -lGLU -lGL -lm"
+```
+
+Run it:
+
+```sh
+cd /usr/local/src/MotionCal
 GDK_BACKEND=x11 ./MotionCal
 ```
 
-Select the T-Beam USB serial port in MotionCal. The firmware also accepts
-MotionCal's 68-byte calibration packet and echoes `Cal1:` and `Cal2:` lines so
-MotionCal can confirm the send.
+Then select the T-Beam USB serial port in MotionCal.
+
+Move and rotate the T-Beam through as many orientations as possible. The goal is to cover the sphere well, not just wave it flat on the table. Better 3D coverage improves both hard-iron and soft-iron calibration.
+
+## Saving Calibration
+
+MotionCal computes:
+
+```text
+magnetic_offset_uT       hard-iron offset, in microtesla
+magnetic_mapping_matrix  inverse soft-iron correction matrix
+magnetic_field_uT        fitted local field magnitude
+```
+
+Example:
+
+```text
+magnetic_offset_uT=-172.96843,43.0260162,78.8941956
+magnetic_field_uT=52.4668198
+magnetic_mapping_matrix=
+  0.943139076 0.0439298451 0.0595370531
+  0.0439298451 1.04979992 -0.0347476006
+  0.0595370531 -0.0347476006 1.01706612
+```
+
+The firmware also accepts MotionCal's 68-byte calibration packet and echoes `Cal1:` and `Cal2:` lines so MotionCal can confirm the send.
+
+## Applying Calibration
+
+MotionCal's calibration model is:
+
+```text
+mag_uT = raw_motioncal_counts * 0.1
+centered = mag_uT - magnetic_offset_uT
+corrected = magnetic_mapping_matrix * centered
+```
+
+Hard iron moves the center of the magnetometer cloud back to zero. Soft iron transforms the ellipsoid-shaped cloud back toward a sphere.
+
+## Troubleshooting
+
+If MotionCal does not show points:
+
+```text
+Confirm the serial port is correct.
+Confirm baud is 115200.
+Confirm monitor output contains Raw: lines.
+Close any serial monitor before opening the port in MotionCal.
+```
+
+If the values look 10x different from a notebook or script:
+
+```text
+The notebook/script may be using MotionCal counts.
+MotionCal's saved magnetic_offset_uT is already in microtesla.
+Convert counts to uT with: uT = counts * 0.1
+```
+
+If the fit is poor:
+
+```text
+Collect more orientations.
+Rotate around all axes.
+Keep the board away from steel, speakers, motors, magnets, and high-current wiring.
+Try a different location and repeat the calibration.
+```
diff --git a/exercises/25_motioncal_tbeam/lib/SensorLib b/exercises/25_motioncal_tbeam/lib/SensorLib
new file mode 120000
index 0000000..74d66cb
--- /dev/null
+++ b/exercises/25_motioncal_tbeam/lib/SensorLib
@@ -0,0 +1 @@
+/usr/local/src/LilyGo-LoRa-Series/lib/SensorLib
\ No newline at end of file
diff --git a/exercises/25_motioncal_tbeam/platformio.ini b/exercises/25_motioncal_tbeam/platformio.ini
index f004814..b11f1b5 100644
--- a/exercises/25_motioncal_tbeam/platformio.ini
+++ b/exercises/25_motioncal_tbeam/platformio.ini
@@ -16,14 +16,17 @@ lib_deps =
   olikraus/U8g2@^2.36.4
   lewisxhe/XPowersLib@0.3.3
 
+
+; MOTIONCAL_MAG_RANGE_G must be either 2 or 8 (less precision)
 build_flags =
   -I ../../shared/boards
   -I ../../external/microReticulum_Firmware
-  -I ../../../../LilyGo-LoRa-Series/lib/SensorLib/src
+  -I ../../../LilyGo-LoRa-Series/lib/SensorLib/src
   -D BOARD_MODEL=BOARD_TBEAM_S_V1
   -D OLED_SDA=17
   -D OLED_SCL=18
   -D OLED_ADDR=0x3C
+  -D MOTIONCAL_MAG_RANGE_G=2
   -D ARDUINO_USB_MODE=1
   -D ARDUINO_USB_CDC_ON_BOOT=1
 
diff --git a/exercises/25_motioncal_tbeam/src/main.cpp b/exercises/25_motioncal_tbeam/src/main.cpp
index 60de5ee..517a3a9 100644
--- a/exercises/25_motioncal_tbeam/src/main.cpp
+++ b/exercises/25_motioncal_tbeam/src/main.cpp
@@ -35,15 +35,30 @@ namespace {
 #define OLED_ADDR 0x3C
 #endif
 
+#ifndef MOTIONCAL_MAG_RANGE_G
+#define MOTIONCAL_MAG_RANGE_G 8
+#endif
+
 #define STR_INNER(x) #x
 #define STR(x) STR_INNER(x)
 
+#if MOTIONCAL_MAG_RANGE_G == 2
+static constexpr MagFullScaleRange kMagFullScaleRange = MagFullScaleRange::FS_2G;
+static constexpr const char* kMagRangeLabel = "FS2G";
+#elif MOTIONCAL_MAG_RANGE_G == 8
+static constexpr MagFullScaleRange kMagFullScaleRange = MagFullScaleRange::FS_8G;
+static constexpr const char* kMagRangeLabel = "FS8G";
+#else
+#error "MOTIONCAL_MAG_RANGE_G must be 2 or 8"
+#endif
+
 static constexpr const char* kExerciseName = "Exercise 25";
 static constexpr const char* kBoardId = BOARD_ID;
 static constexpr const char* kNodeLabel = NODE_LABEL;
-static constexpr const char* kBuildUtc = STR(FW_BUILD_UTC);
+static constexpr const char* kFirmwareVersion = STR(FW_BUILD_UTC);
 static constexpr uint32_t kSampleIntervalMs = 40;
 static constexpr uint32_t kDisplayIntervalMs = 250;
+static constexpr uint32_t kStatusIntervalMs = 1000;
 static constexpr uint8_t kMagCandidateCount = 3;
 static constexpr uint8_t kMagCandidates[kMagCandidateCount] = {0x1C, 0x3C, 0x2C};
 static constexpr uint16_t kCalibrationPacketSize = 68;
@@ -61,7 +76,10 @@ uint8_t g_magChipId = 0;
 char g_magLabel[16] = "UNKNOWN";
 uint32_t g_lastSampleMs = 0;
 uint32_t g_lastDisplayMs = 0;
+uint32_t g_lastStatusMs = 0;
 uint32_t g_sampleCount = 0;
+uint32_t g_readFailCount = 0;
+uint32_t g_overflowCount = 0;
 int16_t g_lastMagCounts[3] = {0, 0, 0};
 float g_lastMagUt[3] = {0.0f, 0.0f, 0.0f};
 
@@ -106,18 +124,20 @@ void drawLines(const char* l1,
                const char* l2 = nullptr,
                const char* l3 = nullptr,
                const char* l4 = nullptr,
-               const char* l5 = nullptr) {
+               const char* l5 = nullptr,
+               const char* l6 = nullptr) {
   if (!g_displayReady) {
     return;
   }
 
   g_oled.clearBuffer();
-  g_oled.setFont(u8g2_font_6x12_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.setFont(u8g2_font_5x8_tf);
+  if (l1) g_oled.drawUTF8(0, 10, l1);
+  if (l2) g_oled.drawUTF8(0, 20, l2);
+  if (l3) g_oled.drawUTF8(0, 30, l3);
+  if (l4) g_oled.drawUTF8(0, 40, l4);
+  if (l5) g_oled.drawUTF8(0, 50, l5);
+  if (l6) g_oled.drawUTF8(0, 60, l6);
   g_oled.sendBuffer();
 }
 
@@ -129,7 +149,7 @@ void initDisplay() {
   g_oled.begin();
   g_oled.setPowerSave(0);
   g_displayReady = true;
-  drawLines(kExerciseName, "MotionCal Bridge", kBoardId, "starting...");
+  drawLines(kExerciseName, kFirmwareVersion, kBoardId, "MotionCal Bridge", "starting...");
 }
 
 bool probeI2cAddr(TwoWire& wire, uint8_t addr) {
@@ -171,7 +191,7 @@ bool initMagnetometer() {
   g_magChipId = g_qmc.getChipID();
   return g_qmc.configMagnetometer(
       OperationMode::CONTINUOUS_MEASUREMENT,
-      MagFullScaleRange::FS_2G,
+      kMagFullScaleRange,
       100.0f,
       MagOverSampleRatio::OSR_4,
       MagDownSampleRatio::DSR_1);
@@ -179,9 +199,10 @@ bool initMagnetometer() {
 
 void printBootSummary() {
   Serial.printf("exercise=%s MotionCal T-Beam bridge\r\n", kExerciseName);
-  Serial.printf("board_id=%s node_label=%s build=%s\r\n", kBoardId, kNodeLabel, kBuildUtc);
+  Serial.printf("board_id=%s node_label=%s build=%s\r\n", kBoardId, kNodeLabel, kFirmwareVersion);
   Serial.printf("serial_format=Raw:accel_x,accel_y,accel_z,gyro_x,gyro_y,gyro_z,mag_x,mag_y,mag_z\r\n");
   Serial.printf("mag_units=MotionCal integer counts, 1 count = 0.1 uT\r\n");
+  Serial.printf("mag_range=%s\r\n", kMagRangeLabel);
 }
 
 void streamMotionCalRaw(const MagnetometerData& data) {
@@ -208,10 +229,10 @@ void updateDisplay() {
   char line4[28];
   char line5[28];
 
-  snprintf(line3, sizeof(line3), "%s 0x%02X id 0x%02X", g_magLabel, g_magAddress, g_magChipId);
   snprintf(line4, sizeof(line4), "%6.1f %6.1f", g_lastMagUt[0], g_lastMagUt[1]);
   snprintf(line5, sizeof(line5), "Z:%6.1f N:%lu", g_lastMagUt[2], (unsigned long)g_sampleCount);
-  drawLines(kExerciseName, "MotionCal Raw stream", line3, line4, line5);
+  snprintf(line3, sizeof(line3), "%s %s 0x%02X", kMagRangeLabel, g_magLabel, g_magAddress);
+  drawLines(kExerciseName, kFirmwareVersion, line3, line4, line5, "Raw stream");
 }
 
 void printCalibrationEcho(const float* values) {
@@ -293,7 +314,7 @@ void appSetup() {
 
   if (!tbeam_supreme::initPmuForPeripherals(g_pmu, &Serial)) {
     Serial.println("pmu_init=failed");
-    drawLines(kExerciseName, "PMU init failed", kBoardId, "see serial");
+    drawLines(kExerciseName, kFirmwareVersion, "PMU init failed", kBoardId, "see serial");
     return;
   }
   Serial.println("pmu_init=ok");
@@ -301,15 +322,16 @@ void appSetup() {
   g_magReady = initMagnetometer();
   if (!g_magReady) {
     Serial.println("magnetometer_init=failed");
-    drawLines(kExerciseName, "MAG init failed", kBoardId, "see serial");
+    drawLines(kExerciseName, kFirmwareVersion, "MAG init failed", kBoardId, "see serial");
     return;
   }
 
   Serial.printf("magnetometer_init=ok label=%s addr=0x%02X chip=0x%02X\r\n",
                 g_magLabel, g_magAddress, g_magChipId);
-  drawLines(kExerciseName, "MotionCal Bridge", g_magLabel, "streaming Raw...");
+  drawLines(kExerciseName, kFirmwareVersion, "MotionCal Bridge", g_magLabel, "streaming Raw...");
   g_lastSampleMs = millis();
   g_lastDisplayMs = millis();
+  g_lastStatusMs = millis();
 }
 
 void appLoop() {
@@ -324,7 +346,11 @@ void appLoop() {
   if ((uint32_t)(now - g_lastSampleMs) >= kSampleIntervalMs) {
     g_lastSampleMs = now;
     MagnetometerData data;
-    if (g_qmc.readData(data) && !data.overflow) {
+    if (!g_qmc.readData(data)) {
+      ++g_readFailCount;
+    } else if (data.overflow) {
+      ++g_overflowCount;
+    } else {
       streamMotionCalRaw(data);
     }
   }
@@ -334,6 +360,16 @@ void appLoop() {
     updateDisplay();
   }
 
+  if ((uint32_t)(now - g_lastStatusMs) >= kStatusIntervalMs) {
+    g_lastStatusMs = now;
+    if (g_readFailCount > 0 || g_overflowCount > 0) {
+      Serial.printf("motioncal_status=samples:%lu read_fail:%lu overflow:%lu\r\n",
+                    (unsigned long)g_sampleCount,
+                    (unsigned long)g_readFailCount,
+                    (unsigned long)g_overflowCount);
+    }
+  }
+
   delay(1);
 }