calibrate enclosure motion outputs

README.md

@@ -8,7 +8,8 @@ This milestone does four things:
 1. Detects and verifies both sensors by their identification registers.
 2. Configures each sensor for a nominal 100 Hz raw output rate.
 3. Emits timestamped, sensor-native raw readings over the XIAO USB connection.
-4. Maps both sensors into a shared enclosure coordinate frame for validation.
+4. Maps both sensors into a shared enclosure coordinate frame and emits both raw
+   and calibrated readings.
 
 BLE transport and phone-side storage come after the wired sensor path is proven.
 
@@ -48,7 +49,11 @@ enclosure Y = -native X
 enclosure Z =  native Z
 ```
 
-No software calibration, software filtering, or sensor fusion is performed yet.
+Software calibration is applied after enclosure-axis mapping. Accelerometer
+offset and per-axis scale were measured with a six-face enclosure test. Gyroscope
+zero-rate bias and polarity were measured; its 17.5 mdps/LSB scale remains the
+nominal datasheet value. Sensor-native and mapped raw counts remain in every
+record for diagnostics. No software filtering or sensor fusion is performed yet.
 
 The ESP32-C3 polls at exactly 100 Hz, but each sensor has an independent internal
 sample clock. The status registers are read immediately before each XYZ read so a
@@ -79,13 +84,14 @@ Exit the serial monitor with `Ctrl-]`.
 After startup metadata, records use CSV:
 
 ```text
-sequence,poll_timestamp_us,accel_x_raw,accel_y_raw,accel_z_raw,gyro_x_raw,gyro_y_raw,gyro_z_raw,accel_native_x_raw,accel_native_y_raw,accel_native_z_raw,gyro_native_x_raw,gyro_native_y_raw,gyro_native_z_raw,accel_int_source,gyro_status,loop_overrun_count
+sequence,poll_timestamp_us,accel_x_raw,accel_y_raw,accel_z_raw,gyro_x_raw,gyro_y_raw,gyro_z_raw,accel_x_mg,accel_y_mg,accel_z_mg,gyro_x_mdps,gyro_y_mdps,gyro_z_mdps,accel_native_x_raw,accel_native_y_raw,accel_native_z_raw,gyro_native_x_raw,gyro_native_y_raw,gyro_native_z_raw,accel_int_source,gyro_status,loop_overrun_count
 ```
 
 `poll_timestamp_us` is the ESP32-C3 monotonic time immediately before the status
 and data reads. It is not the sensors' physical sample time. The axes in the first
-six sample columns use the enclosure frame above. Native columns remain available
-for diagnostics.
+six sample columns use the enclosure frame above. Calibrated acceleration is in
+integer milligravity (`mg`), and bias-corrected angular rate is in integer
+millidegrees per second (`mdps`). Native columns remain available for diagnostics.
 
 Status bits: