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+# wemo-mpu9250-gps
+
+Interfacing MPU9250 (and gps module) to WEMOS D1 MINI PRO
+
+## Requirement for embedding the webpages to the board
+
+To embed the html static page, the board must have at least 4MB Flash.
+The pages can be uploaded to the board using Arduino's LittleFS add-ons:
+https://github.com/earlephilhower/arduino-esp8266littlefs-plugin/releases
+
+## References
+
+It is almost impossible to develop this project without helps / references, especially from:
+
+1. [Magnetometer Calibration:kriswiner-mpu9250] (https://github.com/kriswiner/MPU9250)
+2. [Digital Motion Processing:sparkfun-mpu9250-dmp] (https://github.com/sparkfun/SparkFun_MPU-9250-DMP_Arduino_Library)
+3. [Tilt Compensation Based on DMP's Quaternion:linux-mpu9150] https://github.com/mlaurijsse/linux-mpu9150
+
+## Axes definition
+
+For tilt-compensation, axes alignment between modules and calculation angles is very important.
+This work uses this axes alignment:
+
+1. Accelerometer & gyroscope / DMP axes: 
+   - X axis direction (right wing down) = euler roll positive, 
+   - Y axis (nose down) = euler pitch negative,
+   - Z axis (counter clockwise) = euler yaw negative
+
+2. Magnetometer:
+   - X axis (nose down) = euler pitch negative,
+   - Y axis (right wing down) = euler roll positive,
+   - Z axis (clockwise) = euler yaw positive
+
+Summary:
+   - X-accel = Y-magnetometer => (positive)Roll
+   - Y-accel = X-magnetometer => (negative)Pitch
+   - Z-accel = (negative)Z-magnetometer => (negative)Yaw