P R / Mbed 2 deprecated Xadow-M0_Xadow-OLED_Accelerometer

A quick and dirty demo of the Xadow M0 acceleromoeter values displayed on the Xadow OLED 0.96" (using the SSD1308 128x64 OLED Driver with I2C interface library).

Dependencies:   mbed SSD1308_128x64_I2C_opt XadowGPS BMP180 ADXL345_I2C MPU9250 USBDevice

Files at this revision

API Documentation at this revision

Revision 8:4e8991196bb8, committed 2019-02-23

Comitter:
ruevs
Date:
Sat Feb 23 18:07:47 2019 +0000
Parent:
7:4931dbfbc042
Child:
9:310663c014d8
Commit message:
Fix the call to MahonyQuaternionUpdate to reflect the proper orientation of the accelerometer and gyroscope axis in the MPU9250.

Changed in this revision

main.cpp Show annotated file Show diff for this revision Revisions of this file 
--- a/main.cpp	Fri Oct 26 06:35:24 2018 +0000
+++ b/main.cpp	Sat Feb 23 18:07:47 2019 +0000
@@ -190,9 +190,18 @@
         sum += deltat;
         sumCount++;
     
+        // Sensors x (y)-axis of the accelerometer/gyro is aligned with the y (x)-axis of the magnetometer;
+        // the magnetometer z-axis (+ down) is misaligned with z-axis (+ up) of accelerometer and gyro!
+        // We have to make some allowance for this orientation mismatch in feeding the output to the quaternion filter.
+        // We will assume that +y accel/gyro is North, then x accel/gyro is East. So if we want te quaternions properly aligned
+        // we need to feed into the madgwick function Ay, Ax, -Az, Gy, Gx, -Gz, Mx, My, and Mz. But because gravity is by convention
+        // positive down, we need to invert the accel data, so we pass -Ay, -Ax, Az, Gy, Gx, -Gz, Mx, My, and Mz into the Madgwick
+        // function to get North along the accel +y-axis, East along the accel +x-axis, and Down along the accel -z-axis.
+        // This orientation choice can be modified to allow any convenient (non-NED) orientation convention.
+        // This is ok by aircraft orientation standards!  
         // Pass gyro rate as rad/s
-        // mpu9250.MadgwickQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f,  my,  mx, mz);
-        mpu9250.MahonyQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f, my, mx, mz);
+        // mpu9250.MadgwickQuaternionUpdate(-ay, -ax, az, gy*PI/180.0f, gx*PI/180.0f, -gz*PI/180.0f,  mx,  my, mz);
+        mpu9250.MahonyQuaternionUpdate(-ay, -ax, az, gy*PI/180.0f, gx*PI/180.0f, -gz*PI/180.0f, mx, my, mz);
 
 
         // Serial print and/or display at 1.5 s rate independent of data rates