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Rotate IMU data to support standard axes orientation in new FlixPeriph

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Oleg Kalachev 2024-12-11 06:17:37 +03:00
parent fcb426a16f
commit 77effa5577
5 changed files with 93 additions and 88 deletions
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8
README.md
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@ -135,13 +135,13 @@ Complete diagram is Work-in-Progress.
### IMU placement
Required IMU orientation on the drone is **FLU** (Forward, Left, Up)⁷:
Default IMU orientation in the code is **LFD** (Left-Forward-Down):
<img src="docs/img/flu.svg" width=400 alt="GY-91 axis">
<img src="docs/img/gy91-lfd.svg" width=400 alt="GY-91 axes">
In case of using **FRD** orientation (Forward, Right, Down), use [the code for rotation](https://gist.github.com/okalachev/713db47e31bce643dbbc9539d166ce98).
In case of using other IMU orientation, modify the `rotateIMU` function in the `imu.ino` file.
*⁷ — This X/Y/Z IMU axis orientation is used in the Flix IMU library, internal accel/gyro/mag axes differ.*
See [FlixPeriph documentation](https://github.com/okalachev/flixperiph?tab=readme-ov-file#imu-axes-orientation) to learn axis orientation of other IMU boards.
## Version 0

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docs/troubleshooting.md
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@ -21,6 +21,7 @@ Do the following:
* **Check the IMU data**. Perform `imu` command, check raw accelerometer and gyro output. The output should change as you move the drone.
* **Calibrate the accelerometer.** if is wasn't done before. Perform `ca` command and put the results to `imu.ino` file.
* **Check the attitude estimation**. Connect to the drone using QGroundControl. Rotate the drone in different orientations and check if the attitude estimation shown in QGroundControl is correct.
* **Check the IMU orientation is set correctly**. If the attitude estimation is rotated, make sure `rotateIMU` function is defined correctly in `imu.ino` file.
* **Check the motors**. Perform the following commands using Serial Monitor:
* `mfr` — should rotate front right motor (counter-clockwise).
* `mfl` — should rotate front left motor (clockwise).

13
flix/imu.ino
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@ -2,9 +2,6 @@
// Repository: https://github.com/okalachev/flix
// Work with the IMU sensor
// IMU is oriented FLU (front-left-up) style.
// In case of FRD (front-right-down) orientation of the IMU, use this code:
// https://gist.github.com/okalachev/713db47e31bce643dbbc9539d166ce98.
#include <SPI.h>
#include <MPU9250.h>
@ -45,6 +42,16 @@ void readIMU() {
// apply scale and bias
acc = (acc - accBias) / accScale;
gyro = gyro - gyroBias;
// rotate
rotateIMU(acc);
rotateIMU(gyro);
}
void rotateIMU(Vector& data) {
// Rotate from LFD to FLU
// NOTE: In case of using other IMU orientation, change this line:
data = Vector(data.y, data.x, -data.z);
// Axes orientation for various boards: https://github.com/okalachev/flixperiph#imu-axes-orientation
}
void calibrateGyro() {