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The IMU board does fit a 3 axis gyroscope + a 3 axis magnetometer + 3 axis accelerometer.
- The LSM6DSOx or LSM6DS33 contains a gyroscope and an accelerometer.
- The LIS3MDL is a 3 axis magnetometer.
This implementation of the 9DoF libraries use default settings matching robotic expectation (like it was for the Pico-Zumo Robot) with:
- Raw values returned as int16 (so with between -32,768 to 32,767)
- Accelerometer with range of +/- 2G full scale
- Gyroscope with range of +/- 245dps full scale
- Magnetometer range of +/- 4 Gauss full scale
The code of this IMU is coming from our project micropython-zumo-robot using exactly the same components that this breakout.
The library must be copied on the MicroPython board before using the examples.
On a WiFi capable plateform:
>>> import mip
>>> mip.install("github:mchobby/esp8266-upy/imu-a")
Or via the mpremote utility :
mpremote mip install github:mchobby/esp8266-upy/imu-a
The imu_a.py and compass.py must be copied on the board filesystem before running the examples.
The examples/test_imu.py read all the data coming from the sensors display the results on REPL session.
from machine import I2C, Pin
from imu_a import IMU_A # 9DoF Imu based on LSM6DS33 + LIS3MDL
import time
i2c = I2C(0, sda=Pin.board.GP8, scl=Pin.board.GP9 )
imu = IMU_A( i2c )
while True:
imu.read()
print( "Acc= %6i, %6i, %6i : Mag= %6i, %6i, %6i : Gyro= %6i, %6i, %6i " % (imu.a.values+imu.m.values+imu.g.values) )
time.sleep( 0.5 )Which produce the following raw value still must be translated to units based on sensor configuration (see intro):
Acc= 4867, -8612, 13667 : Mag= -583, 2324, -3512 : Gyro= 16, -73, 69
Acc= 4882, -8605, 13668 : Mag= -513, 2363, -3533 : Gyro= -9, -68, 65
Acc= 4872, -8614, 13661 : Mag= -568, 2373, -3518 : Gyro= -21, -70, 58
Acc= 4874, -8611, 13670 : Mag= -560, 2355, -3481 : Gyro= 7, -74, 67
Acc= 4875, -8616, 13667 : Mag= -566, 2337, -3555 : Gyro= -14, -69, 68
Acc= 4876, -8612, 13664 : Mag= -529, 2345, -3511 : Gyro= -8, -76, 68
The Compass class is used to calculate north position by using the X & Y axis of the magnetometer.
The examples/test_compass.py configure the magnetometer for Heading detect. After a short calibration stage where you should move the magnetometer in every direction to enbale the calibration to find minima & maxima on the both axis.
from machine import I2C, Pin
from imu_a import IMU_A
from compass import Compass
import time
i2c = I2C(0, sda=Pin.board.GP8, scl=Pin.board.GP9 )
imu = IMU_A( i2c ) # Start with auto detection
compass = Compass( imu, samples=120 )
print("Starting calibration...")
print(" rotate it on himself to find compass min and max")
compass.calibrate()
print("calibration done")
print( 'Compass min: %s ' % compass.min )
print( 'Compass max: %s ' % compass.max )
while True:
heading = compass.average_heading()
print( 'Heading %s degrees' % heading )
time.sleep( 0.5 )