Acessing the MAG-3110 on the M5STACK FIRE

AmbiDextrose

Gentlefolk,

Greetings. I am trying to access the MAG-3110 magnetometer on the M5STACK FIRE but have been unsuccessful so far. However, I am able to access the MPU-6050 without any discernible issues.

I have a Windows environment and am using MicroPython. I've tried a number of MicroPython firmware and the latest one I'm using is m5cloud-psram-20180516-v0.4.0.bin. I am also using M5Burner for Windows to flash the M5STACK FIRE.

I've tried to reverse-engineer a number of Python modules in order to see if I can access the magnetometer via REPL. Here are some of the results I have obtained:

from machine import I2C

i2c = I2C(scl=Pin(22), sda=Pin(21), speed=400000)

i2c.scan()
[14, 104, 117] # addr 104 is the MPU-6050 and 14 should be the MAG-3110

struct.unpack("B", i2c.readfrom_mem(14, 7, 1)) # check who_am_i register on device with addr 14
(196,) # is this the correct response (0xC4) according to the spec sheet

i2c.writeto_mem(14, 16, 1) # set operation mode, RW register according to the spec sheet (CTRL_REG1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: object with buffer protocol required

i2c.writeto_mem(14 17, 1) # try the other register, RW register according to the spec sheet (CTRL_REG1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: object with buffer protocol required

Note that the same things happen when I try to access address 117 although I get a different response WHO_AM_I (i.e., 0x80 instead of 0xC4). If I try to read the data registers, the contents do not change even if I aggressively move the M5STACK FIRE. I am, however, able to get accelerometer and gyroscope readings.

Has anyone else encountered this or have successfully accessed the magnetometer on the M5STACK FIRE?

Best regards.

lukasmaximus

Hi there you can try this code.

from m5stack import lcd, buttonA
from mpu9250 import MPU9250
from time import sleep_ms
from machine import I2C

i2c = I2C(sda = 21, scl = 22)
imu = MPU9250(i2c)

lcd.clear()
lcd.font(lcd.FONT_Small)
lcd.setTextColor(lcd.WHITE, lcd.BLACK)

while not buttonA.isPressed():
mag = imu.magnetic
print("MAG: {:8.3f} {:8.3f} {:8.3f}".format(mag[0], mag[1], mag[2]))
print('')
lcd.print("MAG:{:+7.2f} {:+7.2f} {:+7.2f}".format(mag[0], mag[1], mag[2]), lcd.CENTER, 60)
sleep_ms(20)

lcd.print('Exit.', 0, 100)

Remember that there are magnets in the base of the m5 core, so maybe best to remove it if you don't want any interference in the magnetometer reading

AmbiDextrose

Hey Lukas,

This won't work. The mpu9250 module expects to find an MPU6500 accelerometer so even instantiating an mpu9250 object will fail during init(). Even if I remove the part of the code that checks for the MPU6500, instantiation will still fail when it attempts to initialize the magnetometer by writing to one of it's registers.