QMC5883L/QMC5883P: Python class for the QMC5883L/QMC5883P Three-Axis Digital Compass IC

This is a very short and simple class. It uses the I2C bus for the interface.

Initial code by Sebastian Folz, M.Sc. at http://nobytes.blogspot.com/2018/03/qmc5883-magnetic-field-sensor.html

Types of QMC5883

There are two types of QMC5883 available on the market.

• QMC5883L - Have less range modes, maximum magnetic field range is 8G (800 uT). And maximum output rate is 200hz. Datasheet available @LCSC (https://datasheet.lcsc.com/szlcsc/QST-QMC5883L-TR_C192585.pdf)
• QMC5883P - Sensivity range is 30G. Accuracy overall is worser than in QMC5883L. Maximum output rate is 1.5khz. No temperature sensor. Datasheet available @LCSC (https://datasheet.lcsc.com/lcsc/2108072330_QST-QMC5883P_C2847467.pdf)

The chips have totally different PCB package. On the market available both variant, but if takes Arduino modules, mostly it will be QMC5883L (@see GY-273 modules) Register map of these chips are totally different.

Constructor

The both drivers uses the same interface (ie parent class) - mag_base. Could be selected, any of available driver QMC5883L or QMC5883P. Next examples use QMC5883P, but due to the same interface class could be replaced with QMC5883L

QMC5883 = QMC5883P(i2c [, temp_offset])

• i2c is an I2C object which has to be created by the caller.
• temp_offset specifies the offset to the temperature, as returned by the method (only in QMC5883L) read_scaled. The unit is °C, the default is 50 °C.

Methods

(x, y, z, t) = QMC5883.read_raw()

Return the raw reading for the x,y, and z axis as well as the raw temperature reading. The values are not scaled according to the sensitivity or possible offsets.

(x, y, z, t) = QMC5883.read_scaled()

Return the scaled reading for the x,y, and z axis as well as the temperature reading. The x ,y and z readings are scaled to Gauss, the temperature to °C with compensated offset On QMC5883P temperature value is always zero.

QMC5883.set_sampling rate(sampling_rate)

Sets the sampling rate of the sensor. Accepted values are:

Value	Sampling rate
0	10 Hz
1	50 Hz
2	100 Hz
3	200 Hz

QMC5883.set_oversampling(oversampling)

Sets the oversampling factor of the sensor. Accepted values are:

Value	Oversampling
0	512
1	256
2	128
3	64

QMC5883.set_range(range)

Sets the magnetic field range of the sensor. Accepted values are:

Value	Range
0	2 Gauss
1	8 Gauss
1	12 Gauss (QMC5883P only)
1	30 Gauss (QMC5883P only)

QMC5883.reset()

Resets the device using the previously configured settings. This call is not required when settings are changed.

# Example for Pycom device.
# Connections:
# xxPy | QMC5883
# -----|-------
# P9   |  SDA
# P10  |  SCL
#
from machine import I2C
from QMC5883 import QMC5883P

i2c = I2C(0, I2C.MASTER)
qmc5883 = QMC5883P(i2c)

x, y, z, _ = qmc5883.read_scaled()