Raspberry Pi Pico W with CMPS12 compass

Example code of connecting the Raspberry Pi Pico W to a CMPS12 digital compass.

Connections

Description	Colour	Pico W	CMPS12 compass
Power 3v	Orange	pin36 3V3(OUT)	3.3v
Ground	Black	pin3 GND	GND
i2c Data	White	pin1 GP0 i2c0 SDA	Second from top
i2c Clock	Blue	pin2 GP1 i2c0 SCL	Third from top

Photo

Sketch

	# Raspberry Pi Pico W - CMPS12 digital compass
	# Copyright (C) 2023 https://www.roboticboat.uk
	# e156e28e-ce3e-49e8-9e22-5b7a61f62125
	#
	# This program is free software: you can redistribute it and/or modify
	# it under the terms of the GNU General Public License as published by
	# the Free Software Foundation, either version 3 of the License, or
	# (at your option) any later version.
	#
	# This program is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.
	#
	# You should have received a copy of the GNU General Public License
	# along with this program. If not, see <https://www.gnu.org/licenses/>.
	# These Terms shall be governed and construed in accordance with the laws of
	# England and Wales, without regard to its conflict of law provisions.
	#
	# User Interface https://thonny.org/
	#

	# Register Function
	# 0 Command register (write) / Software version (read)

	# 1 Compass Bearing as a byte, i.e. 0-255 for a full circle
	# 2,3 Compass Bearing as a word, i.e. 0-3599 for a full circle, representing 0-359.9 degrees. Register 2 being the high byte

	# 4 Pitch angle - signed byte giving angle in degrees from the horizontal plane, Kalman filtered with Gyro
	# 5 Roll angle - signed byte giving angle in degrees from the horizontal plane, Kalman filtered with Gyro

	# 6,7 Magnetometer X axis raw output, 16 bit signed integer with register 6 being the upper 8 bits
	# 8,9 Magnetometer Y axis raw output, 16 bit signed integer with register 8 being the upper 8 bits
	# 10,11 Magnetometer Z axis raw output, 16 bit signed integer with register 10 being the upper 8 bits

	# 12,13 Accelerometer X axis raw output, 16 bit signed integer with register 12 being the upper 8 bits
	# 14,15 Accelerometer Y axis raw output, 16 bit signed integer with register 14 being the upper 8 bits
	# 16,17 Accelerometer Z axis raw output, 16 bit signed integer with register 16 being the upper 8 bits

	# 18,19 Gyro X axis raw output, 16 bit signed integer with register 18 being the upper 8 bits
	# 20,21 Gyro Y axis raw output, 16 bit signed integer with register 20 being the upper 8 bits
	# 22,23 Gyro Z axis raw output, 16 bit signed integer with register 22 being the upper 8 bits

	import machine
	import time
	from micropython import const

	# CMPS12 compass registers
	i2cAddress = const(0x60)

	CONTROL_REGISTER = const(0)

	BEARING_REGISTER = const(2)
	PITCH_REGISTER = const(4)
	ROLL_REGISTER = const(5)

	MAGNET_X_REGISTER = const(6)
	MAGNET_Y_REGISTER = const(8)
	MAGNET_Z_REGISTER = const(10)

	ACCEL_X_REGISTER = const(12)
	ACCEL_Y_REGISTER = const(14)
	ACCEL_Z_REGISTER = const(16)

	GYRO_X_REGISTER = const(18)
	GYRO_Y_REGISTER = const(20)
	GYRO_Z_REGISTER = const(22)


	# i2c data
	i2cdata = machine.Pin(0)

	# i2c clock
	i2cclock = machine.Pin(1)

	# Start the i2c network
	i2c = machine.I2C(0, sda=i2cdata, scl=i2cclock, freq=100000)

	# Function for reading bytes from i2c module registers
	def i2cRead(registerAddress, numBytes=1):

	# b'\rf' would indicate an error
	return i2c.readfrom_mem(i2cAddress, registerAddress, numBytes)

	# CTRL + C to stop the program running.
	# Without the try: except it is very hard to stop the infinite loop
	try:

	# Infinite loop, like on the Arduino
	while (True):

	# Capture any i2c network errors
	try:

	# Receive 4 bytes
	# We start at the BEARING_REGISTER but each adjacent byte
	# will return the contents of the PITCH_REGISTER and ROLL_REGISTER
	receivedBytes = i2cRead(BEARING_REGISTER, 4)

	except Exception as e:
	# Update the User
	# b'\r\xc0' would be an error
	print(e)
	print(hex(receivedBytes[0]))
	print(hex(receivedBytes[1]))
	print(hex(receivedBytes[2]))
	print(hex(receivedBytes[3]))
	continue

	# Calculate full bearing (float)
	# Shift the byteHigh bits to the left. Multiply by 2^8
	bearing = ((receivedBytes[0]<<8) + receivedBytes[1]) / 10;

	# Compass pitch - byte [0 to 255]
	pitch = receivedBytes[2]

	# Need to convert unsigned byte into signed
	if pitch > 127:
	pitch -= 256

	# Compass roll - byte [0 to 255]
	roll = receivedBytes[3]

	# Need to convert unsigned byte into signed
	if roll > 127:
	roll -= 256

	# Update the User
	print("Bearing",bearing, "Pitch", pitch, "Roll", roll)

	# Need some delay else the print overruns Thonny screen updates
	time.sleep(0.1);


	# Interrupt handing
	# Capture the CTRL + C event
	except (KeyboardInterrupt, SystemExit):

	# Update the user
	print ("Well done. Finished\n");

view raw picoW_CMPS12.py hosted with ❤ by GitHub