• Suported magnetometers HMC5883L(mag), BNO055 (9dof IMU), BNO085 (fused absolute rotation quaternion)
• The original bosch sensortec driver for bno055 is used as is (under imu/bno055 folder)
• The original ceva hillcrest labs driver for bno085 is used as is (under imu/sh2 folder)
• bno055.h and bno085.h headers under the root folder are just wrapers over the original bno055/085 drivers with pico specific i2c read/write HAL callbacks.
• HMC5883L uses NED reference frame (x is the yaw/heading vector) while bno055/085 deafult is ENU (y is the yaw/heading vector)
• Clone this repository at the same level as other examples under the pico-examples directory.
• Edit the root CMakeLists.txt of the pico-examples repository and include this repository in the build using add_subdirectory(hmc5883l).
• Build the examples as usual using 'cmake --build ..'
• Calibrate the magnetometer first using the calibrate function.
• Copy the resulting UF2 file (main.uf2) onto the Pico and use PuTTY to check the heading values.
• Reported heading can be cross-verified using a floating magnetized needle or something equivalent.
• The heading should vary from 0 degrees (true geographic north) all the way to 360 degrees (one full x-y plane rotation), and then wrap back to 0.
• all mag/imu headings are pointing to magnetic north. As such, local declination needs to be accounted for.
• The app directory has a c++ proxy app that reads messages off pico's COM port (usb) connection and publishes them over a websocket server
• App directory also has a three.js visualizer that maintains a websocket connection to the c++ proxy app.
• The axis helper gets rotate around the z axis based on the yaw reported by the IMU over USB/UART.
• There's some issue on windows with reading the com port directly using the proxy app.. just start putty first, close it and then launch the proxy app.

c++ proxy app

vcpkg install websocketpp
cmake -DCMAKE_TOOLCHAIN_FILE=D:/vcpkg/scripts/buildsystems/vcpkg.cmake ..
cmake --build . --config Debug
app.exe \\.\COM4

three.js visualizer

npm install http-server -g
http-server -p 1234 --cors
launch the visualizer url http://localhost:1234/