The sam3 i2c code and the linux code use a 7-bit i2c address, while the avr, lpc176x, and samd21 i2c code uses an 8-bit address with the least significant bit always zero. A similar issue occurred in the host code (sx1509.py and replicape.py use 7-bit addresses while uc1701.py and mcp4451.py use 8-bit addresses). Consistently use 7-bit addresses in all the code. This breaks compatibility between host and mcu software, so make a change to the config_i2c command to force users to synchronize software updates. This also breaks common Smoothieboard configs, so update the mcp4451 code to validate the i2c_address. Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Welcome to the Klipper documentation. The overview document is a good starting point.