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>
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