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Add debug to usart_rx
Add simple command history, recall with TAB
Add quarter-dB precision to master volume, adds floating point
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Add error checking to iic commands
Slave boards: Add chip as function parameter
Move cs3318 functions to its own file
add get_preferences function, remove extern
add float to sscanf, use float for volume instead of two ints
add get_twi_master function, remove extern
add get_debuglevel function, remove extern
add set_taskflag function, remove extern