Start with 0xff instead of 0x00, so the CRC will be nonzero (and length
dependent) for data that is all zeroes.
Remove unnecessary masking, since `crc` is already an 8-bit integer.
I2C register layout changed a bit to make various operations easier
to implement in FW and for the user.
Flashing/debugging tools now share more code. Firmware is now more
configurable (it's now possible to compile-out various features).
Self-testing for column-shorts is implemented.
Firmware is optimized for low power consumption.
