v0.018
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second prototype

major fixes:
- add bus switch instead of common power rail for pull-up resistors
- replace MAX232 RS-232 transceiver with 3.3V capable and enable pin alternative
- add diodes on xV voltage regulator output to prevent voltage regulator to sink current
- add transistor to disable completely 12V voltages regulator, allowing it to got to 0V instead of 5V)

v0.001
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first prototype