Does the CR300 support inverting logic levels on control port serial comms?
The CR300 control ports used for serial comms only supports inverted logic typical of RS-232. 1 = low, 0 = high.
It does not support TTL logic levels.
Is it possible for the CR300 OS to be upgraded to support TTL on Control ports and 300 baud on the RS232 port?
It is a hardware limitation. An OS upgrade can't change it.