http://bitchin100.com/wiki/index.php?title=BCR_TTL_SERIAL_HACK
I've documented the information around using the BCR port as a half duplex TTL serial port. The solution for M100 is to solder in a single wire on the backside of the PCB. I expect a similar solution exists for T102 and other machines. I've included the schematic and layout change as well as my code for demonstrating M100 <--> M100 transmission at 57600 using BCR port. Also, my code for very fast 115600 and 128000 baud transmission is there for reference. Steve
