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This year, our team (alpine robotics) used the HC11 in a custom circuit designed to monitor the position of the translational drive wheels. We did our communication to the RC through the programming port, and the interfacing was relatively straightforward.
To correct the echo byte, we just programmed the HC11 to discard the first input that it recieved after sending the output, and we had no problems. Our biggest problem was that the RC is slow, so that the RC would not be able to receive data in time. This was fixed with a delay in the HC11 program.
We also had other minor problems due to wiring. Once we forgot to cross pins two and three, which are transmit and recieve. When the custom board is connected to a serial port of a computer, these pins are crossed inside the computer's wiring, but when the custom circuit is connected to the RC, you must cross them yourself. Also, for some reason that I forget at the moment, we had to connect pin 4 to ground as well as 5.
I still have all our resources, including the PCB schematic, the assembly program, and I think our PBASIC program is on the white pages. Contact me if you want any of those things.
-Bobby Sakurai
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