PIC16F688
EasyPIC4 w/ PIC16F688 at 12MHz withrigged connection from hardware UART to on-board level shifter.
After some jiggery to get the PIC16F688 sample I received today talking to the built-in level shifter on the EasyPIC4 I had no problem getting the basic software for the HMLiberator running and responding to commands. It’s currently running at 12MHz, but as soon as I get some 20MHz crystals it’ll run there. This will give a baud rate just about 0.16% skewed from the specified 9600 baud rate, and I think that’s close enough.
I still have one problem to sort out before I try plugging it into the car, and that’s with the receive FIFO. With it set at the default of 40 bytes I can get five commands sent and responded to, and then the sixth just fails. As I was testing with a seven-byte command (and 7×5 = 35, just below 40), I think I’m hitting point where the FIFO wraps around (or something — I don’t understand it well enough yet). The incoming commands are of varying size, so I’m not really sure how to work around this yet.
At least I know where the problem lies. Once that is sorted (or whatever) I’ll plug the thing into the car and see what it does. If that goes well, which I expect it will after some basic software changes, I’ll finish up the v1.0 circuit / board design and order a run of boards and make up a first batch of five or so.