[b3lha]

I got the ASCII mode working !!!!!

As Calum pointed out there is a flag in ROM at 8029 that determines whether the ECU starts up in binary or ASCII mode. This flag gets copied to RAM at 12CF.

If the flag is 0, the ECU will run in binary mode. If it is 1, ASCII mode.

The subroutine at C005 switches the flag to 1, but I don't know what set of circumstances will make the ECU call this subroutine. Maybe it's some sort of test mode?

Anyway, the simple solution is to set the flag manually.

Set the laptop to 1953 8E1 as normal. Send 7812CF00 to read location 12CF. Should get 12CF00 back repeatedly. Then send AA12CF01 to write 01 into location 12CF. The output stops immediately because the ECU comms parameters have changed.

Then set the laptop to 4808 8N1 and send 7F313233343030 to read location 1234. You should get back 3132333430300a0d which is ASCII for 123400 + line feed + carriage return. It does not repeat like the binary mode.

I'll have to do some tests and see how the speed compares to binary mode. I don't see it being very much faster because it's sending more data. But it's nice to see it working.