[Gmecm] 8192 ALDL bit bang info?

[Jay Vessels]

Hi there!

http://www.techedge.com.au/vehicle/aldl8192/8192baud.htm

Has information on the 8192 bps interface.  Nothing odd here -- standard 
RS232 stuff.

> just presume that what I get back is valid and discard the checksum
> (in my first revision), but since I have to send a checksum with my
> messages and I can't exactly tell the ECM to also forget about that
> whole checksum thing, I guess I need to figure out how the checksums
> are calculated.  What should they look like?

Considering how electrically noisy an automotive environment is, I'd 
think the checksum going both ways is a good idea.

http://www.andywhittaker.com/ecu/aldl.htm

has information on the checksum, but it looks to be checksum  = 0xFF - 
(sum of bytes).  Stated another way, checksum + (sum of bytes) == 0.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)