ALDL

[Steve=Ravet%Prj=Eng%PCPD=Hou at bangate.compaq.com]

sdbartho at cca.rockwell.com Wrote:
| 
| 
| 
| > A friend and I have been trying to come up with a way to 
| capture the data 
| > coming from the ALDL connector on GM cars.
| 
| What kind of GM car? Depending on the year, make, and model, the 
| data rate
| is quite different.
| 
| > We have the Diacom software from 
| > Rinda Technologies but we want something simpler. We have found 
| out how to 
| > trigger the data flow by bridging the A-B terminals with 
| different amounts of 
| > resistance.
| 
| Is this what the Diacom does? I thought they sent out the proper 
| ALDL mode
| request commands to get the ECM to send back the data it wanted. 

I don't think there is a way to send commands to the ECM on the ALDL system, 
since there is only one data line.  The ECM transmits it's info over the line, 
the dash listens in for some info it needs.  As far as I know the different 
resistances on the A-B line set the different modes.  This applies to the 
8192 baud stream in late model corvettes, others I don't know.

I have some info on the slow (150 baud?) stream used in older S-10s, 
Suburbans, etc. from Dan Furgason who is also on this list.  I can send it if 
anyone is interested.

As far as the 8192 stream goes, that is a topic that comes up here, on the 
hotrod list, and on the corvette list regularly, as far as I know no-one has 
decoded it themselves or pried the info out of GM.

Oh yeah, Ken Mosher on the GN/Ttype list has written a program that reads the 
ALDL info for that car.  It is the slow data stream, and so might work for 
other slow stream cars.

| 
| I'm working on a similar project for the '91-'93 Syclone/Typhoon, but I 
| haven't got it all working yet.

Is that an 8192 stream?

--steve

| 
| 
| Dig
| sdbartho at hwking.cca.rockwell.com
| 
|