Newbie ALDL question

[Roger Heflin]

On Mon, 1 Mar 1999, Barry Tisdale wrote:

> Bill -
> 
> Managed to get the ALDL interface working quite well - are you still interested in this project?  I'm using a QuickBasic program to read the data - had no luck w/ GCAR.  BTW, in your last letter, you referenced using "4 diodes" in the MAX232 circuit - should those be transistors (2N3904)?  I used a MAX233 chip - no external caps; '04 inverter not needed.
> 
> Get *lots* of data out, now just have to correlate it w/ what my scan tool reads.
> 
> Any collaboration gladly accepted!
> 
> Barry
> 
I don't know about the syclone, but something useful, diacom appears
to store the data stream exactly as it comes of the interface in their
data files.    I have a ALDL spec for my car, and using that spec I
was able to get meaningful data out of the diacom data file.   Also,
there will be two bytes at the front of each data stream, that will be
the prom id, it will be repeated at the beginning of each set of data,
then there are typically several bytes of data that are error flags
(trouble codes, usually all zeros if everything is good).

There should be a spec for the syclone, someone did send me a spec for
my car (93 Z28), and it does seem to be correct, because I have been
able to decode meaningful data from the diacom data files (things that
weren't displayed, or not displayed accurate enough).

					Roger