ALDL summary and thanks for participation

[george dailey]

Gentlemen we have come full circle on this. Help me out (as I'm sure you
will), the facts are:

There are some hardware goodies in the Diacom software cable.  The goodies
may have been placed there as a marketing  protection device. Think about
it. Diacom sends signal to goodies,  goodies respond back to Diacom,  Diacom
will now start reading the ecm data.  This kills software pirating.  Or they
may be legitimate hardware interfaces.  I'd like to know what our expert
readers have to say.

The pre P4 ecms will transmit on demand at 160 baud.
"The ALDL for my (Dan Fugerson) 89 Suburban is a continuous 160 bit/sec bit
stream.
It begins with a sync character of 9 consecutive "1" s.Each subsequent byte
begins with a "0" and then the 8 data bits. The stream continues until all
data is read. Another sync character is sent and the stream repeats with
updated values."

The P4 and later ecms have to RECEIVE a pass data stream before they will
transmit at one of two predictable baud rates.  160 or 8192. "The data is
not in ASCII, but regular 8-bit (mostly) unsigned integers.  There are some
16-bit values that come out.", Scot Sealander.  Scott, I plan to RTM,  in
the mean time, can you feed us folks in hacker land a few more tidbits of
information that you think would help a hacker.

If the data string is unsigned integers for new or old ecms, the hacker
would have to convert each  integer to it's real number equivalent.  Some of
the data is in the form of  "A/C    yes"  Once you got the real numbers you
must decide which physical parameter it stood for.  Time consuming but not
impossible.

OBD-II standards:  I'm sure this is an excellent standard but,  I know
nothing about it. ouch!

Bottom line-- I've got a complete  350 '89 TPI harness on my living room
floor.  If  I can get some code to read the raw data, I'll tinker with
converting it into usable data.  As soon as the weather breaks, I will put
the whole TPI setup in Maxine (my chopped and dropped '58 Chevy truck) and
cruise for women!

Thanks to all who have given input.

George M. Dailey  gmd at tecinfo