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Re: Strange ALDL Blather
>Thanks Scott, but what does that mean?
Remember this is "the chatter", and won't tell you much. The meat is when
you request data from the ECM. My chatter from my LT1 Z28 looks like this:
F0 56 F4 C6
90 5A 25 00 40 5C FF 56
0A 58 95 03 A5 61
90 5A 26 00 40 5C FF 55
You can pick apart packets from a datastream by looking for patterns and
then calculating the checksum. Use Win 95 Calculator, set to Hex and Byte
mode. Add all digits, hit NOT, add 1. There's the checksum.
Above, the 25 and 26 are RPM*25 values (925 and 950 RPM respectively), and
the 40 is intake air temperature.
When you send it a "shut up" command of F4 56 08 AE you can follow it up
with a Mode Request, and that should start spitting real data at you. There
are quite a few modes, they follow the format F4 57 01 XX CS, where XX is 00
thru ??, and CS is checksum.
I suggest using a spreadsheet to look for trends in the data, unless you can
find a protocol description lurking about.
Good luck,
Andrew
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