OBD II download

[Tom Hussey]

Hi,

It's been a while because I spent last weekend at the race track but I
think I have finally figured out OBDII download. The way it works is...

The ecm is placed in download mode with a frame that is set for physical
addressing (bit 2 of the header is set). Target is $18 and secondary ID
is $34. The rest of the frame is length and address info. Interesting
that the code allows for 24bit addressing. The following frames are data
frames till the byte count is done.

My next goal is to prototype the interface. I will be using Harris chips
(cause I got em free). Once it is working I will give a better
description of the whole thing. If anyone is interested in building an
interface or working along on this, drop me a line.

-Tom