ALDL

[TBK]

-----Original Message-----
From: frederic.breitwieser <frederic.breitwieser at xephic.dynip.com>
To: andy quaas <diy_efi at efi332.eng.ohio-state.edu>
Date: Monday, June 29, 1998 8:43 AM
Subject: RE: ALDL


>Does anybody know how diacom talks to the parallel port on a PC for
>ALDL monitoring?


>1980's GM ALDL 160 baud:
>The data is spewwed out of the ECM with different length pulse widths, and
the
>diacom software, through the parallel port, monitors the pulse width, then
>determines the value, assembling the data in your PC so it can display the
i>nformation on the screen.  A simple, software UART at its finest.


Actually the timing is fixed. There is a start bit and a fixed window for
valid data.

Diacom uses a printer line to simulate a serial port.

Various other lines are used to control the ALDL mode.

It's pretty clever.

TK