ALDL info

[Todd King]

  <<<
  Hey Todd,
       I'm not so sure about that, my reasoning is that I have a parallel to
  serial converter which can transmitt at 110, 150, 300, 1200, 2400, 4800,
                 Mark Glicksman
  >>>
  
  Not too sure about what? I'm not worrying really about the baud rate 
  "problem", I'm saying that the GM ALDL data stream is pulsewidth modulated. 
  The baud rate mismatch doesn't really apply here since to read the stream as 
  RS 232 is the "wrong" approach anyway! The PWM technique offers tremendous 
  noise immunity over voltage level encoding and is why it was chosen. BTW once 
  you build your PWM demodulator (be it a SW or HW solution; either way it's 
  really easy...) and start reading data you'll find that some of the data 
  fields and locations in the stream are similar (like rpm, etc) between the 
  various cars. You can probably reverse engineer most of 'em, especially now 
  that Mr Ravet has kindly provided the bit-level protocol...
  
  Todd