Hi John,

Perhaps instead of getting the signal at the ECU, and possibly causing
problems by drawing too much current, you could source the signal at the
diagnostic connector in the engine bay. Not sure of the pinouts of the
connector but I'm sure that someone at http://forums.skylinesdownunder.co.nz
or somewhere like that knows.

The diagnostic connected is specifically designed to allow other devices to
be connected without killing the signal to the ECU.

On my car for example, there is an "IG" pin (ignition) which is similar in
terms of output to what you are describing. I use it to get the engine RPM,
there are also pins for road speed, and individual wheel speeds (from all 4
wheels) from the ABS sensors... Very handy!

> -----Original Message-----
> From: Hulatt, Jon [SMTP:jhulatt@MONSTEREUROPE.COM]
> Sent: Wednesday, September 24, 2003 12:15 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [EE:] (automotive) frequency trigger
>
> Secondly, is the question of how to interface the 12v square signal with
> the
> pic? I'd thought of using an optoisolator, but is there a better, or
> simpler
> way of protecting the pic from a) getting 12v not 5v and b) any dirty
> spike
> type things? I think I need a relatvely high impedance, because the signal
> goes into the ECU, so if I steal too much of it, I may make the car rather
> ill.
>
> Appreciate your thoughts.
>
> Jon
>
>

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