Have you actually simulated 3000 RPM at your desk, with the same duty
cycle/hysterisis as you have monitored on your Honda. I would suggest
that your real problem is with the interrupt on change.

Craig

Yes, of course! I wrote a programm which simulate the whole RPM-band of the
car. With the same style (around 2050 rpm: 9,9 ms high, 4,7 ms low)
It seems like the interrupt will be fired correct. I'm really confused about
the fact that the result is sometimes higher and sometimes lower than the
expected result.
When the Port-Change interrupt is the problem than i think the PRM must be
everytime to low. (the interrupt occures to late and the messured time is to
long)

Thanks for your idea.

Christian Dorner
aka Doc, ...

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