Re: LPC2138 timers

"Frank van Eijkelenburg" <someone@xxxxxxxxxxxxxxxx> wrote in message
news:482ef$44a3f118$3e3aa7a5$13428@xxxxxxxxxxxxxxxxxxxx
I am using a capture pin in combination with a timer of the LPC2138
controller.
Each time a rising/falling edge is detected the running timer value is
captured
and stored in a CAP register. I am using this method to measure timing
between
the edges and calculate the frequency of the signal (squarewave).

Each time I enter my interrupt service routine I reset the timer (to start
a new
measurement). Is there a way to do this automatically, because now I have
a

Surely that will introduce a error due to the interrupt latency. Shouldn't
you be subtracting the previous capture value leaving the time to free run?

small gap between the edge and the start point of measurement. I saw that
you
can automatically reset the timer if a match value is reached, but could
not
find this possibility for the capture pins.

You shouldn't need to reset the timer at all. You want it to keep going so
that the results are entiely based on hardware timing without and latency
issues (except to respond to the interrupt before the next capture is
expected).

Peter


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