Re: LPC2138 timers

On Thu, 29 Jun 2006 17:27:53 +0200, Frank van Eijkelenburg wrote:

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
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.

From the data***:

* Four 32-bit capture channels per timer/counter that can take a
snapshot of the timer value when an input signal transitions. A
capture event may also optionally generate an interrupt.

If a snapshot of the timer is taken, doesn't the timer continue to run?
If it does, no need to reset the timer, just subtract the previous reading
from the current CAP reading using the same data width as the CAP register
for the math.


~Dave~
.