Hi JMBacker,
You can make a frequency measurement from
you digital lines, but you would have to do it in software. To actually
take a frequency measurement in hardware you would have to use a
counter input.
In order to do this with your digital
inputs you will have to know your sampling rate, and do some
manipulation to the array of values that you get when reading the
values from the port. You would only be concerned with the 4 lines of
the port you configure. Once you store that data in the array you would
have to check for the number of samples between two transitions from 0
to 1, then multiply that by (1/sampling frequency) and take the inverse
of that value. This will give you the frequency value of one period of
your input signal. You would have to do this process with each of the 4
desired input lines in one port.
Attatched is an
example program that takes that measurement and computes the frequency
in software. This is in LabVIEW version 8.2.1, but can be used in any
version at or newer than that version.
Chris N White
High Speed Products Group
