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Gets the period of a capture channel.
The integer number of counts in the most recent full cycle on the capture channel input, or 0 if there has been no transition on the input since the last time the period was read.
The capture channel must be assigned a pin using the pin property before the period function can return a valid value.
The value is in counts; use the resolution constant to get the number of counts per second. The actual frequency can be computed as follows:
freq = Cell.Capture.resolution / Cell.Capture.period(channel);
while the actual period (in fractional seconds) can computed as follows:
period = Cell.Capture.period(channel) / Cell.Capture.resolution;
where channel is the desired capture channel number.
Once the period has been read, subsequent attempts to read the value will return 0 until a transition (low-to-high or high-to-low) occurs on the channel's input pin.
See example for the pulseHi function.