Hi,
I have a question about receiving a TTL pulse from an external input and I want to implement it in Python. Once I receive the TTL pulse, I will use it to trigger my code. Could you please give some suggestions where to start? Do I need to do the push-pull connection to initialize the digital input pin to low? How to continuously read this pulse? Thanks in advance!
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There are two options depending on pulse width. In both cases you connect your TTL pulse signal to a digital I/O, and in a loop poll the U3 to detect the pulse.
Option 1: If your pulse width 10 ms or greater, you can just read the digital I/O state in a loop and detect the change in states. When you detect the change from low to high, and then back to low, a pulse occurred. The quickstart demonstrates reading from a digital I/O.
https://labjack.com/support/software/examples/ud/labjackpython/low-level
Option 2: Configure and use a counter on a digital I/O line. Read the counter value in a loop with the reset option. When the counter value is >= 1, a pulse or multiple pulses were detected. Counts occur on falling edges. Here some example code here on configuring (configIO) and reading from the counter (getFeedback with u3.Counter):
https://labjack.com/support/datasheets/u3/low-level-function-reference/f...
Configure once before your poll loop and then use the getFeedback call in your loop to read the counter value.
I appreciate your immediate response, and the 2nd option worked for me because the pulse width is about 0.2 ms. Thanks!