digital input filtering on a 6123 S-Series board?

[John@AEI]

Is anyone aware of a way to do digital input filtering on a 6123 S-Series board without adding external hardware?  I'm getting false triggers from noise.

[John_P1]

Hi John,

While the 6123 doesn't have built-in digital filtering like some of our other hardware, there are two methods that I can think of that you could use (other than external circuitry) to help avoid triggering off of noise.  This depends on how much noise you are seeing--I'll assume that you are only picking up extra triggers during transitions of your trigger signal.

1.  If you have an open analog input channel, you can configure an Analog trigger with hysteresis to avoid picking up duplicate edges.

2.  If you have an available counter, you could implement a retriggerable, single-pulse generation.  The pulse generation will not be re-armed until the previous generation has completed.  The pulse width should be slightly wider than the width of your external trigger to avoid picking up noise during the falling edge.

External hardware is not a bad idea either.  You would probably want to use a Schmitt Trigger.  You could use a voltage divider from the 5V rail to set your threshhold.

Best Regards,

[John@AEI]

Thanks for the feedback.  I like option #2.  I'll try something along those lines.  Thanks again.