trigger off a analog edge to set a digital output

[thomasAnder]

I have multiple analog pulses and i want to set a digital output (port) off of each falling edge. I am using a PXIe-6363 with the analog signal connected to PFIO.  I cannot seem to get it to work...and suggestions would be appreciated.

[santo_13]

Please share the timing diagram of these signals to understand better. Are these digital port behavior known ahead of time? how soon must these react?

[Bob_Schor]

I don't know what you mean by the term "analog pulse" or "analog edge".  I'm not an electrical engineer, but I think it is fairly simple to create a little circuit  that will change an "analog signal" into a TTL "digital Pulse" that outputs either +5 V ("High", or "1") or 0 V ("Low", or "0) (I don't remember, or possibly never worried about, precisely the voltages at which the switching occurs).  The point is, if your (analog) input signal varies from 0 to +5 volts, is "relatively noise free", and can drive a TTL input (which I don't think takes much current), it should work.

Bob Schor

[thomasAnder]

The analog pulse width is 10ms +8V, the re-occurs at ~40Hz. The digital port needs to be set during the time from the falling edge to the rising edge of the next pulse. 

The analog pulse is created by the AO on the PXIe-6363 card, I jumped AO to PFIO to have the external edge for the Digital port on the PXIe-6363 to use.

The vi's I am using are attached, top level is Voltage waveform with dig edge.

thank you for your help

[thomasAnder]

AO is jumpered to APFIO

[Kevin_Price]

Honestly, I would approach this differently from the start.

Since the analog pulse you're trying to react to is an AO task & waveform that you define and control, I would define and control a corresponding DO task & waveform, then properly sync it to AO.

A straightforward approach is to configure the DO task to use the AO task's sample clock for its timing, define the proper digital output state at each sample point, and then call DAQmx Start for the DO task *before* calling it for AO.

There's really no need to rely on triggering schemes here when you're the one controlling when the AO falling / rising edge samples are going to happen.

-Kevin P

[thomasAnder]

Thank you very much for your insight.

Not sure how to do what you recommend. The AO uses the created analog waveform for timing, I need the DO to set state right after each falling edge of AO.