04-24-2015 09:29 AM
I have a PXI-6509 board in a PXIe-1073 chassis, with an RG1005050 cable. I'm using the DIO pins exclusively for digital output. I'm controlling the 6509 using DAQmx and MS Visual C++.
When I set certain bits high, I'm getting "glitches" or crosstalk with amplitude of 3-4 Volts and duration of 20-50 nanoseconds. The crosstalk is triggering my Device Under Test (DUT) and my measurement (oscilloscope) at undesired times. I'm wondering if there's a DAQmx setting to slow down the rise and fall times on digital outputs, and thus reduce the crosstalk.
Thanks for any help or suggestions!
04-24-2015 10:13 AM
Ribbon cable is horrible for noisy situations. But here are a couple of ideas to help:
1. Make sure all of the DIO are either set to be output and unused are set to 0 or make sure the unused DIO are inputs with the signal grounded on your test board.
2. Get a ferrite that is made to clamp onto a 50-pin ribbon cable. They are just iron cores that go around the cable, but they act as a kind of filter.
04-24-2015 10:27 AM
05-27-2015 09:23 AM
Thank you both for your suggestions. The ferrites didn't work, and a shielded cable wouldn't have been convenient, but you both got me thinking about the problem the right way. I ended up debouncing the signal in downstream firmware. I should have mentioned in my original post that firmware was available.
Kudos sent to both of you, and thanks again!