USB-6212 Digital Output Ports Crosstalk

[SohaibAkhter]

Hi there,

I'm using a USB-6212 with my Windows XP Core 2 duo (32-bit) PC and the 32-bit Labview 2011. I'm trying to simulate pulse trains on each of the output lines of Digital ports 0,1, and 2, each at a different frequency. Port 0 is configured to give digital pulses of 4Hz, Port 1 is configured at 12Hz and the Port 2 is configured to give 32Hz pulses trough all its lines. The problem here is, all the port's outputs end up modulating one another, as in the output of Port 2 would show 32Hz pulses modulated on a 4Hz pulse. I assume it is some crosstalk between the digital channels. Has anyone else run into this problem? and have you got it fixed? let me know, thanks. 

Sincerely,

Sohaib Akhter

[RedAG]

The USB uses TTL for digital input/ouput and for TTL, all the receiver needs to know is just the High-to-Low and Low-to-HIgh transition. Anything above 2.7V is registered as a high and anything below 0.4V is low. A noise of upto 10-40mV is ok and can be expected in most cases.

[[dk]]

The reason you are seeing the ports modulate one another is because the USB-6212 only has two counters on board the device. So since you are trying to simulate pulse trains, which uses the on board clocks and counters, you are going to see some modulation between ports. 

[SohaibAkhter]

I'm not using the hardware timers, I'm using the 1kHz clock provided by Labview to generate my pulses

[SohaibAkhter]

Okay, so after doing a little more testing, the outputs of NI-DAQ are okay. The ports weren't giving crosstalk but they're connected across relays to circuits with the same power supply, such that if one input to the relay was high, it would permit the sourcing voltage to run through the first circuit even though the relay to the second circuit is pulsing but at a slower frequency, so when I connected the O-scope after the relay, it looked like there was crosstalk. Thanks everyone, and sorry for your time!