Generating TTL Signal in LabVIEW

[yezdi777]

Hello, 

I am trying to generate a 0-5V TTL pulse from my PCIe-6343. For this, I am using a digital line and the following program. Although I can vary the frequency of the signal with my wait milliseconds loop (right now it's 10 ms), I am not able to understand why my voltage is switching between 0-2.5V. I use a scope to measure this. Is there a way that I can have it offset so I generate a 0-5V signal? Or do I need to use counters to do this? 

Thanks in advance,
Rahul

[Kevin_Price · Accepted solution]

Sounds like your output is connected to something with a (relatively) low impedance.  Remember, V=IR.  Your DAQ device will have current sourcing specs you can look up, and your external connection likely has a low enough impedance that ~2.5V is the product of the the max sourcing current and the external impedance.

It's possible the current sourcing capabilities will vary among the DIO ports, some of which do double duty as possible output pins for counter tasks.  But in the end, this is a hardware issue that might not be solvable via software.

-Kevin P

[yezdi777]

Thanks for the insight Kevin. I will double check the impedances!