DAQmxCfgDigEdgeStartTrig needs +5 V?

[anarkie]

Hello?

I posed some thread about DAQmxCfgDigEdgeStartTrig() and suspicious malfunction. But I found that PFI0 pin does produces +2.5 V, not +5 V. I wonder this low amplitude does not make DAQmxCfgDigEdgeStartTrig() activated. I have a TTL as an external trigger and want to receive this external trigger from PFI0.

But this code never works. DAQmxCfgDigEdgeStartTrig(taskHandle, "/Dev1/PFI0", DAQmx_Val_Rising);

So I checked the voltage pulse but the device is receiving +2.5V digital pulse from PFI0 pin. 

I wish to get a confirmation from NI Engineers whether DAQmxCfgDigEdgeStartTrig() needs digital pulses with +5V amplitude.

Because DAQ code works fine with +2.5V digital pulse in PFI0, I need to modify or just add voltage doubler if DAQmxCfgDigEdgeStartTrig() really needs +5V. 

Thanks,

[nayer]

Hello Anarkie,

I assume you are using E-Series board. The PFI lines on E Series are TTL compatible hence should be able to trigger to voltage greater than 2.4V, hence you do not need +5V inorder to trigger your acquisition. This more like the hardware property hence change in driver will not affect the operation of the card. What you can try is to increase the input signal to 3.3V and see if that works. 

Thanks

nAyer

[anarkie]

Thanks for reply. Currently it has +2.65V on PFI0 which is good for DAQ code. But DAQmx doesn't respond at all. I will try to increase it.