How to generate synchronously digital pulses with analog waveform generation?

[Alexej_P]

I generate sinusoidal waveform (from 1 to 20 periods at once) using the analog output AI0, from 50 up to 10 000 Hz. I need to generate synchronously TTL pulses at a certain phase for a small fraction of the period (usually 1%). The easiest way is to generate that pulse on the analog output AI1. I did so – it works fine.

The problem is that the PCI-6115 card can output only 5 mA on AO and the external device (image intensifier) needs up to 24 mA.

One solution is to use digital output. The question is how to synchronize it with the analog output? Is there a way to continuously generate pulses using DO triggered by an external source – AO1 in my case? Are any other ways  to do it?

I am using the PCI 6115 card, LabView 2011.

[adamcseh · Accepted solution]

Dear Alexei_P,

of course it is possible to synchronize and custom trigger the digital outputs of NI DAQ devices. However, we have to differentiate between triggering and sample synchonization. While trigerring means just starting a certain task when a condition occurs (trigger condition) the latter one means synchronously performing tasks to a common source.

As far as I was able to understand it from your description you would like to start the AO and DO tasks at the same time and share the sample clocks between them to achieve synchronuous operation. One way to do it is configuring the AO sample clock to be the sample clock of the DO task. Please see the attached code for an example.

You can also find some addition useful information about timing and synchronization of DAQ devices here:

http://www.ni.com/white-paper/4322/en

Hope this helps you.

Best Regards,

[Alexej_P]

Dear adamcseh,

thank you for replying soon. I did as you suggested, plus used ai/starttrigger to start at the same time AI, AO and DO. The program runs with no errors, but it seems there is no access to DO on my BNC2111 (I tried port0/line0 and looked at all six PFI connectors) or I am doing something wrong. I will try tomorrow another connector block - CB-68LP, where there is access to all pins

[Alexej_P]

Dear adamcseh,

today have I tried the program with CB-68LP connector block to see DO - everything worked just fine. Thank you!