How can I start simulataneously two GPCTR counters on a PCI-MIO16E?

[DITA]

My system is a PCI-MIO-16E4 which I'm programing with Visual Basic CW components.
I use the GPCTR1 to trigger an event and my acquisition is triggered by GPCTR0 at a frequency which is double that of GPCTR1. However, I observe a shift in the acquisitions because both counters are not synchronized. How can I start the two counters simultaneously?

[John N]

Hi Mario,

The way to trigger the counters together is to use a gate triggered start. I am including an example that works for single pulse generation on an E-series board. The first vi to open is the Delayed Pulse-Int(DAQ-STC)0.vi.

The idea is just that you wire one trigger line to the gate of both counters, and when you are ready to generate the counter signals, you will provide an edge on the trigger line.

If you are using Generate Pulse Train.vi, the difference from the example for your program will be to add the gate mode input to Generate Pulse Train.vi instead of Pulse Config.vi

If you want to reply, I'd be happy to hear how this works for you.

Regards,

John N.
Applications Engineer
National Instruments

[DITA]

Thank you for your quick reply, I will try it asap. However, I am using Visual Basic CW tools, so I can't use the examples you attached. I would had a comment/question regarding the gates sources: it is not clear to me how they are numbered. For example if I choose an hardware digital trigger, which source number corresponds to PFI0/TRIG1?
Best regards,
Mario

[John N]

Hi Mario, I tried replying to your comment immediately after I saw it. I must have done something wrong since it didn't post. I apologize.

Basically my response is that only the NI-TIO boards such as the NI-6533 and NI-6534 (boards with our specialized timing chip) are able to directly trigger the beginning of counter acquisition. If you want to do it with MIO boards then you can use the gate signal to enable both counters at the same time. To do that in ComponentWorks, you can just choose the same source for both counters.

The MIO solution still will not synchronize the beginning of the pulses but will make sure they start within one of the longer pulses of each other.

If you want to guarantee the counter-pulse generation synchronization, t
hen you can get an NI-6601 counter/timer board that has counter/pulse synchronization as a feature.

For your question about choosing the hardware digital trigger, you can actually use "PFI0" since you are using an MIO board. You can read about this in...
StartMenu->Programs->National Instruments->Measurement Studio->Help->MeasurementStudioReference.
Within that help file, you can read about "StartCondition" and it will tell you about the options and what the different source values indicate.

I hope this is helpful.

Sincerely,
John N
Applications Engineer
National Instruments

[John N]

Hi Mario. This is John again. I looked into doing the same thing in ComponentWorks (sorry I missed that before).

I have very quickly written an example that has the effect of synchronizing the counters.

Please be aware that unless you buy a NI device with hardware timing triggering (NI-TIO based devices) then you can't directly trigger counters or timers. Here is a web page that compares the timing chips on our different devices: Timing Chips on National Instruments Devices

What the example does is setup both counters for continuous pulse generation. However the gate is set for low signal gating on PFI0. The trick i
s to keep PFI0 (or whatever trigger you choose to use) high until you are ready to run the pulses. The CWPulse.configure and CWPulse.start enable the counters, but the counters wait for the gate before producing pulses.

The difference between this and real triggering is that here you will need to keep the PFI0 pin pulled low for the amount of time you want to produce the pulses. Also, there is a chance that these pulses will begin with one timer width difference (due to the non-timed and independent detection of the gate level by the counters).

[John N]

Hi Mario. This is John again. I looked into doing the same thing in ComponentWorks (sorry I missed that before).

I have very quickly written an example that has the effect of synchronizing the counters.

Please be aware that unless you use a NI device with hardware triggering for timers (NI-TIO based devices) then you can't directly trigger counters or timers. Here is a web page that compares the timing chips on our different devices: Timing Chips on National Instruments Devices

What the example does is setup both counters for continuous pulse generation. However the gates are set for low signal gating on PFI0. The t
rick is to keep PFI0 (or whatever trigger you choose to use) high until you are ready to run the pulses. The CWPulse.configure and CWPulse.start enable the counters, but the counters wait for the gate before producing pulses.

The difference between this and real triggering is that here you will need to keep the PFI0 pin pulled low for the amount of time you want to produce the pulses. Also, there is a chance that these pulses will begin with one timer width difference (due to the non-timed and independent detection of the gate level by the counters).