Sharing an external sample clock between PCI-6722 and PCI-6602

[shokey]

    I need PCI-6602 work with PCI-6722。6602 shares 6722’s ao/SampleClock as external clock and triggered by 6722’s ao/StartTrigger。The master device is 6722, which refered as Dev1, and the slave device is 6602, which refered as Dev2. A RTSI line is used to connect the two devices correctly.

    I use C API to finish my program and my code is as follows:
 
//config 6722 analog out task
1、DAQmxCreateTask("NI6672", &hAOTask);
2、DAQmxCreateAOVoltageChan(hAOTask, "Dev1/ao0", "", -10.0, 10.0, DAQmx_Val_Volts, "" );
3、DAQmxCfgSampClkTiming(hAOTask, "", 1000.0, DAQmx_Val_Rising, DAQmx_Val_ContSamps, 1000);
4、DAQmxWriteAnalogF64(hAOTask, 1000, 0, 10.0, DAQmx_Val_GroupByChannel, data, NULL, NULL);

//config 6602 counter task
5、DAQmxCreateTask("NI6602", &hCounterTask);
6、DAQmxCreateCICountEdgesChan(hCounterTask, "Dev2/ctr0", "", DAQmx_Val_Rising, 0, DAQmx_Val_CountUp);

//use /Dev1/ao/SampleClock for external clock
7、DAQmxCfgSampClkTiming(hCounterTask, "/Dev1/ao/SampleClock", 1000.0, DAQmx_Val_Rising, DAQmx_Val_ContSamps, 1000);

//use /Dev1/ao/StartTrigger
8、DAQmxSetTrigAttribute (hCounterTask, DAQmx_ArmStartTrig_Type, DAQmx_Val_DigEdge);
9、DAQmxSetTrigAttribute (hCounterTask, DAQmx_DigEdge_ArmStartTrig_Src, "/Dev1/ao/StartTrigger");
10、DAQmxSetTrigAttribute (hCounterTask, DAQmx_DigEdge_ArmStartTrig_Edge, DAQmx_Val_Rising);

//start counter task first
11、DAQmxStartTask(hCounterTask);

//start 6722 task
12、DAQmxStartTask(hAOTask);

I run it on the MAX virtual Device, and the Step 11always returned -89120。

I try to slove this problem, so I change the Step 7, use /Dev2/PFI9 to instead of /Dev1/ao/SampleClock.

7、DAQmxCfgSampClkTiming(hCounterTask, "/Dev2/PFI9", 1000.0, DAQmx_Val_Rising, DAQmx_Val_ContSamps, 1000);

The code runs well, but I don’t know which terminal is connected by /Dev2/PFI9. Does it connect to /Dev1/ao/SampleClock？

I use another API DAQmxConnectTerms to ensure that, I add a Step before Step 11.

DAQmxConnectTerms( "/Dev1/ao/SampleClock", "/Dev2/PFI9", DAQmx_Val_DoNotInvertPolarity );

The program also run well. But I am still not sure that 6602 is sharing /Dev1/ao/SampleClock。If not, which terminal of Dev1 is connected by /Dev2/PFI9?

Is my code right? If not, hwo to fix my code or supply some example for me? Thanks.

[Jim_S]

Hello Shokey,

From looking over your post, it looks like you want to program in C, using simulated instruments, a master/slave design with a PCI-6602 and PCI-6722. The PCI-6722 is the master device and the PCI-6602 is the slave device. In order to implement this with the real cards, you would need a RTSI cable between the 2 cards in order to pass the triggers and the sample clock. Unfortunately with simulated devices you can't implement this so parts of your code won't be able to work exactly like if you had the instrument.

If you did have the instrument, you can implement this by performing the following steps:

Master Device:

1.) Export the ao/SampleClock and ao/StartTrigger to a RTSI Line. (See DAQmx C Reference help for DAQmxExportSignal to export these)

Slave Device:

1.) Set the Sample clock and the trigger to the RTSI.

There is another forum that I think will help you out to implement this correctly. In this forum, the customer was trying to export a trigger through a RTSI and the problem he was experiencing was a broken RTSI cable. His code, he states, works. I hope this helps you with this and if you have any more questions, feel free to post.