Multi-device synchronization

[lnc]

Hello,

I need to synchronize the data acquisition using 2 PCI 6143 cards, ie. the data acquisition has to start at the same time for the 2 cards.  Has anyone done this synchronization before using CVI?  Will appreciate your help.  Thank you.

[Graziano]

Hi!

   2 solutions, in my opinion.

   1) You can wire an external trigger signal to an analog trigger input, on both boards.  If you configure your acquisition to be triggered on this external signal, they will start together.

   2) RTSI cable. It is an internal bus, that connects directly the 2 boards.  That is, from PCI board 1 to PCI board 2.  Then you can use RTSI signals to synchronize your acquisition.

   Of course, I supposed the 2 boards are on the same PC. Can you specify your meassurement system configuration?  Maybe, it can also help to know what's your measurement purpose.

   Hope it helps!!!! Let me know.... Have a nice day!


graziano

[lnc]

Thanks for your suggestion.  I have connected the two boards together using the RTSI cable. 

I have tried to set the source of the sampling clock to the first master device in DAQmxCfgSampClkTiming function call for the slave device.  However the outputs of the boards are not synchronized.  I'm not sure whether have I done it correctly.  Can anyone please advise?  Thank you. 

[devchander]

Hi

Plz attach the code you have developed so that we can suggest better

[Graziano]

Hi!
   Have you configured the RTSI cable in MAX?

   I'm no longer working with RTSI cables, so I can't check from here...... but I remember RTSI cable should be configured in MAX.  In MAX help, just search for RTSI.

   Hope it helps!

graziano

[Michael.Phillips]

Hello!

To configure a RTSI cable in MAX, right-click NI-DAQmx Devices and Select Create a new NI-DAQmx Device...RTSI cable.

You can use the DAQmxExportSignal function to export the sample clock and the start trigger to the other device through the RTSI cable.

Message Edited by Michael P on 02-17-2006 11:53 AM

[gcs]

In this situation, you don't need to use the DAQmxExportSignal function. If you specify a terminal on one device when configuring another device, and these devices are connected with a RTSI cable as specified in MAX, NI-DAQmx will automatically route the signal over the RTSI bus.

geoff

[Graziano]

Nice job, gcs!

[lnc]

Hello,

Thanks a lot for your help.  Managed to do the synchroniztion.  I added the RTSI cable in MAX and added in the codes:             

\\ Dev 1

DAQmxErrChk (DAQmxCreateTask("",&taskOut1));
DAQmxErrChk (DAQmxCreateAIVoltageChan(taskOut1,"Dev1\ai0" ,"",DAQmx_Val_Cfg_Default,minIn,maxIn,DAQmx_Val_Volts,NULL));

DAQmxErrChk (DAQmxCfgSampClkTiming(taskOut1,"",rateOut,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,bufferSize));

\\ Dev 2

DAQmxErrChk (DAQmxCreateTask("",&taskOut2));
DAQmxErrChk (DAQmxCreateAIVoltageChan(taskOut2,"Dev2\ai0","",DAQmx_Val_Cfg_Default,minIn,maxIn,DAQmx_Val_Volts,NULL));

\\ Change the source of the sample clock here

DAQmxErrChk (DAQmxCfgSampClkTiming(taskOut2,"\Dev1\ai\SampleClock",rateOut,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,bufferSize));

Thank you once again.