How to read mutiple channels simultaneously in vc++

[EdwardNewGaite]

Previously, I create a task to read 6 channels in vc++. The method I use is reading eatch channel separately. Here, problem rising! One channel take one second, and six is six seconds. It's too long to my control system. So I want to read them simultaneously. One sulotion I know is using multithreading, but I dont think it is the best. I believe there are other sulotions in DAQmx.

Here is the main code i use now:

DAQmxCreateTask("",&DAQtask);
DAQmxCreateAIVoltageChan(DAQtask,"Dev1/ai0:5","",DAQmx_Val_Cfg_Default,-5.0,5.0,DAQmx_Val_Volts,NULL);

DAQmxCfgSampClkTiming(DAQtask,"",1000.0,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,N);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai0");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData1,N,&read1,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai1");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData2,N,&read2,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai2");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData3,N,&read3,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai3");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData4,N,&read4,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai4");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData5,N,&read5,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai5");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData6,N,&read6,NULL);
DAQmxStopTask(DAQtask);

DAQmxClearTask(DAQtask);

Thank you for your reply!

[EdwardNewGaite]

The board I use is PCI 6221. I'm afread the multithread cannot work...

[altenbach]

Since you posted in the LabVIEW forum, please explain how the question is related to LabVIEW. I don't quite see it.

[Bob_Schor]

This is almost trivial to do in LabVIEW using DAQmx.  Depending on what you want to do with the data from the six (simultaneously-acquired) Analog channels, you could probably use 3 or 4 DAQmx functions, a While loop, a Stop Control, and maybe a Chart.

Bob Schor

[santo_13]

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@EdwardNewGaite wrote:

Previously, I create a task to read 6 channels in vc++. The method I use is reading eatch channel separately. Here, problem rising! One channel take one second, and six is six seconds. It's too long to my control system. So I want to read them simultaneously. One sulotion I know is using multithreading, but I dont think it is the best. I believe there are other sulotions in DAQmx.

Here is the main code i use now:

DAQmxCreateTask("",&DAQtask);
DAQmxCreateAIVoltageChan(DAQtask,"Dev1/ai0:5","",DAQmx_Val_Cfg_Default,-5.0,5.0,DAQmx_Val_Volts,NULL);

DAQmxCfgSampClkTiming(DAQtask,"",1000.0,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,N);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai0");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData1,N,&read1,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai1");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData2,N,&read2,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai2");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData3,N,&read3,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai3");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData4,N,&read4,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai4");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData5,N,&read5,NULL);
DAQmxStopTask(DAQtask);

DAQmxStartTask(DAQtask);
DAQmxSetReadChannelsToRead(DAQtask, "Dev1/ai5");
DAQmxReadAnalogF64(DAQtask,-1,10.0,DAQmx_Val_GroupByChannel,OriginData6,N,&read6,NULL);
DAQmxStopTask(DAQtask);

DAQmxClearTask(DAQtask);

Thank you for your reply!

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The technique is to put all 6 channels in the same task, and use read/write N channels function with that multi-channel task.

[GerdW]

Hi,

you all answered a 9 year old thread… 😄

(I guess this was triggered by a SPAM message, which is already removed by now.)

[altenbach]

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@GerdW wrote:

Hi,

you all answered a 9 year old thread… 😄

(I guess this was triggered by a SPAM message, which is already removed by now.)

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Actually, they just posted in the version conversion forum, after which I looked at the profile and saw some unread messages, then assumed they were new too. I should have looked more closely.... 😉

[santo_13]

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@GerdW wrote:

Hi,

you all answered a 9 year old thread… 😄

(I guess this was triggered by a SPAM message, which is already removed by now.)

---

Facepalm moment!

[rolfk]

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@GerdW wrote:

Hi,

you all answered a 9 year old thread… 😄

(I guess this was triggered by a SPAM message, which is already removed by now.)

---

It's still in the wrong forum though! 😀