Create a waveform using PCI-6723 AO with various time intervals on trailing edge of sample clock of 200Hz and 0.1% duty cycle

[VJohnson]

I am using the PCI-6723 board and I am trying to attempt to produce a waveform pattern using the an analog output channel. The waveform consists of 5 different voltage levels. The main problem is that the first 4 voltage levels are expected to have time intervals of 926 microseconds and the time interval of the last voltage level is expected to be 1.296 milliseconds. Also, the waveform should be triggered on the trailing edge of a sample clock of 200Hz with a 0.1% Duty Cycle. Is this even possible? If so, any help would be greatly appreciated. Thanks in advance!

Here is what I currently have, but it does not accomplish my goal.

	int32	written;
	float64	data[5] = {-0.23, 0.38, 1.12, 1.78, 0.10};	//volts
	//long	time[5] = {  926,  926,  926,  926, 1296};	//microseconds

	// DAQmx Configure Clock
	DAQmxErrChk (DAQmxCreateTask("",&taskHandleFRQ));
	DAQmxErrChk (DAQmxCreateCOPulseChanFreq(taskHandleFRQ,"Dev3/ctr0","",DAQmx_Val_Hz,DAQmx_Val_Low,0,200,0.001));
	DAQmxErrChk (DAQmxCfgImplicitTiming(taskHandleFRQ,DAQmx_Val_ContSamps,1));

	// DAQmx Start Code
	DAQmxErrChk (DAQmxStartTask(taskHandleFRQ));

	// DAQmx Configure Code
	DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
	DAQmxErrChk (DAQmxCreateAOVoltageChan(taskHandle,"Dev3/ao0","",-10.0,10.0,DAQmx_Val_Volts,NULL));
	DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"/Dev3/Ctr0Out",1000.0,DAQmx_Val_Falling,DAQmx_Val_ContSamps,5));

	// DAQmx Write Code
	DAQmxErrChk (DAQmxWriteAnalogF64(taskHandle,5,0,10.0,DAQmx_Val_GroupByChannel,data,&written,NULL));

	// DAQmx Start Code
	DAQmxErrChk (DAQmxStartTask(taskHandle));

 

[VJohnson]

I have been working on some code all day to produce the waveform and associated clock and I believe that I am really close.

The code that I have shown here seems to trigger off the sample clock with a waveform around 1ms per step (the simple case).

However, when I try to bump up the sample rate to 800kHz and create my waveform from 4001 samples of data with the sample clock falling edge as the trigger (as seen in the commented code), the trigger no longer seems to be associated with the waveform.

Any ideas? I think I am almost there.

void CDevDlg::OnRdr1e1()
{
    float64    data[5] = {-0.23, 0.38, 1.12, 1.78, 0.10};    //volts
/*    float64        data[4001];
    float64        volt[5] = {-0.23, 0.38, 1.12, 1.78, 0.10};    //volts
    int x=0,d;

    for(int v=0; v<4; v++)
    {
        for(d=0; d<741; d++)
        {
            data[x++] = volt[v];
        }
    }
    for(d=0; d<1037; d++)
    {
        data[x++] = volt[4];
    }
*/
    // DAQmx Configure Clock
    DAQmxErrChk (DAQmxCreateTask("",&taskHandleFRQ));
    DAQmxErrChk (DAQmxCreateCOPulseChanFreq(taskHandleFRQ,"Dev3/ctr0","",DAQmx_Val_Hz,DAQmx_Val_Low,0,200,0.001));
    DAQmxErrChk (DAQmxCfgImplicitTiming(taskHandleFRQ,DAQmx_Val_ContSamps,5));
//    DAQmxErrChk (DAQmxCfgImplicitTiming(taskHandleFRQ,DAQmx_Val_ContSamps,800000));

    // DAQmx Start Code
    DAQmxErrChk (DAQmxStartTask(taskHandleFRQ));

    // DAQmx Configure Code
    DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
    DAQmxErrChk (DAQmxCreateAOVoltageChan(taskHandle,"Dev3/ao0","",-10.0,10.0,DAQmx_Val_Volts,NULL));
    DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",1000,DAQmx_Val_Rising,DAQmx_Val_ContSamps,5));
//    DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",800000,DAQmx_Val_Rising,DAQmx_Val_ContSamps,4001));
    DAQmxErrChk (DAQmxCfgDigEdgeStartTrig(taskHandle,"/Dev3/Ctr0Out",DAQmx_Val_Falling));

    // DAQmx Write Code
    DAQmxErrChk (DAQmxWriteAnalogF64(taskHandle,5,1,10.0,DAQmx_Val_GroupByChannel,data,NULL,NULL));
//    DAQmxErrChk (DAQmxWriteAnalogF64(taskHandle,4001,1,10.0,DAQmx_Val_GroupByChannel,data,NULL,NULL));
}

[VJohnson · Accepted solution]

Bingo. This code seems to be working much better. Seems like I needed to reduce my number of samples by 1 in order to fit the desired waveform within the sample clock's 5 millisecond period.

However, if anyone knows a better way of achieving these results, I am open for any ideas.

void CDevDlg::OnRdr1e1() 
{
	float64		data[4000];
	float64		volt[5] = {-0.23, 0.38, 1.12, 1.78, 0.10};	//volts
	int x=0,d;

	for(int v=0; v<4; v++)
	{
		for(d=0; d<741; d++)
		{
			data[x++] = volt[v];
		}
	}
	for(d=0; d<1036; d++)
	{
		data[x++] = volt[4];
	}

	// DAQmx Configure Clock
	DAQmxErrChk (DAQmxCreateTask("",&taskHandleFRQ));
	DAQmxErrChk (DAQmxCreateCOPulseChanFreq(taskHandleFRQ,"Dev3/ctr0","",DAQmx_Val_Hz,DAQmx_Val_Low,0,200,0.001));
	DAQmxErrChk (DAQmxCfgImplicitTiming(taskHandleFRQ,DAQmx_Val_ContSamps,800000));

	// DAQmx Start Code
	DAQmxErrChk (DAQmxStartTask(taskHandleFRQ));

	// DAQmx Configure Code
	DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
	DAQmxErrChk (DAQmxCreateAOVoltageChan(taskHandle,"Dev3/ao0","",-0.5,2.0,DAQmx_Val_Volts,NULL));
	DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",800000,DAQmx_Val_Rising,DAQmx_Val_ContSamps,4000));
	DAQmxErrChk (DAQmxCfgDigEdgeStartTrig(taskHandle,"/Dev3/Ctr0Out",DAQmx_Val_Falling));

	// DAQmx Write Code
	DAQmxErrChk (DAQmxWriteAnalogF64(taskHandle,4000,1,10.0,DAQmx_Val_GroupByChannel,data,NULL,NULL));
}

 

[marles]

Hello! I have a confusion regarding the following:

DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",800000,DAQmx_Val_Rising,DAQmx_Val_ContSamps,4000));
DAQmxErrChk (DAQmxCfgDigEdgeStartTrig(taskHandle,"/Dev3/Ctr0Out",DAQmx_Val_Falling));

Why did you specify DAQmx_Val_Rising on the first function call and DAQmx_Val_Falling on the second one? Wasn't it necessary to specify the same edge for the generating signal?