Analog Output Multiple Channel Write Configuration

[lei-maru]

Hi,

I'd like to write into multiple channels Analog Outputs and my doubts are around  the configuration of the timing and buffer.

Let's put an example:

double SamplesPerChannel = 1000.0;

double ao1_freq = 100;

double a01_amp = 2.0;

double ao2_freq = 20;

double a02_amp = 1.0;

double dataToWrite[2000]; // buffer os size =numChannels *SamplesPerChannel

int        numChannels = 2;

int        i=0;

double sampleClockRate = a01_freq*SamplesPerChannel ; //I've used the maximum frequency

for (i=0; i<SamplesPerChannel ;i++)

{

    data[i] = amplitude*sin((double)i*2.0*PI/SamplesPerChannel );

}

for (i=SamplesPerChannel ; i<SamplesPerChannel *numChannels ;i++)

{

    data[i] = amplitude*sin((double)i*2.0*PI/SamplesPerChannel );

}

 DAQmxCreateTask("",&taskHandle);
 DAQmxCreateAOVoltageChan(taskHandle,"cDAQ1Mod4/ao0","",-10.0,10.0,DAQmx_Val_Volts,NULL);
 DAQmxCreateAOVoltageChan(taskHandle,"cDAQ1Mod4/ao1","",-10.0,10.0,DAQmx_Val_Volts,NULL);
 DAQmxCfgSampClkTiming(taskHandle,"",sampleClockRate ,DAQmx_Val_Rising,DAQmx_Val_ContSamps,XXX);

 DAQmxRegisterDoneEvent(taskHandle,0,DoneCallback,NULL);

 DAQmxWriteAnalogF64(taskHandle,SamplesPerChannel ,0,10.0,DAQmx_Val_GroupByChannel,dataToWrite,NULL,NULL);

 DAQmxStartTask(taskHandle);

..............

1.- ¿Is correct the way I've calculated the sampleClockRate ? ¿ Or should it be: sampleClockRate=a01_freq*SamplesPerChannel *numChannels?

2.- XXX is the buffer size, but again I'm not sure if it should be 2000(numChannels *SamplesPerChannel ) or 1000 (SamplesPerChannel ).

As you can see my problem is to understand how affects having more than one channel in the timing configuration.

Thanks in advance

[JaimeC]

Hi,

The sample clock rate specified is for ALL the channels that means, if you put a clock rate of 20.000 and u have 5 channels, all channels will be scanned at 20.000 samples per second (20.000 samples/s at channel .0, 20.000 samples / s at channel 1, etc...)

The same is for the buffer size the buffer size specified is per channel. So a 5000 for example would mean 5000 samples buffer for each channel (5000 for channel 0, 5000 for channel 1, etc...)

Hope that helps,