write cannot be porformed because number of channels in the data does not match number of channels in the task

[idanbis]

hello,

i'm trying to write analogs from buffer to several channels using NI-6723.

For some reason, everytime I pass to function double buffer (1D) that holds buffers for all channels,

i always end up with excpetion saying the numbers of channels in the data is "1".

i'm using c#:

Task m_TaskHandle = new Task();

string sChannelsList = "Dev2/ao21:23";



m_TaskHandle.AOChannels.CreateVoltageChannel(

sChannelsList,

"", 0, 5, AOVoltageUnits.Volts );





int iNumberOfSamples = 4;

double dSamplingFrequency = 1000;

m_TaskHandle.Timing.ConfigureSampleClock("",

dSamplingFrequency,

SampleClockActiveEdge.Rising,

SampleQuantityMode.ContinuousSamples,

iNumberOfSamples /* Only relevant if mode is FiniteSamples */);


// Data code is here
double[] adSampleBuffer;
// array values removed from this code snippet (here i have function that generates data)
// array size is: num_of_samples * total_channels (in this case 4 * 3)


AnalogSingleChannelWriter ChanWriter = new AnalogSingleChannelWriter(m_TaskHandle.Stream);



ChanWriter.WriteMultiSample(false, adSampleBuffer);

m_TaskHandle.Start();

 

Not sure what am i missing, how does the MSTDIO determine the "number of channels in data", as i keep getting in exception it's always equals to 1.

would appricate any help.

thanks.

[Anzurio · Accepted solution]

Hi idanbis,

As for the code snippet you posted, you are creating more than one channel by using the range ao21:23. Given this, you should be using AnalogMultiChannelWriter to setup your writing operation instead of AnalogSingleChannelWriter.

In order to write using AnalogMultiChannelWriter::WriteMultiSample(boolean, double[,]), you should know that the data you want to write should be stored in a 2D array. Each element in the first dimension of this array corresponds to a channel in the task, while each element in the second dimension, corresponds to a sample to write to its corresponding channel. For instance, let:

double  [,]  data = new double[numChannels, numSamplesPerChannel];

Then:

data[0,0...numSamplesPerChannel]; // This is the set of all the samples in the first channel (ao21 in your code).

I hope this was helpful. Let me know if I left doubts remaining.

Best regards,

Anzurio

[idanbis]

That solved it.

Thank you for the fast reply.