How to Output Scans to DAQ but Ignore Digital Outputs

Hello All,

I have a DAQ USB-6003 interfacing with Matlab. I currently have 1 analog input, 1 digital output, and 1 analog output. I understand that I can use 'write' command to output to the DAQ. However, because I have a digital output with no clock, it tells me that "on-demand" operations only are available for that channel.

Therefore, if I try to use an MxN scan matrix to send using the 'write' command, it throws an error (see image). I am wondering if there is a way to only output to the analog channel(s) and ignore the digital channel.

Thanks

Answer 1

[Umar]

Hi Holden,

After reviewing your comments, please ensure that your scan matrix is correctly configured. Make sure that only the analog channels you want to write to are included in the scan matrix. Let me provide example of how you can create a scan matrix in Matlab for analog output:

% Define your analog output channels
analogChannels = [0 1]; % Specify the analog channels you want to use
% Create a scan matrix with values for analog output
scanMatrix = [0.5 1; 0.3 0.7]; % Example values for analog output
% Write the scan matrix to the analog output channels
outputData = scanMatrix';
writeData = [analogChannels; outputData];
write(s, writeData); % Assuming 's' is your analog output session

Please ensure that the analogChannels array contains the indices of the analog channels you want to use, and the scanMatrix contains the values you want to output to those channels.

Hope this will help resolve your problem.

[Holden]

Thanks for the info. I will give this a try.

I have one more pressing issue. I want to do some continuous sampling using "start" function of my analog channels, but because I have some digital ports, it also gives me the error of "on demand" operations only. Is there a similar fix to start reading data from just the analog ports so that it can be continuous?

Thanks for the help

[Holden]

I think I figured it out, I can create separate DAQ sessions and add the digital ports to one, and the analog to the other, and then I am able to do continuous scanning with the second analog session so it is working now!

[Umar]

Hi Holden,

Glad to hear your problem is resolved. Let me know if you need further assistance.

[Umar]

To provide suggestions towards your earlier comment about I want to do some continuous sampling using "start" function of my analog channels, but because I have some digital ports, it also gives me the error of "on demand" operations only. Is there a similar fix to start reading data from just the analog ports so that it can be continuous? Yes, you can specify the channels explicitly for analog input. By creating an analog input object and specifying only the analog channels, you can avoid the "on demand" operations error caused by digital ports. Here's a simple example to demonstrate this:

% Create an analog input object
ai = analoginput('winsound');
addchannel(ai, 0:1); % Add only the analog channels you want to sample
% Configure the acquisition parameters
ai.SampleRate = 1000; % Set the sampling rate
ai.SamplesPerTrigger = Inf; % Continuous sampling
% Start the acquisition
start(ai);
% Retrieve and plot the data
data = getdata(ai);
plot(data);

So, explicitly adding only the analog channels you wish to sample, you can ensure continuous data acquisition without being affected by digital port.

[Holden]

Good to know, looks like both ways work, Thanks!

[Umar]

No problem Holden, we are glad that your problems are resolved. Happy 4th of July.