How to work around "invoke" error

Dear. All,

I have trouble occasionally failing to execute invoke commands.

I use the invoke command to retrieve measured waveform data from a digital oscilloscope, Tektronix DPO7254 for more than ten thousand times. But, I encountered with VISA communication error and the execution of the m-script file was stopped. It seems this error happens only once over thousands of executions. It is very helpful if someone explains how to workaround VISA error and retry invoke commands by using mscript.

My program include scripts as follows,

deviceObj = icdevice('DPO7254.mdd', interfaceObj);
set(interfaceObj, 'OutputBufferSize', 2*DSO_DATA_SIZE+10000);
connect(deviceObj);
groupObj = get(deviceObj, 'Waveform');
set(deviceObj.Waveform(1), 'Precision', 'int16');
[CH1,T_measure] = invoke(groupObj, 'readwaveform', 'channel1',true);
[CH2,T_measure] = invoke(groupObj, 'readwaveform', 'channel2',true);
[CH3,T_measure] = invoke(groupObj, 'readwaveform', 'channel3',true);
[CH4,T_measure] = invoke(groupObj, 'readwaveform', 'channel4',true);

Best Regards

W. I.

Answer 1

[Amith]

Hi Ima,

To handle VISA errors and retry invoke commands in MATLAB, you can use a combination of error handling and retry logic. Here’s a basic example of how you might structure your script to achieve this:

1. Define your device and connection settings:

deviceObj = icdevice('DPO7254.mdd', interfaceObj);
set(interfaceObj, 'OutputBufferSize', 2*DSO_DATA_SIZE + 10000);
connect(deviceObj);
groupObj = get(deviceObj, 'Waveform');
set(deviceObj.Waveform(1), 'Precision', 'int16');

2. You can Implement error handling and retry logic similar to the below logic:

maxRetries = 3; % Maximum number of retries
retryCount = 0;
success = false;

while ~success && retryCount < maxRetries
    try
        [CH1, T_measure] = invoke(groupObj, 'readwaveform', 'channel1', true);
        [CH2, T_measure] = invoke(groupObj, 'readwaveform', 'channel2', true);
        [CH3, T_measure] = invoke(groupObj, 'readwaveform', 'channel3', true);
        [CH4, T_measure] = invoke(groupObj, 'readwaveform', 'channel4', true);
        success = true; % If no error, set success to true
    catch ME
        retryCount = retryCount + 1;
        fprintf('Error occurred: %s\n', ME.message);
        fprintf('Retrying %d/%d...\n', retryCount, maxRetries);
        pause(1); % Pause before retrying
    end
end

if ~success
    error('Failed to read waveform after %d attempts.', maxRetries);
end

The above code attempts to read waveforms from the oscilloscope up to three times if an error occurs. If the command fails after the maximum number of retries, it throws an error.

To resolve VISA issues you can refer to these documentation provided by MathWorks:

• https://www.mathworks.com/help/instrument/resolve-visa-connection-errors.html
• https://www.mathworks.com/help/instrument/troubleshooting-visa-interface.html

Hope this helps!