I see that you are performing a background sampling of a DAQ USB6003 in MATLAB and you need to periodically pull the latest data point from the background sampling.
The error you are encountering, "NI Error -50103", indicates that the resource is reserved, meaning that the DAQ device is already in use by another task. This is a common issue when attempting to access the same DAQ device from multiple tasks simultaneously.
Here are a few strategies you can try to resolve this issue and periodically access the latest data points:
Use a Listener to Access Data - MATLAB allows you to set up a listener that can be triggered whenever new data is available. This approach avoids directly accessing the DAQ device while it is in use.
s = daq.createSession('ni'); % Create a DAQ session
addAnalogInputChannel(s, 'Dev1', 'ai0', 'Voltage');
s.Rate = 1000; % 1000 Hz
s.DurationInSeconds = 10;
% Add a listener for DataAvailable event
lh = addlistener(s, 'DataAvailable', @(src, event) processData(event));
function processData(event)
latestData = event.Data(end, :); % Get the latest data point
disp(latestData);
end
s.startBackground();
Use a Circular Buffer - Implement a circular buffer to store the latest data points and access them as needed. This approach can be combined with the listener method.
bufferSize = 1000;
circularBuffer = zeros(bufferSize, 1);
bufferIndex = 1;
function processData(event)
global circularBuffer bufferIndex bufferSize;
data = event.Data;
numDataPoints = size(data, 1);
for i = 1:numDataPoints
circularBuffer(bufferIndex) = data(i);
bufferIndex = mod(bufferIndex, bufferSize) + 1;
end
% Access the latest data point
latestData = circularBuffer(mod(bufferIndex - 2, bufferSize) + 1);
disp(latestData);
end
Please refer to the following MATLAB Answer for better understanding
I hope this helps.
