sometimes the function triggers when i trigger the sensor, sometimes it triggers without me triggering it, sometimes it won't trigger even through multiple attempts.

hi, I am new to this and I have problem with my function. For some reason the software can't sense when I trigger the sensor or it triggers without me triggering the sensor. The result was so random and I couldn't find the problem. Thank you for reading this.

function [accelDataArray, accelDataArray2] = collectSamples(serialObject1, sampleNum, serialObject2, sampleNum2)
sampleCounter1 = 1;
accelDataArray = zeros(sampleNum, 1);
sampleCounter2 = 1;
accelDataArray2 = zeros(sampleNum2, 1);
triggered = false;  % Initialize the trigger condition
% Wait for the trigger condition (preliminary loop)
disp('Waiting for trigger...');
%%fix 282 to 312
while ~triggered
    if serialObject1.BytesAvailable < 20 || serialObject2.BytesAvailable < 20
        continue;
    end
    header1 = fread(serialObject1, 1);
    header2 = fread(serialObject2, 1);
    if header1 ~= 85 || header2 ~= 85
        fread(serialObject1, 1);
        fread(serialObject2, 1);
        continue;
    end
    dataBytes1 = fread(serialObject1, 19);
    dataBytes2 = fread(serialObject2, 19);
    if dataBytes1(1) ~= 97 || dataBytes2(1) ~= 97
        continue;
    end
    azL = dataBytes1(6);
    azH = dataBytes1(7);
    az = double(typecast(uint8([azL azH]), 'int16')) / 32768 * 16;
    azL2 = dataBytes2(6);
    azH2 = dataBytes2(7);
    az2 = double(typecast(uint8([azL2 azH2]), 'int16')) / 32768 * 16;
    if az > .1 || az2 > .1  % Trigger condition, adjust the threshold as needed
        triggered = true;
        disp('Triggered, now collecting samples...');
    end
end
% Data collection loop
while sampleCounter1 <= sampleNum || sampleCounter2 <= sampleNum2
    % Read data from sensor 1
    if serialObject1.BytesAvailable >= 20
        header1 = fread(serialObject1, 1);
        if header1 == 85
            dataBytes1 = fread(serialObject1, 19);
            if dataBytes1(1) == 97
                azL = dataBytes1(6);
                azH = dataBytes1(7);
                az = double(typecast(uint8([azL azH]), 'int16')) / 32768 * 16;
                accelDataArray(sampleCounter1) = az;
                sampleCounter1 = sampleCounter1 + 1;
            end
        end
    end
    % Read data from sensor 2
    if serialObject2.BytesAvailable >= 20
        header2 = fread(serialObject2, 1);
        if header2 == 85
            dataBytes2 = fread(serialObject2, 19);
            if dataBytes2(1) == 97
                azL2 = dataBytes2(6);
                azH2 = dataBytes2(7);
                az2 = double(typecast(uint8([azL2 azH2]), 'int16')) / 32768 * 16;
                accelDataArray2(sampleCounter2) = az2;
                sampleCounter2 = sampleCounter2 + 1;
            end
        end
    end
end
end

Answer 1

[Kautuk Raj]

I can observe that you are experiencing inconsistent behaviour with your function, where it sometimes triggers the sensor correctly, sometimes triggers without any input, and sometimes fails to trigger despite multiple attempts.

This inconsistency could stem from several issues:

1. Check Serial Data Availability: Ensure that enough data is available before attempting to read.
2. Validate Headers and Data: Add more checks to validate the headers and data bytes.
3. Adjust Trigger Threshold: Make the trigger threshold configurable.
4. Add Timeout: Add a timeout (using the 'pause' function) to avoid infinite loops in case the trigger condition is never met.

You can refer to the following resources from the MATLAB documentation:

Serial communication and availability: https://www.mathworks.com/help/matlab/serial-port-devices.html

Datatype validation and conversion: https://www.mathworks.com/help/matlab/ref/typecast.html

Timing: https://www.mathworks.com/help/matlab/ref/pause.html

I hope this helps with your query.