get continuous data in while loop through serial

Question

Sharah 2019-1-18

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https://ww2.mathworks.cn/matlabcentral/answers/440370-get-continuous-data-in-while-loop-through-serial

编辑： Sharah 2019-1-18

Hello,

I need help with reading data from serial. Basically I have arduino that sends data "0" or "1" randomly every 2-4 seconds. When I save this data i will get 0 or 1. However, what I want is a continuous data, i.e. even when the true or false does not change, i still can record that. in this case have an array of 0 or 1 instead of 01010101. how can i do this? my code:

s = serial('COM13', 'BaudRate', 115200);
fopen(s);
y=[];
t1 = tic;
while (t<10)
    x = fscanf(s)
    t = toc(t1);
    y = [y; t, x] % right now it's only 010101, but i want eg 00000011111111111110001111...
    %with time stamp
end

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Answer 1

Walter Roberson 2019-1-18

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https://ww2.mathworks.cn/matlabcentral/answers/440370-get-continuous-data-in-while-loop-through-serial#answer_356958

You can test the BytesAvailable property of the port. If it is 0 then repeat your most recent reading . You might want to configure a timer object to sample at appropriate frequency .

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Walter Roberson 2019-1-18

It would be 0 except when data has been received but not processed . Your current fgets is blocking waiting for a complete line so you would need to be using a timer to detect the situation as timers should be able to interrupt the wait.

You should reorganize . Don't use while . Use BytesAvailableFcn to trigger the fgets and store the result in a known place . use aa timer object set to repeat at your desired sampling frequency . The timer should retrieve the current value from the known location and leave the value there . If the timer fires again before the BytesAvailable callback has read in the next value then the same value as before will be read.

Sharah 2019-1-18

编辑：Sharah 2019-1-18

Actaully I made a mistake before and using the BytesAvailable works now. Many thanks for the suggested answer. DO you know any sample code that shows BytesAvailableFcn? I have never used it before. I need to read and store the data at 100Hz.

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