First fscanf(s) returns an empty array.

Question

Reuben 2013-10-22

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/91023-first-fscanf-s-returns-an-empty-array

回答： David Sanchez 2013-10-22

Almost every first read of fscanf() returns a empty array. Am I not setting up fopen correctly? Other than the first read, everything works fine. (The empty array causes problems when trying to save the value. My intention is to make this as simple as possible because the code is for first year programming students) Thank you.

clc
delete(instrfindall)
socket = serial('COM12','BAUD',57600);
fopen(socket);
pause(3);
for i = 1:30  
      data = str2num(fscanf(socket,'%s'));         
      disp ([data, length(data),isempty(data)])    
      raw_data(i) = data;
end

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Answer 1

David Sanchez 2013-10-22

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https://ww2.mathworks.cn/matlabcentral/answers/91023-first-fscanf-s-returns-an-empty-array#answer_100463

You say "almost" every first reading of the serial port returns an empty array. That could mean that there's nothing in the buffer "almost" every first reading and your code is fine. Make sure the devices are properly synchronized and something was sent beforehand when you try to read.

Use isempty to avoid saving the empty string.