Warning in reading data from serial port.

Question

Sabarinathan Vadivelu 2013-8-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/84966-warning-in-reading-data-from-serial-port

I'm trying to read a single character 'A' from serial port, But it is issuing a warning always.

CharVar = fscanf(SerialObj,'%c',1);
Warning: Unsuccessful read: A timeout occurred before the Terminator was reached or SIZE values were available.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2013-8-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/84966-warning-in-reading-data-from-serial-port#answer_94495

The message seems to tell you, that Matlab did not receive a character and/or the corresponding terminator before the timeout occurred. So it might be useful to show us the command used for opening the port (especially the timeout value) and explain, if you are sure, that the character has been sent in the required period of time.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Sabarinathan Vadivelu 2013-8-19

在 MATLAB Online 中打开

SerialObj = serial('COM1');
set(SerialObj,'BaudRate',9600)
vid = videoinput('winvideo', 1, 'YUY2_640x480');
src = getselectedsource(vid);
vid.FramesPerTrigger = 1;
vidRes = get(vid, 'VideoResolution');
nBands = get(vid, 'NumberOfBands');
hImage = image(zeros(vidRes(2),vidRes(1),nBands));
preview(vid,hImage);
vid.ReturnedColorspace = 'rgb';
axes(handles.axes1);
fopen(SerialObj);
try
    while(1)
        % preview(vid,hImage);
        % drawnow;
        CharVar = fscanf(SerialObj,'%c',1);
        if ~isempty(CharVar)
            if strcmp(CharVar(1),'A')
                while(1)
                    capturedImage = getsnapshot(vid);
                    faceDetector = vision.CascadeObjectDetector();
                    bboxes = step(faceDetector, capturedImage);
                    faceRegion = imcrop(capturedImage,bboxes);
                    faceRegion = rgb2gray(faceRegion);
                    obj = fspecial('unsharp');
                    faceRegion = imfilter(faceRegion,obj);
                    faceRegion = imresize(faceRegion,[400 400]);
                    imshow(faceRegion)
                    % fclose(SerialObj);
                      facePoints = detectSURFFeatures(faceRegion,'MetricThreshold',10);
                      [faceFeatures, facePoints] = extractFeatures(faceRegion, facePoints);
                      load FaceDatabase.mat
                      for i = 1 : count
                          boxPairs = matchFeatures(faceFeatures, SurfFeatures(i).features);
                          dataPoints = facePoints(boxPairs(:, 1), :);
                          queryPoints = SurfFeatures(i).points(boxPairs(:, 2), :);
                          PointsArray(i).data = dataPoints;
                          PointsArray(i).query = queryPoints;
                          countArray(i) = queryPoints.Count;
                      end
                      [maxValue,maxIdx] = max(countArray);
                      if maxValue > 30
                          % figure;
                          % showMatchedFeatures(SurfFeatures(maxIdx).face, faceRegion, PointsArray(maxIdx).data, ...
                          %     PointsArray(maxIdx).query, 'montage');
                          % title('Putatively Matched Points');
                          helpdlg(['Authorized, Face ID : ' num2str(maxIdx)],'Welcome');
                          fwrite(SerialObj,'A');
                          pause(10);
                          % [CharVar,CountVar,msg] = fscanf(SerialObj,'%c');
                          % if strcmp('S',CharVar(1))
                          %     fwrite(SerialObj,'B');
                          %     break;
                          % end
                      else
                          errordlg('Un-Authorized','Sorry');
                          fwrite(SerialObj,'B');
                          break;
                      end
                  end
                  continue;
              end
          else
              preview(vid,hImage);
              drawnow;
          end
      end
      fclose(SerialObj);
  catch
      fclose(SerialObj);
  end

Sabarinathan Vadivelu 2013-8-19

编辑：Sabarinathan Vadivelu 2013-8-19

在 MATLAB Online 中打开

This is my code. In this part,

CharVar = fscanf(SerialObj,'%c',1);

The warning was issued. But I receive the character in MATLAB. The main Problem is the delay.

Jan 2013-8-25

What about increasing the value of the TimeOut?

请先登录，再进行评论。

Warning in reading data from serial port.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

回答（1 个）

3 个评论
显示 1更早的评论隐藏 1更早的评论

另请参阅

类别

标签

Community Treasure Hunt

Warning in reading data from serial port.

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

回答（1 个）

3 个评论 显示 1更早的评论隐藏 1更早的评论

另请参阅

类别

标签

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

3 个评论
显示 1更早的评论隐藏 1更早的评论