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Line Scan Camera

Read the data from a line scan camera

Add-On Required: This feature requires the Simulink Coder Support Package for NXP FRDM-KL25Z Board add-on.

Library

Simulink Coder Support Package for NXP FRDM-KL25Z Board/ FRDM-TFC Shield

  • Line Scan Camera block

Description

Read the data from the selected line scan camera. The block input specifies the exposure time of the camera in milliseconds. The block input accepts values between 0–150 ms. The block output emits a [1x128] array of uint16 values. Setting an exposure time greater than the sample time of this block can cause nondeterministic behavior.

During simulations, this block output emits emulated camera data in the form of an array of [1x128] uint16 values. The data emulated is similar to what the camera produces, when a dark line moves from left to right on a white background in the form of a sine wave.

You can change the simulation behavior by opening the block code and by modifying it in the stepImpl function.

To modify the block code, perform the following steps:

  1. Go to the MATLAB® prompt and enter the following command.

    edit freedomboard.LinescanCamera

  2. Modify the following code in the stepImpl function.

      elseif ( coder.target('Sfun') )
         cameraData = uint16(zeros(1,128));
				% example Simulation code
          % background light intensity
          bkgIntensity  = 18000;
          % intensity of the line to follow
          lineIntinsity =  3500;
            
          ambientOffset = (bkgIntensity - lineIntinsity)*0.75;
                
         	% specify how many pixels wide the line should be
         lineWidth = 46;
         create a curve to simulate the ambient light reflecting off of 
         the track baseBluntness = 1.25;
         baseLine = int16( (sqrt((1+baseBluntness^2)./...
         (1+baseBluntness^2*sin((0:pi/127:pi)).^2))...
          .*sin(0:pi/127:pi))...
           * (bkgIntensity-ambientOffset)) + ambientOffset;
                
          % calculate the position of the start of the dip created by
          % the dark line on the track.  This is how we control the position 
          of the line at each simulated sample
            startIdx = uint8(sin((pi/200)*obj.simSampleNum)*63+64);
          % calculate the end index of the darkDip, but make sure it
          % does not exceed the length of the array (128)
          if((startIdx + uint8(lineWidth-1)) > uint8(128))
           endIdx = uint8(128);
           else
            endIdx = startIdx + uint8(lineWidth-1);
          end
                
          % create a curve which emulates the dark line's affect on the camera
          baseHeight = double(baseLine(startIdx:endIdx));
          baseHeight = [baseHeight, repmat(bkgIntensity, 1, 
           lineWidth - length(baseHeight))];
          bluntness = 1.75;
          darkDip  = uint16( (sqrt((1+bluntness^2)./...
          (1+bluntness^2*sin((0:pi/(lineWidth-1):pi)).^2))...
          .*sin(0:pi/(lineWidth-1):pi))...
          .* (baseHeight - lineIntinsity*0.75));
               
          % combine the darkDip and the baseLine at the calculated location
 cameraData(:) = baseLine;
 cameraData(startIdx:endIdx) = cameraData(startIdx:endIdx) - 
 darkDip(1:endIdx-startIdx+1);
          % threshhold the dip so that we have a flat section at the line
          cameraData(cameraData < lineIntinsity) = lineIntinsity;
                
           % add noise to the data
           noise = randi(lineIntinsity*0.05, size(cameraData), 'uint16');
cameraData(mod(1:length(cameraData), 2) == 0) = 
cameraData(mod(1:length(cameraData), 2) == 0) 
- noise(mod(1:length(cameraData), 2) == 0);
cameraData(mod(1:length(cameraData), 2) ~= 0) = 
cameraData(mod(1:length(cameraData), 2) ~= 0) 
+ noise(mod(1:length(cameraData), 2) == 0);

          % iterate the simulation Sample Number
          obj.simSampleNum = obj.simSampleNum + 1;
	  end

  3. Save the MATLAB file.

  4. Change the MATLAB current directory to the folder that contains LinescanCamera.m file.

  5. Create a protected function file for the MATLAB file using the following command in the MATLAB prompt.

    pcode freedomboard.LinescanCamera

  6. Run the following commands in the MATLAB prompt

    clear pcode

    clear classes

    rehash toolboxcache.

The block is updated with your new simulation behavior.

Parameters

Camera

Select Camera 0 or Camera 1.

Sample time

Specify how often this block reads the line scan camera data.