Specify the Initialization, Output, and Termination

Step 4 of 6 in Create a Digital Read Block

The setupImpl and stepImpl methods hook the C functions to the System object™. The initialization of a digital pin as output needs to be done only once at model initialization. Hence, the digitalIOSetup function is called in setupImpl. To update the logic state of the digital output pin, a call to readDigitalPin is made from the stepImpl method. Nothing needs to be done at termination. Follow these steps to update the initialization, output, and termination code sections of the DigitalRead System object you created in Select System Object Template.

1. In the MATLAB^® Editor, open DigitalRead.m.

2. Update the setupImpl method using the following code.

   methods (Access=protected)
       function setupImpl(obj) %#ok<MANU>
           if isempty(coder.target)
               % Place simulation setup code here
           else
               % Call C-function implementing device initialization
               coder.cinclude('digitalio_arduino.h');
               coder.ceval('digitalIOSetup', 9, 0);
           end
       end
       ...
   end

   The coder.ceval function executes calls to the C wrapper functions in digitalio_arduino.h. The second and third arguments of coder.ceval are the Arduino^® hardware pin number and value, respectively.

3. Update the BuildInfo method using the following code.

   methods (Static)
       ...
       function updateBuildInfo(buildInfo, context)
           if context.isCodeGenTarget('rtw')
               % Update buildInfo
               srcDir = fullfile(fileparts(mfilename('fullpath')),'src'); %#ok     
               includeDir = fullfile(fileparts(mfilename('fullpath')),'include');                 
               addIncludePaths(buildInfo,includeDir);
               % Use the following API's to add include files, sources and linker flags
               addSourceFiles(buildInfo,'digitalio_arduino.cpp', srcDir);
           end
       end
       ...
   end

4. Update the stepImpl method with the following code.

   methods(Access=protected)
       ...
       function y = stepImpl(obj) %#ok<MANU>
           y = double(0);
           if isempty(coder.target)
               % Place simulation output code here
           else
               % Call C-function implementing device output
               y = coder.ceval('readDigitalPin', 9);
           end
       end
       ...
   end

   Unlike the DigitalWrite System object, the stepImpl method for the DigitalRead System object defines an output, y, which is the logical value of the chosen pin.

5. Update the releaseImpl method with the following code.

   methods(Access=protected)
       ...
       function releaseImpl(obj) %#ok<MANU>
           if isempty(coder.target)
               % Place simulation termination code here
           else
               % Call C-function implementing device termination
               % No termination code for Arduino
           end
       end
       ...
   end

In the next section, you will Set Output Port Properties of your system object.