MATLAB: How to edit the generated code to save output to TXT file

codecodegencustomEmbedded Coderfilematoutputsavetext;timetxtvalues

I have modified the Configuration Parameters -> Custom Code to save the outputs to a text file like this:

#include <stdio.h>
FILE * pFile;
pFile = fopen ("myfile.txt","w");
fprintf(pFile,"%f \n", myModel_Y.Out1 );
fclose (pFile);

This just gives me the last value of the Simulation. Is there a simple way to save all values (including the time values)?

Best Answer

Implementing the above code by adding it to Configuration Parameters, you will only see the last output. This is the expected behavior as the model executes in real time; therefore, when the model terminates, it actually has only the last data to throw out to the TXT file. There are many ways to achieve this, and one possible (and simplest) way is to modify the generated code instead of having it included in the Custom Code section.

An example model is attached and below is a procedure to achieve this workflow. You will have to generate the code yourself because it is compiler dependent. However, I am also attaching a .C file that was generated by Simulink Coder to which I made the changes in order to save the time and output values to a TXT File.

Here are the steps you need to follow:

1. Open the model custom_code_example.slx. It's a simple model that adds a noise to a sine wave. Run the model and see the output on scope. Do not make any changes to Configuration Parameters, but notice that the Custom Code section is empty.

                            <Output of the Scope>

2. Go ahead and build the Model to generate code. This will create a new folder "code_gen_example_grt_rtw". Go into this folder and notice 3 files that we would be using:

code_gen_example.c - We will modify this file
code_gen_example.bat - We will execute this batch file to update our modified C file above.
code_gen_example.exe - This will be created by the BAT file above.

I have attached the modified code_gen_example.c file with the changes made that I will describe in the next step. This file is for your reference only. You would need to make similar changes to the C file generated by your compiler.

3. Open the code_gen_example.c file and notice that I have added the #include "stdio.h" at Line 19 and a global file pointer File *pFile the top of the C file.

4. Now notice line 158 - 160 in attached C file. Here I have added the following code:

// Open a Text file for writing
printf("\n\nOpening Text File\n\n");
pFile = fopen ("myfile.txt","w");

Notice that this is in the code_gen_example_initialize function. The <model_name>_initialize function is called once when the model is loaded into memory. Here we are just opening the text file.

5. Similarly, when the model terminates or finishes executing, we need to close the TXT File. For this, I have added the following code in line 358-359 of code_gen_example_terminate function.

printf("\n\nClosing Text File\n\n");
fclose(pFile);

6. Next, we need to save the time and output values every time step the model executes. The C-function that is called to calculate the outputs is code_gen_example_step. In this function, notice that I added the following code at line 97 to save the time and output values to the TXT file:

fprintf(pFile,"%f, %f\n",code_gen_example_M->Timing.t[0],code_gen_example_Y.Out1 );

7. Now since the C-code is modified, we need to build the model EXE again to reflect these changes. To do so, we will execute the BAT file in the shell. Execute the following command in MATLAB Command Window to remake all the files

>> !code_gen_example.bat

This will build the new code_gen_example.exe file in the current folder. The following would be displayed on Command Window:

### Creating standalone executable "..\code_gen_example.exe" ... 
    link /RELEASE  /INCREMENTAL:NO /NOLOGO -subsystem:console,5.02 kernel32.lib  ws2_32.lib mswsock.lib advapi32.lib -out:..\code_gen_example.exe @code_gen_example.lnk rt_main.obj   
### Created: ..\code_gen_example.exe 
### Successfully generated all binary outputs.

8. Now, let's go ahead and run this executable by executing the following command in MATLAB Command Window:

>>  !code_gen_example.exe
** starting the model ** 
Opening Text File 
** created code_gen_example.mat ** 
Closing Text File

This will create the text file myfile.txt in the current directory. This text file will contain the time and output values. To test we are getting the right output and compare the results of generated code to the model run in Simulink, try the following commands:

>> data = csvread('myfile.txt');
>> plot(data(:,1),data(:,2))

The plots might look slightly different because the model uses a random number generator, but you should see a sine wave with added noise similar to the output of Scope block in the model.

            <Output in TXT file when model is run by the generated EXE>

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MATLAB: How to generate an executable file from Simulink which reads data from a binary file to use those values as model block parameters

There are several possible ways to generate code which reads data from a binary file and uses those values as block parameters. One of the easiest ways is to manually include the code to read the binary file in 'ert_main.c' file of the generated code. For its implementation, the block parameters whose values are read from the binary file during execution, need to be declared as Simulink global parameters.

Please find the attached example model 'read_bin.slx' and a binary file 'abc.bin'. This model has a block parameter value 'gain' in the 'Gain' block whose value is supposed to be read from the binary file 'abc.bin' everytime we run the executable file generated from code generation. Please open the attached model and execute the following steps -

1. Create a global parameter 'gain' in the MATLAB Workspace by entering the following commands in the MATLAB Command Window:

>> gain = Simulink.Parameter; 
>> gain.Value = 0;  %initialize the value 
>> gain.CoderInfo.StorageClass = 'SimulinkGlobal';  %change the storage class to global

2. Generate code and the executable file by building the model using Ctrl+B.

3. Navigate to, and open the generated code file 'ert_main.c' in the folder 'read_bin_ert_rtw'.

4. Include the following code inside the main function 'int_T main(int_T argc, const char *argv[])', in the 'ert_main.c' file:

/* Open file for reading */
FILE *f; 
f = fopen("abc.bin", "rb");
fread(&read_bin_P.gain, 1,sizeof(double),f); 
printf("gain is %lf",read_bin_P.gain);
fclose(f);

5. Generate the executable again by executing the following command:

>> !read_bin.bat

6. Make sure to find the new generated executable file 'read_bin.exe' in the Current directory or the Parent directory and have the 'abc.bin' file stored in the same directory. Please run the executable by entering the following command:

>> !read_bin.exe

7. To verify the gain value, load the generated MAT logged file ' read_bin.mat' in MATLAB Workspace, and inspect the values of 'rt_yout'. The output would be 5 times (constant * gain), the value read from the binary file.

8. Modify the value in the binary file by entering the following commands:

>> fid = fopen ('abc.bin', 'w'); 
>> fwrite(fid, 2400, 'double'); 
>> fclose(fid);

9. Repeat steps 6 and 7. The output has changed to 12000 (5* 2400) now.

MATLAB: How to include custom code in the generated initialize function when an initialize block is already present in the model

As a workaround, you can create a wrapper function that includes all of the custom code you would like to execute upon model initialization. In order to include this wrapper function in the generated code, place a MATLAB Function block within the Initialize Function block. Use the "coder.target" and "coder.ceval" commands in the MATLAB Function block to conditionally call the wrapper function when generating code for the model.

For example, the contents of the MATLAB function block would look like the following:

function y = fcn(u)
y=u;
if coder.target('Sfun')
% do nothing during Simulation
else
% call external C code in the generated <model>_initializate function
coder.cinclude('foo.h'); % include custom header files
coder.ceval('foo', 10, 20); % execute custom C code in generated code
end
end

In the generated "<model>.c" file, under the "<model>_initialize" function you would see the following:

void <model>_initialize(void)
{
...
foo(10.0, 20.0);
...
}

In the generated "<model>.h" file you would see the following include directive:

#include foo.h

Best Answer

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MATLAB: How to generate an executable file from Simulink which reads data from a binary file to use those values as model block parameters

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