MATLAB Link for Code Composer Studio Development Tools

Working with Links and Data

With the target code loaded, you can use the MATLAB Link for Code Composer Studio functions to examine and modify data values in the processor.

When you look at the source file listing in the CCS IDE Project view window, there should be a file named ccstut.c. The MATLAB Link for Code Composer Studio ships this file with the tutorial and includes it in the project. ccstut.c has two global data arrays--ddat and idat. They are declared and initialized in lines 10 and 11 of the source code. You access these processor memory arrays from MATLAB using the functions read and write.

The MATLAB Link for Code Composer Studio provides three functions to control target execution--run, halt, and restart. To demonstrate these commands, use CCS IDE to add a breakpoint to line 64 of cctut.c. Line 64 is

• printf("Link for Code Composer: Tutorial - Memory Modified by Matlab!\n");
  

For information about adding breakpoints to a file, refer to your Code Composer Studio User's Guide from Texas Instruments. Then proceed with the tutorial:

1. To demonstrate the new functions, try the following functions.

• halt(cc)                 % Halt the processor
  restart(cc)              % Reset the PC to start of program
  run(cc,'runtohalt',30);  % Wait for program execution to stop at 
                           % breakpoint! (timeout = 30 seconds)
  

1. When you switch to viewing CCS IDE, you see that your program stopped at the breakpoint you inserted on line 64, and the program printed

   • Link for Code Composer: Tutorial - Initialized Memory
     Double Data array = 16.3 -2.13 5.1 11.8
     Integer Data array = 1-508-647-7000
     

   in the CCS IDE Stdout tab. Nothing prints in MATLAB.

2. Before you restart your program (currently stopped at line 64) you can change some of the values in memory. Perform one of the procedures listed below based on your target processor.

1. C5xxx processor family--Type the following functions to demonstrate the read and write functions.
   1. Type ddatv = read(cc,address(cc,'ddat'),'double',4).

   • MATLAB responds with

     ddatv =

     • 
          16.3000   -2.1300    5.1000   11.8000
       

   2. Type idatv = read(cc,address(cc,'idat'),'int16',4).

   • Now MATLAB returns

     idatv =

     1 0 508 0

     Because you requested 16-bit integers, whose maximum value is 512, the values 647 and 7000 come back as zeros since they cannot be represented as 16-bit integers. Using int32 would have returned the full values for all the data in idatv.

   3. You can change the values stored in ddat by typing write(cc,address(cc,'ddat'),double([pi 12.3 exp(-1)...
sin(pi/4)]))

   • The double argument directs MATLAB to write the values to the target as double-precision data.

   4. To change idat, type

   • write(cc,address(cc,'idat'),int32([1:4]))

     Here you write the data to the target as 32-bit integers (convenient for representing phone numbers, for example).

   5. Start the program running again by typing

   • run(cc,'runtohalt',30);

     Checking the Stdout tab in CCS IDE reveals that ddat and idat contain new values. Now we read those new values back into MATLAB.

   6. Type ddatv = read(cc,address(cc,'ddat'),'double',4).

   • ddatv =

     3.1416 12.3000 0.3679 0.7071

     ddatv does contain the values you wrote in step c.

   7. Check that the change to idatv occurred by typing

   • idatv = read(cc,address(cc,'idat'),'int16',4)

     MATLAB returns the new values for idatv.

     idatv =

     1 2 3 4

   0. Finally, use restart to reset the program counter for your program to the beginning. Type

   • restart(cc);

   C6xxx processor family--Type the following commands to demonstrate the read and write functions.

   1. Type ddatv = read(cc,address(cc,'ddat'),'double',4).

   • MATLAB responds with

     ddatv =

     • 
          16.3000   -2.1300    5.1000   11.8000
       

   2. Type idatv = read(cc,address(cc,'idat'),'int16',4).

   • Now MATLAB responds

     idatv =

     1 0 508 0

     Because you requested 16-bit integers, whose maximum value is 512, the values 647 and 7000 come back as zeros since they cannot be represented as 16-bit integers. Using int32 would have returned the full values for all the data in idatv.

   3. You can change the values stored in ddat by typing write(cc,address(cc,'ddat'),double([pi 12.3 exp(-1)...
sin(pi/4)]))

   • The double argument directs MATLAB to write the values to the target as double-precision data.

   4. To change idat, type

   • write(cc,address(cc,'idat'),int32([1:4]))

     Here you write the data to the target as 32-bit integers (convenient for representing phone numbers, for example).

   5. Now start the program running again by typing

   • run(cc,'runtohalt',30);

     Checking the Stdout tab in CCS IDE reveals that ddat and idat contain new values. Now read those new values back into MATLAB.

   6. Type ddatv = read(cc,address(cc,'ddat'),'double',4).

   • ddatv =

     3.1416 12.3000 0.3679 0.7071

     ddatv does contain the values you wrote in step c.

   7. Check that the change to idatv occurred by typing

   • idatv = read(cc,address(cc,'idat'),'int32',4)

     MATLAB returns the new values for idatv.

     idatv =

     1 2 3 4

   0. Finally, use restart to reset the program counter for your program to the beginning. Type

   • restart(cc);

3. The MATLAB Link for Code Composer Studio offers two more functions for reading and writing data to your target. These functions let you read and write data to the processor registers: regread and regwrite. They let you change variable values on the processor in real time. As before, the functions behave slightly differently depending on your target. Select the appropriate procedure for your target to demonstrate regread and regwrite.

1. C5xxx processor family--Most registers are memory-mapped and consequently are available using read and write. However, the PC register is not memory mapped. To access this register, you use the special pair of functions--regread and regwrite. The following commands demonstrate how to use these functions to read and write to the PC register.
   1. To read the value stored in register PC, type

   • cc.regread('PC','binary')

     To tell MATLAB what datatype you are reading, the string binary indicates that the PC register contains a value stored as an unsigned binary integer.

     In response, MATLAB displays

     ans =

     33824

   2. To write a new value to the PC register, type

   • cc.regwrite('PC',hex2dec('100'),'binary')

     This time, binary as an input argument tells MATLAB to write the value to the target as an unsigned binary integer. Notice that you used hex2dec to convert the hexadecimal string to decimal.

   3. Check the PC contains the value you wrote.

   • cc.regread('PC','binary')

   C6xxx processor family--regread and regwrite let you access the processor registers directly. Type the following functions to get data into and out of the A0 and B2 registers on your target.

   1. Retrieve the value in register A0 and store it in a variable in your MATLAB workspace. Type

   • treg = cc.regread('A0','2scomp');

     treg now contains the two's complement representation of the value in A0.

   2. Retrieve the value in register B2 as an unsigned binary integer, by typing

   • cc.regread('B2','binary');

   3. Now, use regwrite to put the value in treg into register A2.

   • cc.regwrite('A2',treg,'2scomp');

     CCS IDE reports that A0, B2, and A2 have the values you expect. Select View->CPU Registers->Core Registers from the CCS IDE menu bar to see a listing of the processor registers.

Loading Files into CCS

Working with Embedded Objects