Lab EE475 #2
Fall 2008
Creating C Programs With the CodeWarrior IDE In this lab you will use the Metrowerks CodeWarrior compiler to create, build, and run several simple C programs. CodeWarrior is a code development environment that supports a wide variety of processor targets, including the HC08 and HC12. We will be using it with the MC9S12C32 processors on the Axiom MCU Project Boards in the lab.
Logging On:
1. Wake up the computer (or turn on the power if it is off). 2. Begin by pressing Ctrl+Alt+Delete (Windows XP). 3. Enter your username and password, and select the proper domain.
Launching :
Start the development application: > Programs | Freescale CodeWarrior | CW for HC12 V4.5 | CodeWarrior IDE
Setting up the CodeWarrior software project:
1. From the CodeWarrior File menu, select the New option. The New Project window should appear. 2. Fill in a project name (e.g., Lab2xyz, where xyz are your initials), and use the Set button to locate a subdirectory you can read and write: Your Z: drive is a good choice. Choose the HC(S)12 New Project Wizard and press OK. 3. Using the Wizard prompts: a. b. c. d. e. f. g. h. Select the MC9S12C32 derivative Select C language support No Processor Expert No PC-lint support Yes ANSI Startup Code No floating point support Small memory model Check the boxes to select Full Chip Simulator AND P&E Multilink/Cyclone Pro
and then press Finish. The project framework has now been created. In the left pane, open all the file browse folders by pressing the "+" boxes to see all the supporting files. Also, make sure that P&E ICD is the target selected in the drop-down box at the top of the folders pane.
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Compiling a simple program:
Using the browse view, locate the main.c file in the Sources group. Double-click to launch the file in an editor window. This dummy main() routine just enables interrupts and then traps itself in an infinite loop. Keep in mind that embedded software generally does not "return" to a calling routine, so an infinite loop somewhere in the code is not unusual. Now replace the main() routine with the following:
void main(void) { /* This is a test program. * The results are meaningless. */ int j; volatile int val; val=10; for(j=0;j<6;++j){ val=val+j; } for(;;); /* endless loop */ }
Note that volatile int is used to prevent the compiler from eliminating the "useless" code involving val. Also, note that the _asm() function can be used to insert an in-line assembly language instruction, such as _asm("nop"); Save the main.c file, then select Make from the Project menu (or press the "make" icon on the task bar). Any compiler errors will appear in a pop-up window. Ask for help if any of the preliminary steps did not work properly. Once the program compiles correctly, try making some deliberate errors (missing semicolons, misspelled variable names, etc.) and see what the compiler errors look like.
Connecting to the SLK board
Carefully connect the USB cable between the computer and the shiny USB receptacle on the edge of the SLK board opposite to the microcontroller daughterboard. The USB power LED should turn on, and the VDD LED on the microcontroller daughterboard should light up. Seek help if the board does not power up as expected.
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Debugging the program
After the program compiles and links correctly, press the green Debug icon to launch the simulator/debugger application. The debugger app automatically opens a variety of windows to show the source code, disassembly, register contents, etc. You may get a warning message indicating that the non-volatile memory on the chip will be erased: this is OK. The LEDs on the daughterboard should turn off, except for the green power LED. The Debugger app should show a bunch of windows, including the source code of your main.c, the current contents of the processor registers, a disassembly of the instructions, and some memory and data viewing windows (see below).
In the debugger, press the green arrow ( , start/continue) to run the program using the debugger. After a few seconds, press the red ( , stop) button. Observe the updated views in each window. Now go to the Source window in the debugger and scroll until you can see the val=10; line. Set a breakpoint on this line by pointing with the mouse, doing a rightclick to bring up the context menu, and selecting "Set Breakpoint". A red arrow should appear on that line in the Source window.
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Select Restart in the Run menu, and observe that the simulator restarts the code and stops at the breakpoint line. Now use the Single Step button to go through the program one line at a time. Things to keep in mind: 1. Each line of the C program usually executes several assembly language instructions. Observe the assembly instructions in the Assembly window. Note that you can use the Assembly Step button to execute the machine instructions one by one. 2. The variables are updated in the Data window after each step. 3. The compiler generates special startup and initialization code that is executed before turning control over to your main() routine. To see this, select Reset from the ICD-12 menu, then start single stepping the program until you reach your main() routine. What is the startup and initialization code for?
Running the software simulator
In addition to the hardware debugging connection, the CodeWarrior debugger app can also perform a simulation of the chip (no hardware required). Setup the following: 1. Close the debug app (True-Time) and return to the CodeWarrior project. 2. In the drop-down box at the top of the project file pane, select Simulator instead P&E of ICD. 3. Recompile and link your program. 4. Now re-launch the debugger app (green bug arrow). Try running the code, setting breakpoints, etc., using the simulator.
Problems to do in the lab:
For the following lab problems you need to demonstrate a working program to get credit for it. Have the instructor initial the verification sheet for each working assignment that is completed. Problem #1: (BE SURE TO SWITCH BACK TO USING THE P&E ICD HARDWARE DEBUGGING) (a) Add sizeof() expressions to your main() program so that you can determine the byte sizes used for the types examined last week in Lab #1:
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char signed char short int long int double
unsigned char short int float
One way to do this is to assign the result to a variable, then single-step the program to see each result, e.g., val=sizeof(char); val=sizeof(unsigned char); val=sizeof(short); (b) Determine if the HC12 storage is little endian or big endian by saving an integer value in your program and then observing the storage using the Memory window. (c) Next, observe what happens if you remove or comment-out the endless loop at the end of your program ( for(;;); ). Do a single-step and see what the Assembly window shows. (d) Finally, observe what happens if you change the declaration volatile int val; to just int val; Recompile the program and single-step it through the code. What did the compiler do differently this time? Explain. Demonstrate your program and results for the instructor. Before moving on to Problem #2, keep a copy of the Problem #1 main.c file using the following procedure: First, re-edit the file so that it has the volatile int val declaration and the infinite loop at the end. In the CodeWarrior window, save the main.c file under the name (Save As) main1.c, then right-click on the file name in the project browser and remove it from the Sources folder. Don't be alarmed by the warning message: the file itself will not be deleted from the disk folder, only from the list of project files. Next, add the main.c file back into the Sources group, open it in the editor, and delete the statements within the main() routine. Re-save the main.c file, then go ahead with the next problem.
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Problem #2: Create a C program that blinks the two LEDs on the microcontroller board. Write the code as a continuous loopyou might want to include a delay (donothing software loop) to make each blink last longer. To implement this program you will need to realize that: (a) The mc9s12c32.h header file includes C definitions of the various processor I/O ports (PORTA, PORTP, etc.) and the individual register bits. (b) The bits in each register are numbered from zero (least significant bit) through seven (most significant bit). (c) The Bit 0 (zero) of Port A (PORTA, 0x0000) is connected to the cathode of LED1. Set the Port A data direction register (DDRA, 0x0002) so that bit 0 is an output. (d) The bit 4 of Port B (PORTB, 0x0001) is connected to the cathode of LED2. Set the Port B data direction register (DDRB, 0x0003) so that bit 4 is an output. (e) Locate the system copy of mc9s12c32.h in order to see all the defined values. The include files should be somewhere like:
C:\Program Files\Metrowerks\CodeWarrior CW12_V3.1\lib\HC12c\include
Put statements in the main() routine in order to implement the flashing LEDs. A partial skeleton is shown below:
void main(void) { /* Set ...