Microcontrollers: From Assembly Language to C Using the PIC24 Family – Chapter 8 Example 2

Continuing with Chapter 8, the next file is the one referred to in Figure 8:5 Improved code example for flashing LED. It takes the previous one and modifies it using macro’s. Well we sort of used macros in the last one to break out the Explorer 16 version and the original. This file is called ledflash and it’s also in the chapter 8 folder.

You will see what the author had in mind. The use of macro’s certainly makes it easier to see what is going on. Here is the modified code that enables the Explorer 16 to run this. Don’t forget to define EXPLORER16_100P.

#if defined(EXPLORER16_100P)
#define CONFIG_LED1() CONFIG_RA6_AS_DIG_OUTPUT()
#define LED1 _LATA6 //_LATA6 is port register for RA6
#warning Were using the explorer16
#else // not Explorer16
#define CONFIG_LED1() CONFIG_RB15_AS_DIG_OD_OUTPUT()
#define LED1 _LATB15 //_LATB15 is port register for RB15
#warning Were not using the explorer16 because EXPLORER16_100P not defined
#endif // if defined EXPLORER16_100P

int main(void) {
    configClock();
    /********** GPIO config **********/
    CONFIG_LED1();
    LED1 = 0;
    while (1) {
        DELAY_MS(250); //delay long enough to see LED blink
        LED1 = !LED1; // Toggle LED
    } // end while (1)
}

This time all the configuration changes needed are done in the short macro section while leaving the actual code identical effectively creating a hardware abstraction layer between the code and the hardware.

Ok so now time to build. Here is a check list to follow for these examples.

1. Define EXPLORER16_100P (Project – Build Options – Project. Then the MPLAB C30 tab. Add the preprocessor macro.
2. Remove the linker script from the workspace files viewer under “Linker Scripts” (dont add anything, MPLAB will manage it for you)
3. Change from DEBUG to RELEASE in the drop down at top of MPLAB screen
4. Select your programmer (Programmer – Select Programmer). I use the ICD2
5. CTRL-F10 to build all
6. When you get the BUILD SUCCEDED message, program the chip (Programmer – Program)
7. Click ok the the ICDWarn0046 warning
8. disconnect the ICD2 when the programmer has completed.

You should now see the LED connected to RA6 (second from left) flash at about 1 per second.

One thing I do want to point out, I am not going to teach you about programming and the PIC etc. The intent of this blog is share my adventures and if you happen to learn something from that, well that’s good. The other thing I’m going to recommend is to buy the book referred to here. See the books web site here. This is also the web site where you will find all the original code the book discusses and what I refer to here.