Trevor's Electonics Blog

Hi again. Onto the next example, this time on page 295 (figure 8.28). The code for this one is called ‘ledtoggle_nofsm’ and it’s in the chap8 folder.

Now that we’ve defined EXPLORER16_100P in the pic24_all.h file, here is a new checklist to use:

1. Double click on the project file for the exercise your wanting to do. (Make sure you don’t already have MPLAB open or it will complain)
2. Set the processor type in the menu item Configure – Select Device. The default PIC24 that comes with the Explorer16 is PIC24FJ128GA010.
3. Remove the linker script from the workspace files viewer under “Linker Scripts” (don’t add anything, MPLAB will manage it for you)
4. Change from DEBUG to RELEASE in the drop down at top of MPLAB screen
5. Select your programmer (Programmer – Select Programmer). I use the ICD2
6. Make required changes to the code (see below for this exercise)
7. CTRL-F10 to build all
8. When you get the BUILD SUCCEDED message, program the chip (Programmer – Program)
9. Click ok the the ICDWarn0046 warning (unless you’ve got sick of this message and clicked the “don’t show me again” like I did)
10. disconnect the ICD2 when the programmer has completed.

Here is the modification needed for this one to work. Shown here is the code between the #include directive and the start of the main() function.

You should see the very left LED blinking. When you press the right of the 4 buttons, the second from left LED should toggle (light up if it’s the first press). Keep pressing and releasing and observe what happens. You will notice the LED state doesn’t change until the button is released.

#include "pic24_all.h"

/** \file
A program that toggles an LED whenever a pushbutton switch is pressed
and released. Does not use a finite statement approach.
*/

#if defined(EXPLORER16_100P)

/// LED1
#define CONFIG_LED1() CONFIG_RA6_AS_DIG_OUTPUT()
#define LED1  _LATA6    //_LATA6 is port register for RA6
#warning Were using the explorer16 version of the code
/// Switch1 configuration
inline void CONFIG_SW1()  {
  CONFIG_RD13_AS_DIG_INPUT();     //use RD13 for switch input
  ENABLE_RD13_PULLUP();           //enable the pullup 
}
#define SW1              _RD13       //switch state

#else  // not Explorer16

/// LED1
#define CONFIG_LED1() CONFIG_RB14_AS_DIG_OUTPUT()
#define LED1  _LATB14     //led1 state
#warning If your using an Explorer16, this program wont work
/// Switch1 configuration
inline void CONFIG_SW1()  {
  CONFIG_RB13_AS_DIG_INPUT();     //use RB13 for switch input
  ENABLE_RB13_PULLUP();           //enable the pullup 
}
#define SW1              _RB13       //switch state

#endif  // if defined EXPLORER16_100P

#define SW1_PRESSED()   SW1==0  //switch test
#define SW1_RELEASED()  SW1==1  //switch test

int main (void) {
.....

Example 7 which is Figure 8.30 on page 298 is called ledtoggle and is in the chap8 folder. It’s the same changes as example 6 above except the original code has some extra bits that example 6 didn’t have.

#include "pic24_all.h"

/** \file
A program that uses a finite state machine approach for
toggling an LED whenever a pushbutton switch is pressed
and released. Demonstrates the use of debounce delays when
polling a switch input.
*/

#if defined(EXPLORER16_100P)

/// LED1
#define CONFIG_LED1() CONFIG_RA6_AS_DIG_OUTPUT()
#define LED1  _LATA6    //_LATA6 is port register for RA6
#warning Were using the explorer16 version of the code

/// Switch1 configuration
inline void CONFIG_SW1()  {
  CONFIG_RD13_AS_DIG_INPUT();     //use RD13 for switch input
  ENABLE_RD13_PULLUP();           //enable the pullup
}
#define SW1              _RD13       //switch state

#else  // not Explorer16

/// LED1
#define CONFIG_LED1() CONFIG_RB14_AS_DIG_OUTPUT()
#define LED1  _LATB14     //led1 state
#warning If your using an Explorer16, this program wont work

/// Switch1 configuration
inline void CONFIG_SW1()  {
  CONFIG_RB13_AS_DIG_INPUT();     //use RB13 for switch input
  ENABLE_RB13_PULLUP();           //enable the pullup
}
#define SW1              _RB13       //switch state

#endif  // if defined EXPLORER16_100P

#define SW1_PRESSED()   SW1==0  //switch test
#define SW1_RELEASED()  SW1==1  //switch test

typedef enum  {
.....

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.