Programming the Dwengo board without a programmer

Posted Sat, 2010-07-24 15:57 by Sean

Installing the bootloader

Programming the bootloader on the Dwengo board can be done easily. For this you first download the hex file Dwengo bootloader that is attached to this page. This hex file contains the bootloader for the Dwengo board. With MPLAB you can program the Dwengo board with this hex file. The bootloader will now take the first 8192 bytes (0x0000 - 0x1FFF) of the program memory.

Writing a program

Since the bootloader takes the first 8192 bytes (0x0000-0x1FFF) of program memory, you have to take two things into account when writing your own programs: remapping the interrupt vectors and adjusting the linker script.

Remapping the interrupt routines is done with the following code:

  1. void YourHighPriorityISRCode();
  2. void YourLowPriorityISRCode();
  3.  
  4. // vector remapping
  5.  
  6. // Bootloader occupies addresses 0x000-0x1FFF and thus cannot be used.
  7. // Thus adresses 0x00, 0x08 and 0x18 (used for reset, high prior interrupt,
  8. // and low prior interrupt) have to be remapped.
  9. extern void _startup(void);
  10. #pragma code REMAPPED_RESET_VECTOR = 0x2000
  11. void _reset(void) {
  12.     _asm goto _startup _endasm
  13. }
  14.  
  15. #pragma code REMAPPED_HIGH_INTERRUPT_VECTOR = 0x2008
  16. void Remapped_High_ISR(void) {
  17.      _asm goto YourHighPriorityISRCode _endasm
  18. }
  19. #pragma code REMAPPED_LOW_INTERRUPT_VECTOR = 0x2018
  20. void Remapped_Low_ISR (void)
  21. {
  22.      _asm goto YourLowPriorityISRCode _endasm
  23. }
  24.  
  25. #pragma code HIGH_INTERRUPT_VECTOR = 0x08
  26. void High_ISR(void) {
  27.      _asm goto 0x2008 _endasm
  28. }
  29. #pragma code LOW_INTERRUPT_VECTOR = 0x18
  30. void Low_ISR(void) {
  31.      _asm goto 0x2018 _endasm
  32. }
  33.  
  34. #pragma code
  35.  
  36. // Interrupt handler routines
  37. #pragma interrupt YourHighPriorityISRCode
  38. void YourHighPriorityISRCode() {
  39.   //Check which interrupt flag caused the interrupt
  40.   //Service the interrupt
  41.     //Clear the interrupt flag
  42. }
  43. #pragma interruptlow YourLowPriorityISRCode
  44. void YourLowPriorityISRCode() {
  45.   // Check which interrupt flag caused the interrupt
  46.  // Service the interrupt
  47.    // Clear the interrupt flag
  48. }

The linker script has to be adjusted in such a way the a piece of the program memory is reserved for the bootloader. Moreover, there also needs to be reserved a piece of memory for the interrupt vectors. The following lines describe a working linker script that can be used with the bootloader:

  1. LIBPATH .
  2.  
  3. FILES c018i.o
  4. FILES clib.lib
  5. FILES p18f4550.lib
  6.  
  7. CODEPAGE   NAME=bootloader START=0x0               END=0x1FFF         PROTECTED
  8. CODEPAGE   NAME=vectors    START=0x2000            END=0x2029         PROTECTED
  9. CODEPAGE   NAME=page       START=0x202A            END=0x7FFF
  10. CODEPAGE   NAME=idlocs     START=0x200000          END=0x200007       PROTECTED
  11. CODEPAGE   NAME=config     START=0x300000          END=0x30000D       PROTECTED
  12. CODEPAGE   NAME=devid      START=0x3FFFFE          END=0x3FFFFF       PROTECTED
  13. CODEPAGE   NAME=eedata     START=0xF00000          END=0xF000FF       PROTECTED
  14.  
  15. ACCESSBANK NAME=accessram  START=0x0            END=0x5F
  16. DATABANK   NAME=gpr0       START=0x60           END=0xFF
  17. DATABANK   NAME=gpr1       START=0x100          END=0x1FF
  18. DATABANK   NAME=gpr2       START=0x200          END=0x2FF
  19. DATABANK   NAME=gpr3       START=0x300          END=0x3FF
  20. DATABANK   NAME=usb4       START=0x400          END=0x4FF          PROTECTED
  21. DATABANK   NAME=usb5       START=0x500          END=0x5FF          PROTECTED
  22. DATABANK   NAME=usb6       START=0x600          END=0x6FF          PROTECTED
  23. DATABANK   NAME=usb7       START=0x700          END=0x7FF          PROTECTED
  24. ACCESSBANK NAME=accesssfr  START=0xF60          END=0xFFF          PROTECTED
  25.  
  26. SECTION    NAME=CONFIG     ROM=config
  27.  
  28. STACK SIZE=0x100 RAM=gpr3
  29.  
  30. SECTION       NAME=USB_VARS   RAM=usb4

Programming without a programmer

When the program is ready and you have generated a hex file, you can program the Dwengo board. First you have to download the USB framework from the Microchip website External link. Install this framework and under C:\Microchip Solutions\USB Device - Bootloaders\HID - Bootloader you can find the program HIDBootLoader.exe. Start this program. If the program does not want to start, you also have to install the Microsoft .NET framework External link.

After this connect the Dwengo board to your computer with a USB cable (without the programmer). Next reset the Dwengo board while pressing the C button. When you release the C button, the board is bootloader modus. The Dwengo board will now be detected by the HIDBootLoader program. With this HIDBootLoader program you can load you hex file and program it on the Dwengo board.