Features: Available under the GPL license Supports PIC16F87xA parts (block writes to flash ROM) and the older non-A parts 4K word parts not yet tested, but only EEPROM support differs from 8K word version Requires no space in bank 0 User program has immediate control at power-on and after resets Uses read-write-verify sequence to minimize writes Uses the USART on the PIC and no other pins Robust error handling Supports program flash ROM and data EEPROM (optional) Reports the address range used by the bootloader to detect an overlap of the program to write and the bootloader (the bootloader still checks addresses to prevent writting over itself) Allows for updating the bootloader on 8K word parts -- use a bootloader in bank 1 to write another in bank 3, or vise versa Written mostly in C (CCS PIC C compiler) Depending on options, requires between 316 and 340 instructions Command line uploader available in C for POSIX compliant systems (has been compiled with gcc on Linux and Windows)

* Updated 2003-3-18

Configurable options:

• USART data rate control values (works)
• Timeout delay for a request to upload new code; default is 0.5s (works)
• Ability to write EEPROM (works)
• A program address range to not update (used to prevent overwritting the bootloader; works)
• Use pullups on port B (made the bootloader smaller); default is no (untested)
• 4K or 8K word versions to support the different memory models (8K works, 4K untested)

Requirements

• A midrange PIC (the ones that use 14-bit words).
• A PIC with support for self-programming.
• A PIC that maps the upper 16 bytes of RAM in banks 0 and 2 to the same file registers.
• A PIC with an USART.
• A disabled WDT (no support for them yet).
• Should work with all PIC16F87x and PIC16F87xA parts.

Files

Ready to use bootloaders in Intel HEX files

If a configuration is not present here, it is because I didn't bother to make it, not because the configuration won't work. However, I have not tested every possible configuration. I did test the individual options, save for the 4K word parts, that can be matched together for a specific configuration, so I think these bootloaders will work. I have been wrong before, though. The 4K word part versions only differ in their EEPROM support, so any bootloader for 4K word parts that lack EEPROM support should work.

There is no distinction between 28 and 40 pin parts because the only I/O is through the USART so the code is identical.

Usage from PIC software

1. Compile justBootloader.c modified to provide the settings you require, or use one of the pre-compiled bootloaders given on this site.
2. Load the compiled result onto the PIC to you want to use.
3. Write and compile your own program without the bootloader. Take these factors into consideration:
   • The bootloader will change values in memory with no regard to what your program uses the memory for. Addresses in bank 0 above 0x55 and address 0x75 in bank 3 (4K parts only) are used by the bootloader.
   • The bootloader will globally disable interrupts and will use timer 0.
   • If the bootloader does not initialize the USART, your code will need to perform the initalization prior to calling the bootloader.
   • Avoid using the bootloader's address space. It will not write new code over itself. With the CCS PIC C compiler, add some code like this:
     // do not use the bootloader's address space
#ORG 0x1800, 0x193B { }
4. Your program will have to call the bootloader. The following code are examples for calling the bootloader; you'll need to modify them to meet your needs. Specifically, the entry address of the bootloader (listed under Bootloader location in the table above) will need to be set correctly, and changes will be needed when making the call outside of bank 0.

   C	Assembly
   /**  * Calls the bootloader's main function.  */ void BB_main() {    #bit romBank0 = 0xA.3    #bit romBank1 = 0xA.4    #asm    // select program bank 3    bsf romBank0    bsf romBank1    // call the bootloader at 0x1867    call 0x67    // select program bank 0    bcf romBank0    bcf romBank1    #endasm }	;Calls the bootloader's main function. BSF 0A.3 ; select program bank 3 BSF 0A.4 CALL 67 ; call the bootloader BCF 0A.3 ; select program bank 0 BCF 0A.4

5. To update the bootloader using an existing bootloader, write a new bootloader to a different address space. For example, use a bootloader stored in bank 3 to write a new one in bank 1. Be sure to change the way the bootloader is called, too.

Protocol

Other questions