2 <avr/boot.h>: Bootloader Support Utilities

The macros in this module provide a C language interface to the bootloader support functionality of certain AVR processors. These macros are designed to work with all sizes of flash memory.

Global interrupts are not automatically disabled for these macros. It is left up to the programmer to do this. See the code example below. Also see the processor datasheet for caveats on having global interrupts enabled during writing of the Flash.

Note:

Not all AVR processors provide bootloader support. See your processor datasheet to see if it provides bootloader support.

API Usage Example

The following code shows typical usage of the boot API.

    #include <inttypes.h>
    #include <avr/interrupt.h>
    #include <avr/pgmspace.h>
    
    void boot_program_page (uint32_t page, uint8_t *buf)
    {
        uint16_t i;
        uint8_t sreg;

        // Disable interrupts.

        sreg = SREG;
        cli();
    
        eeprom_busy_wait ();

        boot_page_erase (page);
        boot_spm_busy_wait ();      // Wait until the memory is erased.

        for (i=0; i<SPM_PAGESIZE; i+=2)
        {
            // Set up little-endian word.

            uint16_t w = *buf++;
            w += (*buf++) << 8;
        
            boot_page_fill (page + i, w);
        }

        boot_page_write (page);     // Store buffer in flash page.
        boot_spm_busy_wait();       // Wait until the memory is written.

        // Reenable RWW-section again. We need this if we want to jump back
        // to the application after bootloading.

        boot_rww_enable ();

        // Re-enable interrupts (if they were ever enabled).

        SREG = sreg;
    }