Re: [avr-libc-dev] Problem writing to flash - atmega644

[Brian Sidebotham]

> I am using the boot_program_page routine taken 'verbatim' from the
> avrlibc docs:
> http://www.nongnu.org/avr-libc/user-manual/group__avr__boot.html#g7249d1
> 2e06789cd306583abf7def8176
>
> I would expect the following code to blank all of flash. Yet it doesn't
> happen, since the routine completes and returns as if nothing had
> happened. The application runs perfectly after reset/reboot.
>
> --------------------
>
> void  __attribute__((section (".bootloader"))) CopyMemory(void){
>
>     int i;
>     char buffer[ 256 ];
>
>     memset( buffer , '\0' , 256 );
>     for( i=0 ; i<256 ; i++ ){
>         boot_program_page( i , buffer );
>     }

I struck this same problem when I first used these functions, and I think there 
is a case for adding a note in the documentation for this example.

If you look carefully at the definition of boot_program_page(uint32_t page, 
uint8_t *buf) you'll notice that page is of type uint32_t - clue number one!

The second clue is the boot_page_erase(page); line in the example of 
boot_program_page, because the definition of boot_page_erase(...) is
#define boot_page_erase(address) __boot_page_erase_normal(address)

The important thing is that where page has been used as a variable name in the 
example, it should really be address, or page_address. You do not pass the page 
number to the function, but an address contained within the page.

instead, something like the following

int i;
#define FLASH_PROGRAM_SIZE 32768
...
for (i=0; i<FLASH_PROGRAM_SIZE; i+= SPM_PAGESIZE)
   boot_program_page(i);
...

Best Regards,

Brian Sidebotham.