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

[Patrick Mahoney]

Good morning Brian,

Thanks for getting back to me.

It is true that my code snippet was iterating over a page number whereas
the required parameter is the full address.

But still... Erasing the page containing address 0 should blank the
first 256 bytes in memory, which contain the reset vector and the
interrupt vector table. The processor should NOT be functional after
such an operation.

Also, I tried using your code snippet as is and didn't work either. I
even tried:
        for (i=0; i<FLASH_PROGRAM_SIZE; i++)
            boot_program_page(i);
... without anymore success.

As I mentioned yesterday, doing a boot_page_erase_safe(i) within the
previous loop gets executed way too fast. The spm instruction must be
aborting early for some reason...

Best regards,


Pat



-----Original Message-----
From: address@hidden
[mailto:address@hidden On
Behalf Of Brian Sidebotham
Sent: August 21, 2007 10:09 AM
To: Patrick Mahoney
Cc: address@hidden
Subject: Re: [avr-libc-dev] Problem writing to flash - atmega644

> 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.




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