Re: [avr-gcc-list] bootloader: replace bootloader with a new bootloader

[E. Weddington]

Joerg Wunsch wrote:

> Torsten Mohr <address@hidden> wrote:
>  
>
> Basically, if you want to do this, you need a bootloader that is small
> enough so two bootloaders will fit into the boot region.  That way, it
> should be possible to reprogram the inactive half of the bootloader.
> Take care to understand all the implications of programming the
> No-read-while-write (NRWW) section of the flash ROM.  As soon as your
> new half of the bootloader has been programmed successfully (and
> verified CRC or such), flip the first page of the bootloader area to
> point to the new loader.
>  

Something similar to this, is to have your bootloader be half or less 
than the availble bootloader area. Then, when calling the bootloader 
(which resides in the lower half of the bootloader section), the first 
thing the bootloader does is to copy itself to the upper half of the 
bootloader area, then call the bootloader copy in the upper half which 
then does the actual bootloading. The bootloading will then write new 
code from the beginning of flash all the way through the first half of 
the bootloader section, hence replacing the bootloader. Granted, if 
there is a power failure then all could be lost. And, yes, this scheme 
actually does work.

Eric