[En-Nut-Discussion] Fwd: RE: Reprogramming

[Ole Reinhardt]

Hi Peter,

normaly you would write some kind of bootloader which will stay resident
in the bootloader area of you AVR which are the last few pages of flash.
You can define the size of this bootloader area by setting the fuse bits
accordingly.

There are several application notes for different types of bootloaders.
At least you can use eboot.

> From what I can gather, I can use the eboot code from the egnite
>  website and flash it into lower flash. Then flash my code normally,
>  but disabling the flash erase first. Once done, the bootloader is in
>  lower flash and my code is in upper flash.  I cannot figure how to do

I don't understand why you want you bootloader in the lower flash. By
enabling the bootloader with the fuse bits, the bootloader will be
executed always first and has to decide if it loads a new application or
jumps into the existing code.

So you can easily use an I/O pin or a value in the eeprom to check if
you want to upgrade you application.

> 1. Write a resident loader and the needed functionality to receive the
>  new software, and write it (somehow) into flash memory.  

That's exactly what you'll have to do. Write it into the AVR bootloader
section. Write your own code or reuse eboot.

Bye,

Ole

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