RE: [avr-gcc-list] Reusing code and variables from bootloader in main program

[Ivan Dimitrov]

you have to put all vars in one structure (or if you use only function pointers you can pack them in array of functions) and place them in the very begging of the RAM. This can be done with dedicated linker section.

Regards I. Dimitrov



> From: address@hidden
> Date: Sun, 27 Jun 2010 00:04:22 +1100
> To: address@hidden
> Subject: [avr-gcc-list] Reusing code and variables from bootloader in main program
>
> I have atmega64 with SD card connected. The card is used for storing
> WAV files, logs, etc. I want to add a bootloader that would upgrade
> the main program if certain file is present on the card. Using
> separate copies of filesystem library in main program and bootloader
> is too expensive in terms of flash space. I am thinking about this
> solution: link the bootloader with filesystem libraries, and in main
> program have a set of pointers to filesystem library functions in
> .noinit section. When bootloader is started , it upgrades main program
> if necessary, and then initializes the prointers with correct
> addresses and jumps to address zero, starting the main program. Since
> variables are in .noinit, main program would not initialize them,
> preserving the addresses. Obviously, main program also needs to know
> addresses of all global variables used by filesystem lib. The problem
> is : how do I make both program use same addresses for certain
> variables?
>
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