Em 25/3/2011 13:27, Olin Lathrop escreveu:
> Isaac Marino Bavaresco wrote:
>> The boot-loader is not yet finished but I did some tests in the real
>> hardware today, and they show that the word-programming works.
> I have done bootloaders for dsPIC parts.  These have to erase a whole era=
se
> block at a time.  My bootloaders then write whole write blocks within eac=
h
> erase block.  So far that seems to have worked without incident.  I don't
> see why a bootloader would want to write individual words.
>
> I think that could wear out the flash faster too.  It's possible that eac=
h
> word write effects the whole write block.  If a write block is 32 words i=
n
> size, then writing each word individually may stress the flash as if the
> whole block were written 32 times.  I don't know if this is true, but I c=
an
> certainly see how it could be.
>
> Again, word writes don't make much sense for a bootloader.


This is a different boot-loader, it is for a client's existing board,
which I didn't design. It first receives all the firmware, then checks
the firmware for errors (CRC) and finally program it to the FLASH memory.

The application is wireless-connected with intermittent availability (a
few minutes each hour), and the application cannot be stopped for too long.

The board has external FLASH, but just a moderate amount, so I couldn't
use it to buffer the firmware. Luckily, the client's application uses
only a small fraction of the PIC's FLASH, so I decided to use half of
the program memory to store the firmware as it is being received.


My boot-loader inter-operates with the application. When the application
receives packets that are for the boot-loader, it calls a function
inside the boot-loader which saves the packet. When the boot-loader
receives the last packet and validates the firmware, it doesn't return
to the application and do the real programming.

I use word-writes to register in an array of words what blocks were
already received. The blocks may be received in any order and there is a
mechanism to tell the server what blocks are still needed.


Best regards,

Isaac

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