If I wanted to do a bootloader on a PIC24 - what choices?

[JamesW]

Hi Folks,

Hypothetical question. I've got a PIC24 in a system running great, and doing just what I need it to. It's connected via a modem to a web server that we've also created and all is hunky dory.

If I wanted to add to the system the ability to reprogram the processor remotely, what options do I have?

I do have a spare EEPROM space on the board - where potentially I could fit a 1Mbit I2C eeprom - if that is an option, although there is always the phobia of it not copying across the code right and failing.

Don't mind changing the board, don't mind adding a 2nd processor to do it.

Needs to be pretty bullet proof though.

Ideas on a postcard please.

Thanks

James

[newguy]

Bootloader: http://www.smallridge.com.au/ (why reinvent the wheel?)

Very satisfied customer of Andrew's SD card driver. If I had a need for an ethernet bootloader, Andrew would be the first person to whom I would turn.

On a side note, my present employer is facing the same issues and questions you are presently contemplatiing. We're leaning toward a 1Mb SPI EEPROM with extra overhead code running in the main application to do a rigorous check on any new image. We are also looking at a mechanism to keep not only the new image but also the last image. In that manner, if there is something very obviously wrong with the new image, at least the end user can force it to revert to the previous image.

[Ttelmah]

Newguy makes the critical point. "rigorous check on any new image".
At the end of the day you can do a bootloader in protected memory space on the PIC24. Have it load from the EEPROM. Then have extra code in your "main" that reads the file, and does checksum and validity checks on this before storing this, and setting a bit to signal to the bootloader code to actually perform the programming.
You can do exactly the same with an external PIC, which then programs the main chip.
In both cases the bootloader/programming code looks for a flag in the EEPROM to perform the programming. This is only set once you have verified the code is correct.

[asmallri]