This Optiboot version is modified to add the capability of reflashing from an external SPI flash memory chip. As configured this will work with Moteino (www.lowpowerlab.com/Moteino) provided a SPI flash chip is present on the dedicated onboard footprint. Summary of how this Optiboot version works:
- it looks for an external flash chip
- if one is found (SPI returns valid data) it will further look for a new sketch flash image signature and size starting at address 0: FLXIMG:9999:XXXXXXXXXXX where: - 'FLXIMG' is fixed signature indicating FLASH chip contains a valid new flash image to be burned - '9999' are 4 size bytes indicating how long the new flash image is (how many bytes to read) - 'XXXXXX' are the de-hexified bytes of the flash pages to be burned - ':' colons have fixed positions (delimiters)
- if no valid signature/size are found, it will skip and function as it normally would (listen to STK500 protocol on serial port)
The added code will result in a compiled size of just under 1kb (Originally Optiboot takes just under 0.5kb)
To compile copy the Optiboot.c and Makefile files where Optiboot is originally located, mine is at:
Backup the original files andbefore overwrite both files. Then compile by running: make atmega328 make atmega1284p
##License GPL 3.0. See License.txt file.