SD card bootloader for atmega processors

As easy as it can get! I spent days with this. Hopefully you wont!

• for any ATMega with 4096kb Bootloader
• uses Petit FatFs R0.03 for FAT12, FAT16, FAT32
• looks for FIRMWARE.BIN and flashes it nearly instantly
• without any interference to your application
• no CRC Check and no version bytes in EEPROM (see KISS)

avr_boot is integrated in Arduino IDE version 1.6.4 or greater!!! See here for instructions.

This is with avr-gcc and avrdude under linux with an Atmega1284p and AVRISP mkII! Adaption to your case (WinAvr, another Atmega, another flash-tool) will not be complicated...

• adapt Makefile
  • MCU_TARGET: Your atmegaXXX
  • BOOT_ADR: in bytes not words!
  • F_CPU: CPU Frequency (not critical. A higher value will work as well)
  • SD_CS_PORT: Data Register of the SD CS pin(see the datasheet for your microcontroller)
  • SD_CS_DDR: Data Direction Register of the SD CS pin
  • SD_CS_BIT: Bit of the SD CS pin
  • USE_LED: For debugging 0...deactivate or 1...active
  • USE_UART: For debugging 0...deactivate or divider (UBRR) for baudate see http://wormfood.net/avrbaudcalc.php
• update spi_pins.h with the SPI pins of your microcontroller if not already defined
• if using USE_LED adapt LED-pins in asmfunc.S
• if you want to add FAT12 adapt pff/src/pffconfh.h (default ist FAT16 + FAT32)
• if you want to support lower case filenames adapt pff/src/pffconfh.h (default is uppercase)
• if you prefer another filename instead of FIRMWARE.BIN adapt main.c
• make (you may need to do "sudo apt-get install avr-libc gcc-avr")
• set fuses: avrdude -c avrispmkII -p m1284p -U hfuse:w:0xda:m
  • find high fuse in http://eleccelerator.com/fusecalc/fusecalc.php?chip=atmega1284p
• flash: avrdude -c avrispmkII -p m1284p -Uflash:w:./avr_boot.hex:i -Ulock:w:0x3F:m

• in Arduino IDE go to File > Preferences and check "Show verbose output during compiliation"
• compile sketch and find the location of your /tmp/buildxxx/sketch.cpp.hex
• make bin file: avr-objcopy -I ihex -O binary sketch.cpp.hex FIRMWARE.BIN
• copy the file into the root of an SD (FAT16/FAT32)
• put it into the SD slot of your ATmega
• reset it
• it might already have happend!

Compiled under linux for atmega328p / atmega1284p

• 3674 / 3724 bytes
• 3984 / 4034 bytes debugging with USE_LED
• 3992 / 4052 bytes debugging with USE_UART

• ATmega168
• ATmega328P
• ATmega32u4
• ATmega1284P
• ATmega2560 (see issue #2)

it should not be impossible to fit a normal serial bootloader (with automatic baudrate detection?) into the remaining bytes ... help is appreciated!

If you wish you can add CRC Check or versioning with EEPROM but I prefere to keep things simple. avr_boot will reflash your FIRMWARE.BIN as long as it is present. Is this a problem? No! It happens nearly instantly and only differing bytes are flashed really. You may consider putting your logic into your application and perform a CRC Check after the fact to inform the user and delete or rename FIRMWARE.BIN

• https://github.com/per1234 - Boards Manager Installation and help with differenct MCUs
• http://elm-chan.org/fsw/ff/00index_p.html
• Wilfried Klaas for the MCSDepthLogger https://github.com/willie68/OpenSeaMapLogger
• https://github.com/mharizanov/avr_boot
• https://github.com/osbock/avr_boot
• and others???

• https://spaces.atmel.com/gf/project/sdbootloader/
• https://github.com/thseiler/embedded/tree/master/avr/2boots
• http://www.mikrocontroller.net/articles/MMC/SD_Bootloader_f%C3%BCr_AT_Mega

... call me stupid, but I passed several days debugging those - without success ...