tsessebe / microbridge-arduino-atmega2560

Modified BootLoader to load firmware from sd or flash

USB and SDCARD Firmware flashing for the ARDUINO ATMEGA 2560 and ADK

⚠️Note: This fork has been modified to work with the Arduino Mega2560 rev3 with an Arduino Ethernet Shield (which includes an SD card reader). Keep in mind, on the Mega, the hardware SS pin, 53, is not used to select either the W5100 or the SD card, but it must be kept as an output or the SPI interface won't work. Also, this fork changes the EEPROM flag address from 0x1FF to 0xFFF, the last EEPROM address on the Mega2560.

master branch is sdcard flash bootloader_from_flash is flash from an spi chip

mechanics :

The bootloader looks for byte in eeprom at address 0xFFF:

-if it is set to 0xF0 bootloader will look for a bin file on the sdcard named 
 firmware.bin and use it to flash the firmware then reset the byte to 0xFF so it
 does this only once

-otherwise no action is taken and bootloader works as a arduino bootloader except
 some of the debugging functions are missing

Setup ADAFruit micro sdcard 5V ready:

SDCARD on ATMEGA 2560 or ADK

pin 50  -  DO

pin 51  -  DI

pin 52  -  CLK

pin 53  -  CS

if you have an sd card shield which is different from this setup you need to change 
the pinout in asmfunc.S and recompile the bootloader !!!

Flashing bootloader :

- copy the entire 'hardware' folder to your mydocuments/arduino folder 

- restart arduino ide

- you should now see under tools -> boards  -> Arduino mega 2560 (Dual sd bootloader) (select this)

- set the appropriate programmer

- burn bootloader

Using arduino ISP bootloader :

- connect arduino atmega 2560

- upload sketch 'Arduino ISP' (found in file -> examples)

Atmega2560 to Atmega 2560 connections:
	programmer	-	receiver
	pin 50			pin 50
	pin 51			pin 51
	pin 52			pin 52
	pin 53			reset
	5v				5v
	ground			ground
aditionally on programmer you have to put a capacitor between reset and ground (2.2microf works)
if you don't do this it won't work !!!

Compile bootloader:

install Crosspack (http://www.obdev.at/products/crosspack/index.html)

Navigate to My Documents/arduino/hardware/microbridge/bootladers/microbridge/

issue :

- make clean

- make all

bootloader output :

Size after:
AVR Memory Usage
----------------
Device: atmega2560

Program:    6116 bytes (2.3% Full)
(.text + .data + .bootloader)

Data:        333 bytes (4.1% Full)
(.data + .bss + .noinit)

Generate BIN file:

To generate a bin file you need issue the following command on you apps elf executable :

avr-objcopy -I elf32-avr -O binary firmware.cpp.elf firmware.bin

this generates firmware.bin which can be put on the sd for flashing your firmware. You can find the elf file in you apps build directory.

Using olimex usb to upload bootloader: avrdude -c stk500v2 -p m2560 -P /dev/tty.usbmodemfd131 -B 500 -e -u -U lock:w:0x3F:m -U efuse:w:0xFD:m -U hfuse:w:0xD8:m -U efuse:w:0xFF:m -F

avrdude -p m2560 -c stk500v2 -P /dev/tty.usbmodemfa131 -F -U flash:w:stk500boot.hex -b 115200 -B1 -U lock:w:0x0F:m

avrdude -p m168 -c usbtiny -e -u -U lock:w:0x3f:m -U efuse:w:0x00:m -U hfuse:w:0xDD:m -U lfuse:w:0xFF:m


avrdude -p m2560 -c stk500v2 -P /dev/tty.usbmodemfd131 -U flash:w:stk500boot_v2_mega2560.hex -U lock:w:0x0F:m -v 
avrdude -c stk500v2 -p m2560 -P /dev/tty.usbmodemfd131 -U lock:w:0x3F:m -U efuse:w:0xFD:m -U hfuse:w:0xD8:m -U lfuse:w:0xFF:m -e -v