Optiboot flash

Optiboot flash is an easy to install bootloader for the Arduino environment. This repository contains a total of 9944 precompiled hex files built for 53 different targets with 14 different clock frequencies and 9 different baud rates to choose from.

Key features:

• Small in size (<512 bytes when EEPROM upload support is disabled)
• Supports baudrates upto 1Mbit
• Supports write to flash within application
• Compatible with a most "classic" AVR microcontrollers
• EEPROM upload support
• Chips with 64kiB flash has flash page copy functionality, which is useful for a self-update application like ArduinoOTA

Supported devices

• ATmega640, ATmega1280, ATmega2560
• ATmega64, ATmega128, ATmega1281, ATmega2561
• AT90CAN32, AT90CAN64, AT90CAN128
• ATmega8535, ATmega16, ATmega32, ATmega164A/P, ATmega324A/P/PA/PB, ATmega644/P, ATmega1284/P
• ATmega8515, ATmega162
• ATmega8, ATmega88/P/PB, ATmega168/P/PB, ATmega328/P/PB
• ATmega165/P/PA, ATmega325/P/PA, ATmega645/P
• ATmega3250/P, ATmega6450/P
• ATmega169/P/PA, ATmega329/P/PA, ATmega649/P
• ATmega3290/P, ATmega6490/P
• AT90USB646/647, AT90USB1286/1287

Precompiled binaries

This repository contains a bunch of precompiled hex file with a variety of clock frequencies and baud rates:

	1000000	500000	460800	250000	230400	115200	57600	38400	19200	9600
24 MHz	X	X		X	X	X	X	X	X
22.1184 MHz			X		X	X	X	X	X
20 MHz		X		X		X			X
18.4320 MHz			X		X	X	X	X	X	X
16 MHz	X	X		X		X		X	X	X
14.7456 MHz			X		X	X	X	X	X	X
12 MHz		X		X		X	X		X	X
11.0592 MHz			X		X	X	X	X	X	X
8 MHz	X	X		X		X	X	X	X	X
7.3728 MHz			X		X	X	X	X	X	X
4 MHz		X		X					X	X
3.6864 MHz			X		X	X	X	X	X	X
2 MHz				X					X	X
1.8432 MHz					X	X	X	X	X	X
1 MHz										X

Using different UARTs

The table below shows the available serial ports for the corresponding microcontroller. This repository contains precompiled hex files if you want to use other serial ports than UART0.

Target	UART0	UART1	UART2	UART3
ATmega8/88/168/328 ATmega8515 ATmega8535/16/32 ATmega169/329/649 ATmega165/325/645 ATmega3250/6450 ATmega3290/6490	X
AT90USB646/647 AT90USB1286/1287		X
ATmega162 ATmega328PB ATmega164/324/644/1284 ATmega64/128 AT90CAN32/64/128 ATmega1281/2561	X	X
ATmega324PB	X	X	X
ATmega640/1280/2560	X	X	X	X

Bootloader LED pin

All precompiled binaries have an active LED output pin. The LED flashes twice when a hardware reset occurs. The table below shows which pin used used to drive the LED for a particular target:

Target	LED pin
ATmega8515, ATmega162	PB0
ATmega8535/16/32 ATmega164/324/644/1284	PB0, PB7
ATmega8/88/168/328 ATmega64/128/1281/2561 AT90CAN32/64/128 ATmega325/645 AT90USB646/647/1286/1287 ATmega165/325/645 ATmega169/329/649	PB5
ATmega640/1280/2560 ATmega3250/6450 ATmega3290/6490	PB7

Building from source

You need to have make installed. You also need avr-libc, avr-binutils and avr-gcc. Alternatively you can install Arduino IDE, which comes with all these packages except make. Install Arduino IDE 1.8.9 or newer to be able to build for the new ATmega324PB and ATmega328PB.

To execute the build script you can either cd into the optiboot_flash folder and run make, or you can execute the script directly by running ./makeall.
If you just want to build a single file for a single target you can instead execute a make command formatted like this:

make atmega8 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2 UART=0

Acknowledgements

Although it has evolved considerably, Optiboot builds on the original work of Jason P. Kyle (stk500boot.c),
Arduino group (bootloader), Spiff (1K bootloader), AVR-Libc group and Ladyada (Adaboot).

Optiboot is the work of Peter Knight (aka Cathedrow). Despite some misattributions, it is not sponsored or supported by any organisation or company including Tinker London, Tinker.it! and Arduino.
Maintenance of optiboot was taken over by Bill Westfield (aka WestfW) in 2011.
Flash write functionality added by majekw in 2015.