Support for Urboot and Mighty/Mini/Mega/MajorCore v3.0.0

[MCUdude]

Version 3.0.0 of Mighty/Mini/Mega/MajorCore has been released, and Optiboot has been replaced with Urboot.
Urboot is superior to Optiboot in virtually every way (Read more about the excellent Urboot bootloader here), but it will require different fuse settings. Optiboot is still bundled, but Urboot should be the default bootloader.

Status	Task	Can be done without further ado	Who?
✅	Update Avrdude to 7.2-arduino.1 (7.2 is backwards compatible with 7.1, so all cores that uses 7.1 can be upgraded to use 7.2)	YES	@valeros or @ivankravets
✅	Update Mighty/Mini/Mega/MajorCore to v3.0.0	YES	@valeros or @ivankravets
🟡	Update fuses and bootloader script to support Urboot, and make Urboot the default bootloader for all Mighty/Mini/Mega/MajorCore targets	NO, a PR for this are needed first. See PR #321	@MCUdude

When everything is done, I'm thinking about providing a template like this to help users get the most out of these cores (the current version of the template can be found here):

[platformio]
default_envs = Upload_UART ; Default build target

; Common settings for all environments
[env]
platform = atmelavr
framework = arduino

; TARGET SETTINGS
board = ATmega1284P
board_build.f_cpu = 16000000L
board_build.variant = standard

; BUILD OPTIONS
build_unflags =
build_flags = 

; SERIAL MONITOR OPTIONS
monitor_port = ${env:Upload_UART.upload_port}
monitor_speed = 9600

; Run the following command to upload with this environment
; pio run -e Upload_UART -t upload
[env:Upload_UART]
upload_protocol = urclock
upload_port = /dev/cu.usbserial*
; Urboot has auto-baud detection, so "any" baud rate can be used
board_upload.speed = 250000


; Run the following command to upload with this environment
; pio run -e Upload_ISP -t upload
[env:Upload_ISP]
upload_protocol = custom
upload_flags =
  -C$PROJECT_PACKAGES_DIR/tool-avrdude/avrdude.conf
  -p$BOARD_MCU
  -cusbasp
upload_command = avrdude $UPLOAD_FLAGS -U flash:w:$SOURCE:i


; Run the following command to set fuses
; pio run -e fuses_bootloader -t fuses
; Run the following command to set fuses + burn bootloader
; pio run -e fuses_bootloader -t bootloader
[env:fuses_bootloader]
board_hardware.oscillator = external ; Oscillator type
board_hardware.uart = uart0          ; Set UART to use for serial upload (For Optiboot, use "uart0_optiboot")
board_hardware.bod = 2.7v            ; Set brown-out detection
board_hardware.eesave = yes          ; Preserve EEPROM when uploading using programmer
upload_protocol = usbasp             ; Use the USBasp as programmer
upload_flags =                       ; Select USB as upload port and divide the SPI clock by 8
  -PUSB
  -B8

Bottom line:

• upload_protocol = urclock are backwards compatible with upload_protocol = arduino
• Millions(!) of pre-compiled Urboot bootloader binaries can be found here, including the ones bundled with Mighty/Mini/Mega/MajorCore
• Optiboot will still be available, but board_hardware.uart = uartN_optiboot has to be specified to burn Optiboot. upload_protocol = arduino is also required for uploading using the Optiboot bootloader

[valeros]

Hi @MCUdude, the packages have been uploaded:

• https://registry.platformio.org/tools/platformio/tool-avrdude/versions
• https://registry.platformio.org/tools/platformio/framework-arduino-avr-minicore/versions
• https://registry.platformio.org/tools/platformio/framework-arduino-avr-megacore/versions
• https://registry.platformio.org/tools/platformio/framework-arduino-avr-mightycore/versions
• https://registry.platformio.org/tools/platformio/framework-arduino-avr-majorcore/versions

[MCUdude]

Thanks @valeros!
I'll try to find some time next week to implement Urboot support for the fuses.py and bootloader.py scripts.