so, you downloaded the new arduino beta software, you installed it, you ran the ide and blam, where are my old third party boards
you want to add back your third party boards but are not sure (or have tried) to add your third party mcu
so first off, download and install the appropriate arduino beta software
if you have an arduino due, you can read more about it on the official site
once you have your specific operating system flavor of arduino installed, navigate to the arduino folder inside hardware
[install location] -> right click arduino -> show package contents
regardless of which operating system you are on you will find two folders here, avr and sam
grab your third party hardware folder (typically containing boards.txt, bootloader folder, cores folder, programmers.txt) and create a new folder for it here
in this example, we have created a new folder named '644' which contains the sanguino core from 'picasso' github
now that we have a new folder setup with our hardware (in this case, the '644' folder), you will want to copy the platform.txt file from the 'avr' folder and paste it in your new one
open the newly pasted platform.txt file in your favorite text editor
name=(line 5 in the recent release)
name=value, we changed ours to urm, other chips so
name=urm, other chipsis what we typed
in the image above you now see a sub menu in 'boards' with a section title of 'urm, other chips'
with platforms out of the way, in your new folder (again 644 in our case), find and open boards.txt
menu.cpu=Processor to the top of the file, this will invoke the 'processor' sub folder under 'tools'
save, relaunch arduino and booom, you now have a new 'boards' sub menu with
well, you can do what you did in the platforms and boards section over and over, but what if you simply have a processor variant
here, we are going to add an 328 non-pico to the mix, but we don't want it in a new subfolder, we simply want to add a processor to the mix
atmega328diecimilasection and scroll down to
menu.cpu.atmega328diecimila.[identifier]for the following
menu.cpu.atmega328diecimila.[identifier].bootloader.file=optiboot/optiboot_atmega328.hexyes, we shoehorned the optiboot onto the 328 non pico
menu.cpu.atmega328diecimila.[identifier].build.mcu=m328auit's what we called it in the avrdude.conf file
sub menu in 'boards' with the identifier 'three two eight'
sub menu in 'processor' with the identifier 'non picante (bootloader)'