How to modify Arduino boards.txt to support new MCUs In this post, it was mentioned that to get the Arduino IDE to support an ATmega328 (only the ATmega328P is supported):


  I should mention the Arduino way of doing this, is to create a new
  boards.txt file with this chip and add (not change) the avrdude.conf
  file. This will allow programing either from selecting the correct
  board. but that is another subject.


After a great deal of research in the past, and attempted modifications to boards.txt and avrdude.conf, I arrived at the conclusion that the Toolchain doesn't support the ATmega328 therefore the changes will have no effect.

Can anyone confirm that they have successfully found a way to make these changes, so we can avoid the need for a work-around?
Please, Note that the Arduino IDE is behind on many of the tools. In this case avrdude and its conf file, along with avr-gcc 

First:

.\arduino-1.5.6-r2\hardware\tools\avr\etc\avrdude.conf


needs to support the m328 in addition to m328p. This can be done by either updating 

.\arduino-1.5.6-r2\hardware\tools\avr\bin\avrdude.exe


to something like avrdude-6.1-svn-20131205-mingw32. along with replacing the conf file with the new one

.\arduino-1.5.6-r2\hardware\tools\avr\etc\avrdude.conf 


file that has both m328 along with the m328p. Note 6.1 supports a parent method, making it easy to duplicate chips with different signatures. Or use existing 5.11 and add to its 

.\arduino-1.5.6-r2\hardware\tools\avr\etc\avrdude.conf 


file by duplicating the entire m328p section and renaming the new entry to "m328" along with the correct signature.

Second:

avr-gcc need to be updated to support compiling both the m328p and m328. Yes, it just a semantic thing. But the next part will send either ATmega328p or ATmega328 to both gcc and dude. which both need to support it. One can simply copy over 

.\arduino-1.5.6-r2\hardware\tools\avr\ 


with the new tool chain. I used avr-gcc-4.8_2013-03-06_mingw32

Third:

replace the following line in boards.txt

uno.build.mcu=atmega328p


with

## Arduino ATmega328P
## ---------------------------------------------
uno.menu.cpu.atmega328p=ATmega328P
uno.menu.cpu.atmega328p.build.mcu=atmega328p

## Arduino ATmega328
## ---------------------------------------------
uno.menu.cpu.atmega328=ATmega328
uno.menu.cpu.atmega328.build.mcu=atmega328


This will add an option to the IDE when UNO is selected for either chip. And subsequently send the correct MCU to both the compiler and avrdude.



Proof: 

Below are the verbose output of the IDE with the above changes. Note the -mmcu and -p for both options. As a real unit is was not connected it yielded the "not in sync" error. Where this shows it all works.

C:\projects\Arduino\arduino-1.5.6-r2\hardware\tools\avr\bin\avr-g++ -c -g -Os -w -fno-exceptions -ffunction-sections -fdata-sections -MMD -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=156 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR -IC:\projects\Arduino\arduino-1.5.6-r2\hardware\arduino\avr\cores\arduino -IC:\projects\Arduino\arduino-1.5.6-r2\hardware\arduino\avr\variants\standard C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp\sketch_jul31a.cpp -o C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp\sketch_jul31a.cpp.o 
...
C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp/sketch_jul31a.cpp.hex 

Sketch uses 444 bytes (1%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
C:\projects\Arduino\arduino-1.5.6-r2/hardware/tools/avr/bin/avrdude -CC:\projects\Arduino\arduino-1.5.6-r2/hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328p -carduino -PCOM3 -b115200 -D -Uflash:w:C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp/sketch_jul31a.cpp.hex:i 

avrdude: Version 5.11, compiled on Sep  2 2011 at 19:38:36
...
avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude done.  Thank you.




C:\projects\Arduino\arduino-1.5.6-r2\hardware\tools\avr\bin\avr-g++ -c -g -Os -w -fno-exceptions -ffunction-sections -fdata-sections -MMD -mmcu=atmega328 -DF_CPU=16000000L -DARDUINO=156 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR -IC:\projects\Arduino\arduino-1.5.6-r2\hardware\arduino\avr\cores\arduino -IC:\projects\Arduino\arduino-1.5.6-r2\hardware\arduino\avr\variants\standard C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp\sketch_jul31a.cpp -o C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp\sketch_jul31a.cpp.o 
...
C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp/sketch_jul31a.cpp.hex 

Sketch uses 444 bytes (1%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
C:\projects\Arduino\arduino-1.5.6-r2/hardware/tools/avr/bin/avrdude -CC:\projects\Arduino\arduino-1.5.6-r2/hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328 -carduino -PCOM3 -b115200 -D -Uflash:w:C:\Users\mflaga\AppData\Local\Temp\build6597836883576934105.tmp/sketch_jul31a.cpp.hex:i 

avrdude: Version 5.11, compiled on Sep  2 2011 at 19:38:36
...
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude done.  Thank you.