20mhz arduino pro (un-supported, support)
by Moogle on Aug.24, 2010, under Arduino / AVR, Electronics
Sparkfun:
We actually had to retire this item because it is totally unsupported by the Arduino IDE.
http://www.sparkfun.com/commerce/product_info.php?products_id=8789
I can get it to work fully with just a few lines add to boards.txt
it is very simple.
open up boards.txt and add the following to the top
##############################################################
pro328_20.name=Arduino pro 328 20mhz
pro328_20.upload.protocol=stk500
pro328_20.upload.maximum_size=30720
pro328_20.upload.speed=57600pro328_20.bootloader.low_fuses=0xFF
pro328_20.bootloader.high_fuses=0xDA
pro328_20.bootloader.extended_fuses=0×05
pro328_20.bootloader.path=atmega
pro328_20.bootloader.file=ATmegaBOOT_168_atmega328_20.hex
pro328_20.bootloader.unlock_bits=0x3F
pro328_20.bootloader.lock_bits=0x0Fpro328_20.build.mcu=atmega328p
pro328_20.build.f_cpu=20000000L
pro328_20.build.core=arduino
magically this board also works at 3.3v :) and is now running my arduino web server at fugabarba.com
no problems that i can find. uart works and delayms works fine
if you are building your own 20mzh arduino be sure to patch the bootloader first
enjoy
March 11th, 2011 on 7:35 pm
Hi,
Are you sure your arduino is running at 20Mhz on 3.3v? The datasheet shows you will need power supply between 4.5v and 5.5v to achive 20Mhz speed. So I am a bit confused.
June 1st, 2012 on 9:42 am
The crystal will generally still run at 3.3v, but Atmel does not guarantee device stability at that threshold. Due to testing guard-bands most of the chips will probably work at that voltage.
I believe the chip is more susceptible to brown-outs at lower voltages. If you look at the data-sheet 16 MHz is a little too fast for 3.3v as well, but it has been running strong in many platforms for some time now.