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20mhz arduino pro (un-supported, support)

by 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=57600

pro328_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=0x0F

pro328_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


2 Comments for this entry

  • avatar
    Visitor

    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.

    • avatar
      Mr. Joe

      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.

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