Arduino Uno, lower clock to 8MHz [internal]

hi there,

i've been digging through forums not able find solution.

final result: low power atmega328 sensor node powered 2xaa batteries.

current goal: take out original atmega328 chip arduino uno v3 board [externally clocked @ 16mhz] , switch atmega328 clocked internally @ 8mhz , have working slowed down original.

so far i've managed build circuit , flash original arduino uno bootloader fresh chip. switching newly flashed chip original 1 worked great [ able flash program , run it, @ 16mhz of course].

unfortunately attempts @ switching atmega 8mhz yield no results. 1.6.5 ide gives endless timeouts while 1.0.1 gives avrdude: stk500_getsync(): not in sync: resp=0x00 error.

i have tried following setups, x = 57600, 38400, 9600
1. copy of original settings of arduino uno, fuses changed use internal 8mhz oscillator , lower dropout voltage
unolp.name=arduino/genuino uno [ 8mhz / low power ]
unolp.upload.tool=avrdude
unolp.upload.protocol=arduino
unolp.upload.maximum_size=32256
unolp.upload.maximum_data_size=2048
unolp.upload.speed=x

unolp.bootloader.tool=avrdude
unolp.bootloader.low_fuses=0xe2
unolp.bootloader.high_fuses=0xde
unolp.bootloader.extended_fuses=0x06
unolp.bootloader.unlock_bits=0x3f
unolp.bootloader.lock_bits=0x0f
unolp.bootloader.file=optiboot/optiboot_atmega328.hex

unolp.build.mcu=atmega328p
unolp.build.f_cpu=8000000l
unolp.build.board=avr_uno
unolp.build.core=arduino
unolp.build.variant=standard

---

2.
guide: https://maniacbug.wordpress.com/2011/10/19/sensor-node/
bootloader file: https://github.com/codebendercc/arduino-core-files/blob/master/v100/hardware/arduino/bootloaders/atmega/atmegaboot_168_atmega328_pro_8mhz.hex

lopower.name=arduino ultru low-power (<2.4v, 8 mhz) w/ atmega328

lopower.upload.protocol=stk500
lopower.upload.maximum_size=30720
lopower.upload.speed=x
lopower.upload.tool=avrdude

lopower.bootloader.low_fuses=0xe2
lopower.bootloader.high_fuses=0xda
lopower.bootloader.extended_fuses=0x06
lopower.bootloader.path=atmega
lopower.bootloader.file=atmegaboot_168_atmega328_pro_8mhz.hex
lopower.bootloader.unlock_bits=0x3f
lopower.bootloader.lock_bits=0x0f
lopower.bootloader.tool=avrdude

lopower.build.mcu=atmega328p
lopower.build.f_cpu=8000000l
lopower.build.core=arduino
lopower.build.variant=arduino:standard

--

what else can have chip running @ 8mhz on uno board ? appreciated.

thanks.

hi,

can straighten few things out? trying run atmega @8mhz on uno board, or on else, e.g. breadboard?

if on uno board, trying power 2aa batteries, or usb power?

if on breadboard, using usb-serial adaptor? uno socket empty?

paul

Arduino Forum > Using Arduino > Microcontrollers > Arduino Uno, lower clock to 8MHz [internal]

arduino