Arduino Mega 3.3V 8Mhz

Using Arduino Microcontrollers
1

Hi,

I would like to know if anyone have a bootloader to make an Arduino Mega in 3.3V@8Mhz?
Or if someone can explain to me how change the bootloader ?

Thanks a lot for your help!

Sani300

2

You should be able to use the existing bootloader at 8MHz by using an upload baud rate of 57600 instead of 115200:

##############################################################
mega8m2560.name=Arduino Mega 2560 at 8MHz

mega8m2560.upload.protocol=wiring
mega8m2560.upload.maximum_size=258048
mega8m2560.upload.speed=57600

mega8m2560.bootloader.low_fuses=0xFF
mega8m2560.bootloader.high_fuses=0xD8
mega8m2560.bootloader.extended_fuses=0xFD
mega8m2560.bootloader.path=stk500v2
mega8m2560.bootloader.file=stk500boot_v2_mega2560.hex
mega8m2560.bootloader.unlock_bits=0x3F
mega8m2560.bootloader.lock_bits=0x0F

mega8m2560.build.mcu=atmega2560
mega8m2560.build.f_cpu=8000000L
mega8m2560.build.core=arduino
mega8m2560.build.variant=mega
##############################################################
3

According to the datasheet : ATmega2560/ATmega2561: 0 - 16MHz @ 4.5V - 5.5V
It doesn't matter how slow it runs, it needs at least 4.5V.

4

So, if I put the Arduino bootloader that we find in the Arduino IDE, and if i supply my micrcontroleur in 3.3V@8Mhz. I will be able to programming my board with the arduino software ?

That is what you said?

5

No. The ATMega2560 chip used on Mega boards is not spec'ed to run at 3.3V. It needs 4.5V.

The ATmega328P chip will run at 3.3V/8 MHz.
Select Promini 3.3V/8MHz for a board type when you bootload it.

6

Okay thanks a lot for your help!