Optiboot on 8MHz Arduinos

Hi all,

Is anyone using the optiboot bootloader on arduinos running at 8 MHz? I'm myself trying to make it work on a custom board (3.3V, 8MHz) without success. For the standard bootloader, I usually take the one built for the "atmega328_pro8" platform , just changing LFUSE to 0xE2 (internal 8MHC RC oscillator) and it works great. However, doing the same for optiboot does not work. I get no pin flashing, just a quick blink on the RX/TX LED's. I'd even say that the uC is not being reseted but I'm not sure.

Thanks guys for your feedback.

I run optiboot on 8MHz Atmega168 chips without any issues.

Are you running optiboot on a custom board? Are you using DTR for reseting the atmega? Which optiboot image have you flashed into your Atmega168? I've myself tried "atmega328_pro8"


Yes, I use an FTDI based adapter (moderndevice ‘BUB’) with DTR on a custom board. The bootloader file is this: ‘optiboot_pro_8MHz.hex’.

If it helps, the fuse settings are (ATmega168, 8MHz internal oscillator, 512 bytes (256 words) bootloader): lfuse: 0xE2, hfuse: 0xDD, efuse: 0x04


I'll give optiboot_pro_8MHz.hex a try on my Atmega328P-based board.

Before you go through all the process: is your baud rate correctly set to 115200?

madworm: Before you go through all the process: is your baud rate correctly set to 115200?

Not sure, I just select "Optiboot Atmega328P pro 3.3V 8 MHz" or something similar from the boards menu. I guessed that doing this would set the proper serial speed.

Hmmm. Then that's not a standard board ;-) The only optiboot entry the vanilla V22 comes with is the uno. The rest is still 57600 at best.

I had no optiboot entry until I created a hardware folder in my Sketches dir, containing the downloaded optiboot dir, as explained in the wiki:

Do you mean that none of the new optiboot entries set the correct baud rate?

Thanks again!

No, I wouldn't dare say that. The arduino V22 I downloaded from this site already has optiboot in it. One notable difference between optiboot and the previous bootloaders is a drastically shorter timeout. If the delay between reset and a communication attempt is too long it doesn't work.

Thanks a lot for your help madworm.

I’ve finally tried both optiboot_atmega328_pro_8MHz.hex and optiboot_pro_8MHz.hex from Arduino 022 choosing different boards (“Arduino Uno” and “[Optiboot] Arduino Pro or Pro Mini (3.3V, 8MHz) w/ Atmega328”). None of the combinations worked on my Atmega328P 3.3V @8MHz(internal osc) board.

Anyway, this is not a big problem since I can still stay with the old bootloader :slight_smile:

Hi, why I don't have any [optiboot]bootloader listed in the Board menu? Thanks