Extended Fuses Settings, 0x05=0xFF ?

Using Arduino Microcontrollers
1

Hello,

Basically, I don't know how to interpret the fuses settings. I have an Arduino Uno R3 SMD edition, and at the fuses calculator site (AVR® Fuse Calculator – The Engbedded Blog) it says that the default extended fuses are 0xFF, which if I understand correctly, means that the BOD is disabled. Now when I go to the boards.txt file, it says that the extended fuses settings are set to 0x05. Is that the same thing and if yes, why?

Thanks in advance, and apologies if the topic is in the wrong section.

2

No, they're not the same thing.
0x05 sets BOD level at 2.7V
0xFF, as you say, disables BOD.

You might find this calculator more informative:- AVR Fuse Calculator for ATmega328P

3

Thanks.
Any ideas why my extended fuses were not at the default settings? I have never touched them before. It would also be helpful if you could give me some steps on how to change them to 0FF.

4

Fuses can be chaged during the bootloading e.g. (Tools -> Burn Bootloader), or non lama user can do it via avrdude tool from command line. However, you have to have an ISP programmer or second Arduino (Arduino as ISP).

5

PizzaGuy:
Thanks.
Any ideas why my extended fuses were not at the default settings? I have never touched them before. It would also be helpful if you could give me some steps on how to change them to 0FF.

The default settings you talk about are not the "Arduino" defaults, as I understand it they're the standard blank chip defaults.
You could effectively call the "Boards.txt" settings the "Arduino" default settings for the board.

If you want to do it the relatively easy way, and gain a few other extra features, you could install MCUdude's "MiniCore". It allows you to select a BOD level in the IDE to suit your preference, and sets the fuses accordingly.
It also allows you to choose from a range of clock options, both internal and external.
It supports the ATMega328 as well as the ATMega328P, too, and the ATMega8, ATMega48, ATMega88 and ATMega168.
As an added bonus, it adds support for writing to and reading from flash program memory at runtime. (I tested this a few weeks ago and it works well.)

Installing the core is easy, you just add this line to ">File >Preferences >Additional Boards Manager URLs" :-
https://mcudude.github.io/MiniCore/package_MCUdude_MiniCore_index.json

Here's a link to the GitHub page if you want to check it out:- MiniCore

N.B. You still need to do the "Burn Bootloader" step to set the fuses, with an ISP programmer or Arduino as ISP programmer.
If you don't already have one, it's well worth buying a USBASP programmer, (about $2), to make this step nice and easy now and in the future. Better than messing around setting up an Arduino to do it.

6

f you don't already have one, it's well worth buying a USBASP programmer, (about $2), to make this step nice and easy now and in the future. Better than messing around setting up an Arduino to do it.

Yes, I agree with OldSteve, the USBasp is great tool for ridiculous price.

7

Thanks for your help. I will definitely try MiniCore soon.