atmega328p - fuse settings to ensure brown out detection at 2.7v

Using Arduino Microcontrollers
1

So, I've bootloaded my atmega328p with a suitable 3.3v 8MHz bootloader (ATmegaBOOT_168_atmega328_pro_8MHz.hex). It works fine. But I am about to run the chip from a 3.7v lipo (hence this new bootloader) and I want to make sure it has BOD at 2.7v. I have googled around this, but can't at the moment find the answer to this question: what should the fuse settings be to have BOD at 2.7v? Or how do I work the answer out? (I have looked at AVR® Fuse Calculator – The Engbedded Blog but I cannot make head/tail of it).

The current settings (from the boards.txt file) are:
diecimila328.bootloader.low_fuses=0xff
diecimila328.bootloader.high_fuses=0xdd
diecimila328.bootloader.extended_fuses=0x00

Thanks in advance,

Ben

2

You're using fuse settings for a 168 processor. Try starting with settings for a 328P processor.

3

I cut and paste the wrong section from boards.txt. The current settings are:
pro328.bootloader.low_fuses=0xFF
pro328.bootloader.high_fuses=0xDA
pro328.bootloader.extended_fuses=0x05

Does that help with an answer?

Ben

4

I'd add "Preserve EEPROM memory through the Chip Erase cycle; [EESAVE=0]"...

pro328.bootloader.low_fuses=0xFF
pro328.bootloader.high_fuses=0xD2
pro328.bootloader.extended_fuses=0x05

BOD at 2.7 V was and is enabled.

5

thanks, coding badly. very helpful. ben