Fuses settings brownout and programming

Other Hardware 3rd Party Boards
1

HI All,

I need some help with a fuse problem. I have a custom circuit board in an art project. The systems uses atmega328p with a 16M crystal. The chips are bootloaded as Duemilanove. At this speed data sheet says voltage must be >4.5V. If the voltage drops below 4 I have experienced brownout program corruption issues.

I want to change the fuse for brownout detect to set it to 4.3V

The standard fuse setting for these chips in the arduino board file is

low: 0xFF
high 0xDA
ext: 0x05

the extended fuse in this case sets brownout to 2.7V.
based on : AVR® Fuse Calculator – The Engbedded Blog

My desired setting is (based on link above) :
low: 0xFF
high 0xDA
ext: 0x04

when I set the fuses like this brownout works perfectly -- exactly what I want.

HOWEVER: I now have to reset power to upload code. (explicitly, first upload no reset needed. Subsequent uploads need power reset).

I have tried also (larger bootload size)
low: 0xFF
high 0xD8
ext: 0x05

good brown out -- reset power to upload code.

Is it possible to have 4.3V brownout and no need for reset press to upload-- or is this some impossible pipe dream of mine? (Why does it work once? -- consistently).

I am not familiar enough with the bootloader / reset line interactions to know if this possible.

Please, if anyone can advise, what fuse combination will allow 4.3 brownout AND no need for reset press to program.

s

2

Are you saying you want to set the RSTDISBL (External Reset Disable) fuse in addition to the BODLEVEL fuses and are wondering what the correct fuse bits are?

3

HI RalfD ( and everyone else ) :

After a ton of testing I realized my error was not the fuses but I sketchy connection on DTR line of a new programming board.

Fuse setting indicated above appear fine for my context after a few days of tests.

Ralfd -- thanks for taking the time to reply.

s