AVR fuse bits

[Paranshu Singhal]

I have by mistake written low fuse bit 0xE5 instead of 0xE4. High fuse bit: 0x99. Now the microcontroller has become unresponsive and shows rc=-1 in BurnOMat every time i try to programme it or chage the fuse bit.My board consists of an external qyartz oscillator but nor RC. Ca anybody please tell me how to rectify this siuation???

[Ashutosh Bhatt]

one thing is to connect external RC in place of crystal

becuse after setting fuse bits you have to make your external circuit as per fuse bits settings

 

another way is to get new micro controller chip

 

[AJISH ALFRED]

Ya, I think thats the only option. Connect the external RC circit and chage the fuse bit once it works fine. You should be very careful when changing the fuse bits!!

[Shishir K Chakravarthy]

One more solution that worked for me…If u have another arduino or atmegaXX microcontroller, configure one of the pins to toggle at 1MHz and connect it to XTAL1 (Note that power must be connected to the faulty microcontroller). Wait for a few seconds. If it still doesnt work, try connecting it to XTAL2 (Because i dont remember which pin i connected it to)

 

This is the code for the recovery atmega:

 

void main(){

 

    DDRB|=1<<0;

    PORTB|=1<<0;

    while(1){

    PORTB^=1<<0;

    _delay_us(1);

  

   }

 

}

 

 

Cheers!

[Ashutosh Bhatt]

i have gone through same problem. I changed the fuse bits settings to connect external crystal. 

when i inserted programmed micro controller into new board it does not work. then I figured out i had to connect external crystal now to make it work. 

so when i connect external crystal to XTAL input pins it starts working.

[Shishir K Chakravarthy]

After inserting the external oscillator, and making it work, u can reprogram the device with default fuse bits to make it work without the eternal oscillator too…

[Ashutosh Bhatt]

yes that is always possible

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