Howto recover wrong fuses settings on a AVR

Posted on April 15, 2007 by admin

Yesterday, I ran into a issue with an ATMega32. In fact, I wanted to disable the Jtag support on the chips because I need to use the pins used by the Jtag (PC2-PC5). To disable the Jtag, you simply need to change some fuses. I changed the fuses with the help of the Avr Fuse Calculator, but I messed my ATMega with the wrong clock source. I don’t know how, but I choose the low freq clock. So my ATMega was totally frozen, as the clock settings was wrong, I was unable to reflash it, and worst, unable to change the fuses.

After a little googling, I found there is 3 ways to fixe this kind of issue:

Use a Jtag (as it doesn’t need a clocked micro)
Use a high voltage programmer (you can erase the fuse, with a programmer that do a parallel programming with RESET plug to a 12v PSU). This kind of programmer aren’t really easy to find. The only one I know right now is the STK500
Use an external clock (This is what I used, and describe here)

As, I don’t have any Jtag, or STK500, the only way to fix that is to use an external clock. In fact, I decided to ask on the #avr channel on freenode. And a really kool guy (“rue_mohr”) give me this tips. On every AVR micro, you can use a external clock if you messed the fuses settings. Simply plug a external clock on the clock pin (XTAL1 on the Mega32), and changes the fuses by this way.

Of course, you need a external clock at something like 1Mhz. Of course I don’t have this kind generator at home, but this can be easily done with another AVR micro this something like this:

void main()
{
  DDRA = 0xFF;
  while (1)
  {
     PORTA = ~PINA;
     nop();  // added some nop, to slow the clock a bit
     nop();
   }
}

46 thoughts on “Howto recover wrong fuses settings on a AVR”

made on July 26, 2007 at 5:05 am said:

How about my problem?
i have the same problem but i use atmega8535, assembly.
thank’s.
Jkx on January 9, 2008 at 7:40 pm said:

Moses just me this link on his weblog, but due to baysien filters, the url have been filtered. This post fix that issue.

Evil Mad Scientist

Thanks Mose

This really works, Thanks. I tried with an attiny13 and this code to simulate 1Mhz clock. Only i needs to set the ISP Freq. on the programmer to lowest rate (51.1hz) that is more slower but works.

// Library includes
#include 
#include 
int main()
{

  DDRB = 0xFF;
  while (1)
  {

   PORTB = ~PINB;
   asm volatile("nop");
   asm volatile("nop");
  // _delay_ms(1000); // Uncomment this line to probe if something is live :)
  }
return 0;
}

nmc on May 22, 2008 at 4:24 am said:

Thanks a lot for the tip. It really helped!
Santiago on July 9, 2008 at 2:55 am said:

i’d like to know if I need only set the external clock and the default values back, or I need make anything else
admin on July 9, 2008 at 9:14 am said:

Santiago, you need to set the right fuse (clock, reset flag etc ..)
Daniel on August 23, 2008 at 3:26 am said:

I was wondering.. can I use a similar method if I can only get a 32hz instead of 1mhz input? I have 3 atmega168 AVR that are unusable due to some fuse setting.. We switched tabs between fuse writes & now we can’t program/erase the chips any more.
Daniel on August 23, 2008 at 3:27 am said:

I meant 32khz not 32hz..
admin on August 23, 2008 at 1:11 pm said:

I don’t know .. You should give it a try.
Nature on August 31, 2008 at 7:32 pm said:

What do you mean?

You only have to feed EXTCLK on X1 & that’s it or you has to do so when you gonna program it?
prag on October 7, 2008 at 7:13 am said:

i am using atmega 1281 with stk500/501.

Kindly clear me, how to configure fuse bits.
i am not able to download my program onto the chip, as i have changed some fuse settings..

Thanks.
admin on October 7, 2008 at 10:05 pm said:

prag, re-read this howto perhaps :)
Gabris on November 20, 2008 at 1:35 am said:

It’s possible to have this code (down) in assebly?????

// Library includes
#include
#include
int main()
{

DDRB = 0xFF;
while (1)
{

PORTB = ~PINB;
asm volatile(“nop”);
asm volatile(“nop”);
// _delay_ms(1000); // Uncomment this line to probe if something is live :)
}
return 0;
}

thanks
sara on March 2, 2009 at 12:45 pm said:

hi thanks for your greatfull website; i want to khnow how can i access to the program of locked ic(atmega8l) &my programmer is universal2000. thanks
jXP3 on March 12, 2009 at 2:47 pm said:

For me it worked perfectly just using CKOUT of another microcontroller(attiny2313).
jejen on April 13, 2009 at 10:51 am said:

I do not have any other microcontroller, what if using the LPT printer port? please give this code to generate clock using LPT parallel port … thanks
ckeays on May 30, 2009 at 2:55 am said:

I found a website that sells a programmer to fix any avr. It only cost $29 and I fixed all of my locked atmega’s!

http://www.microcontrollerprog.com
Dolphin on July 14, 2009 at 11:31 am said:

I had used this way to recover wrong fuses settings on my AVR (ATmega8, ATtiny13) and it had worked perfectly. After then, I set wrong fuses again, I used this way to recover but it didn’t worked. I don’t know why, could you help me?
arimarjul on July 21, 2009 at 1:48 pm said:

HI!
I have a worst problem. I work with a atmega 8/16/32 and use a AVRISPmkII to program them.
But the problem occurs when some uC has the SPIEN fuse in ’1′.(serial programming disabled).
What can I do to fix this problem? I have a great amount of this uC.
Please help me!!!
admin on July 21, 2009 at 11:06 pm said:

Dolphin : Perhaps you need to explain, what you screw up ..

Arimarjul : You have to use a parallel programming mode .. this can be done with a STK500, or a JTAG if you don’t break the Jtag enable fuse ..

The parallel flash is the ultimate one, but this require to have a special programmer like the STK500..
Dolphin on July 22, 2009 at 11:32 am said:

I mean that I can’t use this way to recover my AVR which has been recovered before (more clearly, I can use this way only one time). This is my programmer : http://www.lancos.com/prog.html . So, this is my problem.
Thanks.
VidPro on October 21, 2009 at 9:12 pm said:

I had bricked 2 Atmega8′s and used the external clock method with this code running on another atmega8:

#define F_CPU 1000000UL /* 1 MHz CPU clock */

#include

int
main (void)
{
DDRC = _BV (PC0); /* PC0 is digital output */

while (1) /* loop forever */
{
/* set PC0 on PORTC (digital high) */
PORTC &= ~_BV(PC0);

}

return (0);
}

I then connected pin 23 if the working avr to pin 9 of the bricked avr and then restored the fuses. Worked for me on the 2 I screwed up… maybe it will help others

used AVR studio to compile.
VidPro on October 21, 2009 at 9:15 pm said:

The #include should be &lt avr/io.h &gt
Ben Ryves on October 26, 2009 at 1:21 am said:

Thank you for posting this! Rather than program another microcontroller, you can use a standard crystal oscillator circuit, such as one of these – http://z80.info/uexosc.htm – to coax the AVR back to life.
farez on May 9, 2010 at 1:25 pm said:

can i use oscillator 1mhz ?
Sandeep Kumar on August 20, 2010 at 7:03 am said:

Hi,
I was using UniPro10 programmer from ucmicrosystems for programming of ATmega32. But this programmer went bad. I tried to program the same ATmega32 chip with PonyProg (Through Serial Port of PC). It is giving error “Device missing (-24)”. Also I am not able to erase it. But the same programmer i.e. Pony Prog is working well with fresh Atmega32. Can I recover my old Atmega32? Plz help.
sanjay on September 11, 2010 at 9:37 am said:

Thanks ,thanks , thanks a lot.
I required 2Atmega16 and 2 atmega 32 with this method.
Perfectly worked for me .
sanjay on September 11, 2010 at 9:38 am said:

sorry for mistake in above comment, i recovered 4 microcontroller using this method .
shris on January 5, 2011 at 3:12 pm said:

How to recover locked ATMEGA644???
Harley on February 6, 2011 at 12:43 am said:

Thanks heaps! I found it was to also easy to use a spare 8mhz clock crystal lying around. Just manually touch the 2 pins of the crsytal to your xtal pins and then set the fuses. I wiped the fuses on four 44TQFP AVRS on assembled boards with a dodgy elf file, and with a little squinting could fix them just by holding the clock crystal pins against the soldered joints just long enough to change the clock back to internal RC.
joseph on March 3, 2011 at 4:44 am said:

i have programmed the above program in atmega32 from where i can take the clock output to give into another atmega as a external clock
brown on April 6, 2011 at 5:59 pm said:

i am using extreme burner to burn the program(written using codevision compiler) into an atmel mega 32 chip. i dont have a clue as to how to set the low and high fuse bits in the extreme burner. how to understand which clock frequency must be set?? i am new to this. please help !!
Kpax on June 6, 2011 at 2:54 pm said:

Thanks a Ton guys, this just works perfect, awesome find, i just recovered my bricked Atmega32 soldered on a board by touching the XTAL 1 pin to another uC generating a 4 MHz clock and re writing the Fuse using using the SPI programmer. Great work.
Mal on June 10, 2011 at 5:22 pm said:

This did not work for me on a ATtiny2313 with either 1Mhz or 4Mhz.
I accidentally inverted the low/high fuses (wrote L:DF, H:64), thus disabling the external reset.

Anyone with a similar scenario have any success ?
bmx64 on June 26, 2011 at 11:41 am said:

hi kpax, I am a newbie to uC, I have bricked a quadcontroller board with atmega48pa .can you help by submitting a detailed schematic diagm of how you actually do this, and what frequency is required for atmega48pa….
Andriansah on August 16, 2011 at 6:52 pm said:

Thank you very much, my three chips can now be used again,

This code in Bascom:

$regfile = “m8def.dat”
$crystal = 16000000

Ddrc.5 = 1

Do
Portc.5 = Not Portc.5
nop
nop
Loop

End
karthik c on October 8, 2011 at 9:35 pm said:

Pardon for my ignorance,One of my atmega32 is not working when i tried to set fuse bits
in extreme burner AVR software.I tried to set fuse bits such that it uses an external crystal clock source. i.e. set high byte 89 and low byte FF.
but after programming when i tried to read contents the software shows error like this
“Powering on failed
cannot able to communicate with target chip…”
and i does not changed SPIEN value,
please tell how to recover the chip.
thanks in advance.
kin3zu on November 2, 2011 at 5:38 pm said:

hello. i have used this method for ATmega16 and ATtiny2313 and it works. i have AVRPROG usb2 programmer (is polish i think) thank you. best regard
stylediva on January 22, 2012 at 4:55 pm said:

i have placed 8Mhz external crystal.how can i do the settings of fuse bits for that???..help..
stylediva on January 23, 2012 at 12:13 pm said:

we are using 8MHz crystal… How to set the fuse bits for that..
Javier on February 1, 2012 at 8:54 am said:

Hi
I’am programming the atmega32 and I have a problem with the FUSES. I intented to program the MCU with a crystal of 8Mhz. I program the FUSES: Hfuse>0xC9 and Lfuse>FF. Nothing happened. Afther I program the Fuses: Hfuse>0xD9 and Lfuse>FF. Nothing happened.
The MCU programmer is AVRISP.
I don’t understand. Would you mind explaining that further?

The system where I have programming is LCD and USART.
The fuses got from the datasheet atmega32.

Thanks.
vinod on April 13, 2012 at 4:19 pm said:

Hi,i am using atmega 32 microcontroller for serial transmission and reception with the pc using rs 232 interface.How to use the external clock {16mhz} to synchronize the data wat i sent .I was getting some mistakes whenever i used external clock using khazama programmer tat microcontroller cannot be programmed further as it got disabled whenever i used external clock in setting in khazama programmer.So what might me the issue???.Help me out.
admin on April 16, 2012 at 12:44 am said:

@stylediva @Javier @vinod : This is off-topic.
Qasim Rizvi on March 23, 2013 at 8:43 pm said:

I generate 12Mhz by using other Atmega8 and successfully recover my Atmega8
zmemw16 on December 20, 2013 at 10:39 pm said:

i just use an attiny85 on internal oscillator with clkout enabled.
generally useful as well.
DarwinS on February 9, 2014 at 9:53 am said:

Hi There,

i also have a problem on my atmega32. im trying to fix my bad fuse. can you make the circuit diagram the way you fix your avr?

Regards
Darwin

Jkx@home

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Howto recover wrong fuses settings on a AVR

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