Howto recover wrong fuses settings on a AVR

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();
}
}

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admin April 15th, 2007


40 Responses to “Howto recover wrong fuses settings on a AVR”

  1. # madeon 26 Jul 2007 at 5:05 am

    How about my problem?
    i have the same problem but i use atmega8535, assembly.
    thank’s.

  2. # Jkxon 09 Jan 2008 at 7:40 pm

    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

  3. # kalandaon 01 Feb 2008 at 12:44 am

    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;
}

  4. # nmcon 22 May 2008 at 4:24 am

    Thanks a lot for the tip. It really helped!

  5. # Santiagoon 09 Jul 2008 at 2:55 am

    i’d like to know if I need only set the external clock and the default values back, or I need make anything else

  6. # adminon 09 Jul 2008 at 9:14 am

    Santiago, you need to set the right fuse (clock, reset flag etc ..)

  7. # Danielon 23 Aug 2008 at 3:26 am

    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.

  8. # Danielon 23 Aug 2008 at 3:27 am

    I meant 32khz not 32hz..

  9. # adminon 23 Aug 2008 at 1:11 pm

    I don’t know .. You should give it a try.

  10. # Natureon 31 Aug 2008 at 7:32 pm

    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?

  11. # pragon 07 Oct 2008 at 7:13 am

    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.

  12. # adminon 07 Oct 2008 at 10:05 pm

    prag, re-read this howto perhaps :)

  13. # Gabrison 20 Nov 2008 at 1:35 am

    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

  14. # saraon 02 Mar 2009 at 12:45 pm

    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

  15. # jXP3on 12 Mar 2009 at 2:47 pm

    For me it worked perfectly just using CKOUT of another microcontroller(attiny2313).

  16. # jejenon 13 Apr 2009 at 10:51 am

    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

  17. # ckeayson 30 May 2009 at 2:55 am

    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

  18. # Dolphinon 14 Jul 2009 at 11:31 am

    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?

  19. # arimarjulon 21 Jul 2009 at 1:48 pm

    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!!!

  20. # adminon 21 Jul 2009 at 11:06 pm

    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..

  21. # Dolphinon 22 Jul 2009 at 11:32 am

    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.

  22. # VidProon 21 Oct 2009 at 9:12 pm

    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.

  23. # VidProon 21 Oct 2009 at 9:15 pm

    The #include should be &lt avr/io.h &gt

  24. # Ben Ryveson 26 Oct 2009 at 1:21 am

    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.

  25. # farezon 09 May 2010 at 1:25 pm

    can i use oscillator 1mhz ?

  26. # Sandeep Kumaron 20 Aug 2010 at 7:03 am

    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.

  27. # sanjayon 11 Sep 2010 at 9:37 am

    Thanks ,thanks , thanks a lot.
    I required 2Atmega16 and 2 atmega 32 with this method.
    Perfectly worked for me .

  28. # sanjayon 11 Sep 2010 at 9:38 am

    sorry for mistake in above comment, i recovered 4 microcontroller using this method .

  29. # shrison 05 Jan 2011 at 3:12 pm

    How to recover locked ATMEGA644???

  30. # Harleyon 06 Feb 2011 at 12:43 am

    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.

  31. # josephon 03 Mar 2011 at 4:44 am

    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

  32. # brownon 06 Apr 2011 at 5:59 pm

    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 !!

  33. # Kpaxon 06 Jun 2011 at 2:54 pm

    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.

  34. # Malon 10 Jun 2011 at 5:22 pm

    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 ?

  35. # bmx64on 26 Jun 2011 at 11:41 am

    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….

  36. # Andriansahon 16 Aug 2011 at 6:52 pm

    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

  37. # karthik con 08 Oct 2011 at 9:35 pm

    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.

  38. # kin3zuon 02 Nov 2011 at 5:38 pm

    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

  39. # styledivaon 22 Jan 2012 at 4:55 pm

    i have placed 8Mhz external crystal.how can i do the settings of fuse bits for that???..help..

  40. # styledivaon 23 Jan 2012 at 12:13 pm

    we are using 8MHz crystal… How to set the fuse bits for that..

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