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Help me rescue my ATmega32a?

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avrfan

New Member
I used a website to calculate the fuse settings for my ATmega32a but I missed one of the settings and have accidentally written fuses to expect an external clock instead of using it's internal oscillator as I had intended. (The fuses written are E: FF, H: D9, L: F0)
I can no longer write new programs to it, nor rewrite the fuses.
Besided the ATmega32a, I have avrdude, a USBtiny, and an arduino.
I've tried programming a simple blink loop into the arduino to set a pin high for 1ms and low for 1ms, and connected that to XTAL1 on the ATmega32a as an external clock source while trying to rewrite the fuses but I couldn't get that to work. I'm not sure if I should have expected it to work.
Is it possible to simulate an external clock with an arduino sufficiently well for a USBtiny to let me write my intended fuse settings? Do I need to supply any special arguments to avrdude?

Here is what I see with the arduino connected to XTAL1
Code:
 $ avrdude -c usbtiny -p atmega32 -vv

avrdude: Version 6.2
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/etc/avrdude.conf"
         User configuration file is "/home/ac/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : usb
         Using Programmer              : usbtiny
avrdude: usbdev_open(): Found USBtinyISP, bus:device: 003:011
         AVR Part                      : ATmega32
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PA0
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom         4    10    64    0 no       1024    4      0  9000  9000 0xff 0xff
           flash         33     6    64    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           lock           0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00
           calibration    0     0     0    0 no          4    0      0     0     0 0x00 0x00

         Programmer Type : USBtiny
         Description     : USBtiny simple USB programmer, http://www.ladyada.net/make/usbtinyisp/
avrdude: programmer operation not supported

avrdude: Using SCK period of 10 usec
CMD: [ac 53 00 00] [ac 50 00 00]
CMD: [ac 53 00 00] [ff f3 00 00]
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.


avrdude done.  Thank you.
 
Last edited:

avrfan

New Member
I was trying to do that, in a way, using the arduino to supply the external clock pulses.
If that's not a viable solution could you suggest which physical clock components I would need?
And is there a guide anywhere I could follow?
 

spec

Well-Known Member
Most Helpful Member
I was trying to do that, in a way, using the arduino to supply the external clock pulses.
If that's not a viable solution could you suggest which physical clock components I would need?
And is there a guide anywhere I could follow?
Our posts crossed. In the meantime I had updated my post #4 which may answer some of your questions.

But if you need a list of specific components, can you let us know what clock frequency you would like to use. The clock frequency is a trade off between processing speed, power supply voltage, and current consumption.

So if you can let us know what your power supply voltage is (the supply line must be decoupled by a 100nF (or over) ceramic capacitor connected close to the supply + and 0V pins on the AVR chip) and what your priorities are, one of us can post a definitive components list (three low-cost components).

spec

UPDATE 2016_12_17: I can't figure exactly what fuses you have blown- can you post a list using the fuse names and values described in the ATmega32A data sheet.
 
Last edited:

avrfan

New Member
I'd like to use the internal oscillator at 1MHz and I've been using a 5v supply.

The fuses I've set were calculated using this page: http://www.engbedded.com/fusecalc
This describes the clock setting that I've written to be :
"Ext. Clock; Start-up time 6CK + 0ms; [CKSEL=0000 SUT=00]"
whereas I should have chosen :
"Int. RC Osc. 1MHz; Start-up time: 6CK + 64ms; [CKSEL=0001 SUT=10]"

Otherwise, the other settings are
BODEN=0
BODLEVEL=1
BOOTRST=0
BOOTSZ=00
EESAVE=0
CKOPT=0
SPIEN=0
JTAGEN=0
OCDEN=0

It's a useful website - if you type in the fuse settings near the bottom of the page, it updates to tell you what they mean.


Thanks for updating your reply, and thanks for the circuit diagram you've added. Are you showing how to add a crystal to XTAL1 and XTAL2? I thought that an external clock source and a crystal were different things.
I tried connecting a 16MHz crystal (which is all I have) between XTAL1 and XTAL2 with capacitors as you've described but running the same command as above (avrdude -c usbtiny -p atmega32 -vv) is not successful.
 

spec

Well-Known Member
Most Helpful Member
Are you showing how to add a crystal to XTAL1 and XTAL2? I thought that an external clock source and a crystal were different things.
I tried connecting a 16MHz crystal (which is all I have) between XTAL1 and XTAL2 with capacitors as you've described but running the same command as above (avrdude -c usbtiny -p atmega32 -vv) is not successful.
Hi avrfan,

thanks for information. Yes, you are quite correct there are a number of non internal clock sources:
(1) Xtal
(2) Ceramic resonator
(3) RC
(4) External clock

I had not read the ATmega32A data sheet fully or understood fully what you said in your OP.

But generating an external clock (4) only requires the connection of one small package. If this approach is of any interest, just say and specify the frequency you require and what supply voltage you are using for your ATmega32A.

spec
 

avrfan

New Member
Hi,

To try to make things easy (?), let's say 5volt, 16MHz. I have a 16MHz crystal.

The longer version is that I am interested in any approach that can allow me to rewrite the fuses with the limited kit that I've got, which rules out high voltage programming, but I do have a 16MHz crystal resonator, and I'm happy to use it and have the MC run at 16MHz.
As I mentioned, I have a 5 volt supply, but I also have a 3.3volt supply that I could use too. My preference is 5V.
Ideally I'd write the fuses to use the internal 1MHz oscillator but if I need to have the chip run at 16MHz as an intermediate step, then I'm happy to do it.
I think that rules in options (3) and (4), and I thought both of those involved connecting to XTAL1 (and XTAL2), so I'm not sure whether option (1) is an entirely separate option that I'm unaware of, but I'm potentially interested in that. I don't think I have a ceramic resonator and don't have a high voltage supply or high voltage programmer, so those are both out.
 

spec

Well-Known Member
Most Helpful Member
Hi avarfan,

Perhaps I did not make it clear what I am suggesting which is to use an external clock permanently and leave the fuses as they are.:)

None of the clock options (1) to (4) will allow the fuses to be reprogrammed.

spec
 
Last edited:

avrfan

New Member
I see, I had not understood that. Thanks for clarifying.
So it seems that for now my microcontroller is beyond rescuing, in which case I will resort to using a different microcontroller.
Perhaps I will investigate a high voltage solution one day in the future to try to reset the fuses, but for now that is not an option available to me.
Thanks for all your help
 

spec

Well-Known Member
Most Helpful Member
I see, I had not understood that. Thanks for clarifying.
So it seems that for now my microcontroller is beyond rescuing, in which case I will resort to using a different microcontroller.
Perhaps I will investigate a high voltage solution one day in the future to try to reset the fuses, but for now that is not an option available to me.
Thanks for all your help
No problem avrfan- sorry for the misunderstanding. I should have made my initial post clearer.:)

Good luck with your AVR projects.

spec
 
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