Messed up reset pin, can't reprogram

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Hey, a while ago, I think I configured the reset pin on my Tiny25 to be an I/O pin. Now I can't program the micro any more. How do I fix it? Do I need a crystal or an oscillator? I didn't set any fuses low or anything.

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Just throw it away and buy another chip.

A Tiny85 will have more memory and run the same code.

David.

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You need a high voltage programmer to reset this fuse bit, e.g. the STK500.

If you want to use all 6 IOs together with further programming, you must program a bootloader into the AVR at first.

Peter

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Recently I had "save" two attiny13 throught HVSP, and I have more to "save"...
Dragon has HVSP..

Regards,

Bruno Muswieck

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ok, thanks guys. all i have is an AVRISP mkII, so I guess this micro is done for. good thing I bought extras.

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When you have a handy collection of dead AVRs, you pop them round to Melbourne.

I understand that everyone in Australia is within walking distance of Melbourne.

Someone may restore them for you.

David.

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Haha, I'm not actually in Australia. I just like wombats lol.

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There are several programs on the web and projects here for reviving AVR chips that have had their RESET pins fused into I/O pins.

They all involve both creating a switchable regulated +12v source (from a 78L12 and a transistor) that gets applied to the reset pin of Lazarus AVR, and sending a precise sequence of ISP re-enabling pulses to specific pins. A second AVR is used to create these pulse sequences. The code for the control AVR often needs to be adapted to the specific 'dead' AVR.

I've built one from plans on the web, but it didn't work. I've used a Dragon to re-program the fuses using the HV algorythm and this did work. Unfortunately, the AVR Dragon self-destructs much more easier than the AVR chips themselves.

All this would have been a lot easier if the AVR had been designed to restore itself to ISP-accepting mode when a specific frequency of 50% duty-cycle, VCC/Gnd pulses (say 2.45KHz to 2.55KHz) could be applied to the reset pin for several seconds. This would be immune to random reset pulses and switch-debounce sequences, and could be implemented with a simple 555-timer.

Don't discard the Tiny25 just because it's currently locked in non-ISP mode. Someday you're likely to get a Dragon and the IC can be easily restored.