On Sun, 2018-03-25 at 22:05 +0300, Kimson Muriungi wrote: > Hi guys, > > I have a custom mega 2560 avr control board that I just got bricked > by setting the wrong fuses accidentally. It is surface mount, so i > cannot use fuse bit doctor or high voltage programming to reset it. > Sadly I also didnt include JTAG in my design. The fuses have been set > to Low frequency crystal oscillator. The only thing I have around > that could help is a USBTiny ISP programmer, and a 32khz crystal, > which i hoped would probably provide the low frequency to make it run > as per the fuse settings. I have not managed to change that until > now. I am aware that ISP programming frequency should be utmost 1/4 > of the 32 khz. Is there a way I can set ISP frequency of that level > (6 to 8 khz) using avrdude and command prompt? Probably I'll be able > to reset the fuses this way. > > Or if there is any other way Id bring this chip back, I'd gladly use > it. > Avrdude has the -B switch you can set it to 125 to get an 8KHz ISP clock that would work with a cpu clack of 32KHz. You'll then to inject the 32KHz clock into the XTAL1 pin of the 2560.
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