SparkFun Forums

[sm4rty]

hello,

tried to flash h and l fuses

but i made a mistake

avrdude -p m8 -c sp12 -U lfuse:w:0xc9f:m -U hfuse:w:0xc9:m and now i cant flash it with my sp12 programmer anymore.

what can i do?
i flashed 2 chips and both dont recognize anymore

please help

[leon_heller]

Use an external oscillator; something like a 555 will do, it isn't critical. You can then reset the fuses.

[sm4rty]

hmm where can i get an oscillator?

is it possible to get it from old hardware?
or build it myself?

sorry i am a newbie in avr things.
tried it with a 14mhz crystal and an 100µF capacitor but didnt work

can you please describe what i have to do on which pins of the atmega8-16pu?

thank you verry much

[leon_heller]

As I said, you can make one from a 555 chip. Or, find a suitable oscillator module or buy one if necessary. You'll find more details on the AVR Freaks forum.

[sm4rty]

tried it with an 17Mhz crystal got it to be recognized 2 times but hadnt flashed it. today i wanted to flash the atmega8 but it will not be recognized.

is it possible that i have killed my atmega with the one Mhz more frequency? or that i killed my parallel port with a short circuit?

[leon_heller]

If the fuses have been set for an external oscillator a crystal won't work. You need an actual oscillator to reset them.

[sm4rty]

sorry i had blackout^^i meant a oscillator dont know why i wrote crystal.

its an 17Mhz oscillator which i connected to my atmega8 to the xtal1 (pin 9) and to pin 7 vcc and 8 GND.

i assume that its the right pinout and i used a 100µF capacitor so that it should run the atmega at 17Mhz but dont know if i made a mistake and produced a short cut or something.

i meassured the voltage and could it be a problem that the chip gets only 3.6V from the parallel port?
and thats the reason why it wont run with 17Mhz?

sorry for my bad english im from germany.

and its really difficult to ask something which you dont know ( i cant find the right words^^)

[leon_heller]

17 MHz is too fast. You need something like 1 MHz.

Where is the 100 uF capacitor connected?

[sm4rty]

i connected it like this picture:



but i dont have something with 1mhz.
hmm have to cut a few old hardware parts apart maybe i can find something

[n1ist]

If you have another AVR available, you can program it with a program that just toggles an output pin, and use that as a clock source.
/mike