A well known problem. Once you have disabled serial and JTAG programming, parallel programming is the only way to reset the fuses. See datasheet section 25.6 Parallel Programming.
Reviewing the documentation, I realized that disabling serial programming (SPIEN fuse) is not possible over serial programming, only over JTAG or parallel. Means you have not totally locked out further programming, but probably disabled the clock oscillator. In this case, it should work to connect an external clock source to pin XTAL1 to give programmer access.
I'm no expert in Atmega devices but the schematic suggests it generates the negative voltage needed for serial communication comes from a charge pump (D8/D9) so check if there is a signal leaving pin 4. If it isn't there, try an external clock source. If it still isn't there, looks like you need a JTAG programmer.
Brian.
Hi,
Yes, use no Xtal, but an oscillator.
Frequency: if I remember right, then it should with 1MHz and higher.
It will work with lower frequencies, but then you may need to slow down ISP clock frequency of the programmer, too.
Btw: this is what you can try anyway....
Klaus
I had similar problem programming ATmega16/32 on EasyAVR v7 and I guess I just removed the XTAL or plugged a low-frequency XTAL and programmed.
Hi,
Reset, brown out?
Wiring?
Supply?
I don't think it needs anything else..
Klaus
If it is locked when you used say 20 MHz crystal then put a 4 Mhz crystal on board and then in compiler settings change XTAL frequency to say 4 MHz and build it and try to burn. See if this works. I had done something like that when I had same issue of locking with mikroC PRO AVR Compiler, ATmega16/32/2560 and 16 MHz crystal and mikroProg for AVR programmer.
When it was locked it used the internal RC oscillator. I guess it was set to 8MHz I am not sure.
So what value of crystal oscillator should I try and is the exact value critical?
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