[SOLVED] Set Low Fuse Bit, Now Can't Program over ISP

Using Arduino Microcontrollers
59

dc42:
It's making more sense to me now:

  • with 128kHz applied to XTAL2 you are getting 16KHz on CLKOUT
  • so you need to program it with SCLK not exceeding 4KHz
  • so -B 250 is barely enough cycle time, if avrdude does use the -B parameter to set the SCLK rate of the AVRISPmkII

So try with 128KHz applied to XTAL2 again, but this time:

  • try avrdude with a -B parameter greater than 250
  • try using AVR Studio, with the SCLK frequency in the user interface set to 4KHz or even lower.

If that fails, try with 32768Hz or so applied to XTAL1 or XTAL2 (whatever gives you a clean CLKOUT signal) and use SCLK <= 1kHz in AVR Studio. The docs say you can't program the flash below 2KHz, but you can do a chip erase.

Yep! That worked. I set the clock source (D9) from the Arduino to 128KHz and connected it to XTAL2. After that, I went into AVR Studio and set the rate to 4.209KHz (or something very close) and the connection was very unstable. Though, I was able to set the fuses back to factory state after trying to write them a few times. Now it's working without the external clock source!

I'll try to write the low fuse to use the resonator tomorrow, or sometime soon, but correctly this time :slight_smile:

Thanks a lot dc42, and all!