It looks like I broke my Arduino (Compatible) Pro Mini board using AtmelStudio to change the fuses. I was having trouble with speed and using some basic sketches. For example, the LED blink was on for 2 seconds and off for 2 seconds instead of 1 second. I tried to change the fuses to Ext Clock + 65 ms, and now I can't use the thing at all. Cannot enter programming mode. Any ideas?

  • Sound like you selected a Pro Mini 16MHz in the IDE, but are actually using a Pro Mini that is running at 8MHz.
    – Gerben
    Apr 10, 2016 at 16:14

1 Answer 1


Sounds like you broke your fuses.

You may be able to enter programming mode by applying an external clock signal to the clock in pin (use another Arduino to generate it). If that doesn't work then the only way to fix it is with a "High Voltage Programmer".

Nick Gammon has a very good tutorial here: http://www.gammon.com.au/forum/?id=12898

  • Also if you managed to get a clock divider activated, you may need to slow down the clock rate of the programmer to something sufficiently slower than the effective internal clock rate. May 9, 2016 at 22:25

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