Arduino Pro Micro: Reset & Restore Bootloader

If you’ve accidentally uploaded some code to the Arduino Pro Micro board as “Arduino Micro”, “Arduino Leonardo” or any other board, there is a big chance to brick your board by crashing its bootloader so it won’t be recognized by the PC at all anymore.

To revive the “bricked” Arduino Pro Micro you can try to reset the board and restore the bootloader by uploading any sketch with the board and processor options correctly set.

Cool Tip: Add “Arduino Pro Micro” board to the Arduino IDE! Read more →

Reset Arduino Pro Micro

The process of resetting of the Arduino Pro Micro is a bit tricky as it doesn’t have a hardware RESET button.

Nevertheless it still can be put in a bootloader reset mode by wiring twice the RST (reset) and GND (ground) pins – use for this a piece of a wire or create a temporary button.

Bootloader Reset Feature: Arduino IDE has only 8 seconds to access the board after you short twice the RST to GND to invoke the bootloader reset feature.

Follow these steps to reset the “bricked” Arduino Pro Micro board and reinstall the bootloader:

  1. Open an empty sketch in the Arduino IDE and select the correct board and processor:
    Top Menu -> Tools -> Board: "SparkFun Pro Micro"
    Top Menu -> Tools -> Processor: "ATmega32U4 (5V, 15MHz)"
  2. Connect the Arduino Pro Micro to the PC using the USB cable
  3. Quickly short the RST to GND twice and select the serial port that should appear in the Arduino IDE (you will have only 8 seconds for this):
  4. Top Menu -> Tools -> Port: "" -> Serial ports
  5. Start uploading the empty sketch (Ctrl + U) and when the status changes from “Compiling sketch…” to “Uploading…”, quickly short the RST to GND pins twice again and wait for uploading process to finish:
    Top Menu -> Sketch -> Upload

Once the status changes to “Done uploading.” it will mean that it worked – you have successfully reset the Arduino Pro Micro board and restored the bootloader.

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9 Replies to “Arduino Pro Micro: Reset & Restore Bootloader”

  1. couldnt reset my leonardo but tapping reset twice did the trick – cheers for saving my chip.

  2. Thanks for posting this. Other articles I’ve found that offer help with this issue have not mentioned that the “reset twice” action can be repeated during the process. Your technique completely solves my get-it-done-in-8-seconds stress…

  3. Thanks! I recently bought a 3V 8 MHz Pro Micro (clone) and bricked it at the first attempt to upload a schetch pretending the board was a Leonardo. I added the Sparkfun boards to the IDE as described above and flashed the boatloader using an Arduino Uno as ISP as described in This saved my Pro Micro!!
    Thank you very much for posting this!

  4. Sir, you are great! I read lot of stupid things on other sites, like “try to upload even no port appear in the system”. Following your instructions I was able to unbrick my Pro Micro.

    Thank you!

  5. In Arduino IDE (v1.6.8 & 2.0.3), there is no “Sparkfun Pro Micro” board, but there is a “Arduino Micro” board Which is supposedly compatible.
    The 8-seconds delay is indeed there when you double reset it. Loading a new program is never a problem when USB code is included in your programs; no need to ‘Reset’ before programming.
    Unfortunately, the 8-second delay is always there upon power-up.
    If someone knew how to modify the bootloader, such that the application runs without delay upon power-up, I would be very grateful.

    1. You can upload the sketch directly to the board… without any bootloader. Hence no 8-second bootloader, boot-up time anymore.

  6. I had to go back and re-install Arduino IDE VERSION 1 again to get it working. But after a few tries it did the trick. Thank you so much. Pro Micro working again!!!

  7. Thank you very much, you saved my Arduino.

  8. you saved my liiiifeeeee broooooooooo

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