When a Pro Micro is externally reset (by pulling the RST pin low), it'll only briefly (<750ms) start the bootloader before continuing on to the sketch.

For some embedded projects, waiting eight seconds before a program runs isn't acceptable, so we modified the bootloader run time. When a Leonardo (or any device using the 'stock' bootloader) is externally reset, it goes back into the bootloader.and waits there eight seconds before it starts running the sketch. We ship the Pro Micro with a modified version of the Arduino Leonardo bootloader, with one major enhancement.

Open Arduino back up, check the Serial Ports menu again.

Wait a few seconds for the device to be detached.

If you can't see your Pro Micro's serial port, give these steps a try: There are a few series of events that can lead to its serial port being removed from the Arduino IDE's Serial Port selection menu. The Pro Micro can be a finicky little thing. Serial Port Not Showing Up in 'Tools > Board' Menu

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How Can I Change the VID and PID on an ATmega32U4?.

Code Runs Upon Upload But Fails to Start After Power Cycle.Serial Port Not Showing Up in 'Tools > Board' menu.

Here's a directory of the subjects covered: On this page you'll find troubleshooting tips and FAQs. Share on Twitter Share on Facebook Pin It Troubleshooting and FAQ

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