computer can’t recognize, and program the board. The VID/PID for the
bootloader is part of the bootloader file. To change this you will need to
recompile the bootloader with the new VID/PID, and upload it.
Why Does my ATMega32U4 Board Show up Twice in Device
Manager?
Both the bootloader and the sketch have their own VID/PIDs. When you
plug in a board the bootloader starts running for a few seconds, and you will
see the board show up in Device Manager based on those VID/PIDs. After
a few seconds, the sketch will start running, and you will see Device
Manager disconnect from the bootloader and connect to the sketch.
How Does the IDE Know Which COM Port to Use?
When the IDE resets the board, the COM port is disconnected from the
computer. The IDE then looks for a new COM port. This is the port it uses.
This is one of those weird things Arduino did to get things to work on this
chip.
How Do I Reinstall the Bootloader?
Check out or reinstalling the bootloader tutorial, which should work for both
ATMega32U4 and ATMega328 boards. If you have the tools to do so,
reinstalling the bootloader is often easier then trying to stay in the
bootloader. Since reinstalling the bootloader puts the board back in factory
settings this will reset the VID/PID numbers allowing your board to work
again.
Resources & Going Further
Thanks for checking out our Pro Micro and Fio v3 Hookup Guide! If you’re
looking for more resources related to these boards, here are some links:
• Pro Micro Schematic
• Pro Micro EAGLE Files
• Fio v3 Schematic
• Fio v3 EAGLE Files
• ATmega32U4 Datasheet
• ATmega32U4 Arduino Addon GitHub Repository
Going Further
Thanks for reading along with our Pro Micro hookup guide! Hopefully now
you’re fully prepared to begin using the Pro Micro in a project of your own.
Here are some tutorials that might be worth checking out as you continue
down the rabbit hole:
• Exploring XBees and XCTU
• Arduino Programming 101
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