We found that an ATmega32U4 (like the Pro Micro 3.3V/8MHz) can brown out when outputting power to a boost
converter. While code can run after uploading, a power cycle from the initial current draw to a boost converter is
enough to cause the Pro Micro brown out. Thus causing the sketch to not run. This requires the user to toggle the
reset button after a power cycle.
Frequently Asked Questions
If you're having technical difficulties with your Qwiic Pro Micro, see if any of the answers to these FAQs help. If not,
please get in touch with our tech support team.
VID is short for 'Vender Identification' and PID is short for 'Part Identification'. In other words, this pair of IDs
defines the device. This is how your computer knows what you've plugged in, what drivers to use with it, what
COM port is assigned to it, etc. All native USB devices have a VID/PID.
All SparkFun ATmega32U4 boards share the same VID -- 0x1B4F, and they all have unique PIDs. 5V Pro Micros
lay claim to PIDs 0x9205 and 0x9206 (one for the bootloader, one for the sketch). 3.3V Pro Micros will show up as
0x9203 and 0x9204 for bootloader and sketch, respectively. And the Fio v3 has 0xF100 and 0xF101.
How Can I Change the VID and PID on an ATMega32U4 Board?
Every time you upload code the VID and PID are uploaded to the device. These values are located in the
'
boards.txt
' file and will therefore be determined by the board you have selected. Keep in mind that if you select
the wrong board you will get the wrong VID/PID uploaded which means the 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 and Going Further
Thanks for checking out our Qwiic Pro Micro Hookup Guide! If you're looking for more resources related to these
boards, here are some links:
