avrdude: ser_open(): can't open device "\\.\COM5" Sparkfun Pro Micro

Using Arduino Avrdude, stk500, Bootloader issues
#1

Hi,

I have some issue with the upload of sketch on a sparkfun pro micro board with the processor ATMega32U4 (3.3V, 8MHz).

It seems that my board is/was bricked. Actually, i'm able to upload a sketch but it needs ugly bootloader mode. The working sequence I am using now is :

State = COM6 on device manager & COM6 selected on Tool>Port

Double hit reset button : Bootloader mode activation
State = COM5 on device manager & COM6 selected on Tool>Port

Upload Sketch
Double hit reset button : Keep bootloader mode activation
Wait for Found Upload port COM5

Keep double hitting on reset button while the sketch is uploading (sometimes I double hit 3 or 4 times before the sketch is uploaded)

If i have the good timing (if I don't double hit when the sketch uploads) the upload works. Otherwise I have a "can't open device COM5" because of the double hits.

By the way, sometimes when I reactivate bootloader mode, the board doesn't start correctly and is no longer known by my PC which cause the failure of my sequence.

#2

Maybe it helps to enable verbose output during upload in preferences.

For a Leonardo it shows the process and you can see when it tries to establish the connection (switching from COM6); that would be the moment to press the reset button. I don't have a pro Micro but it should be very similar.; in your case double tap, I guess.

#3