Sparkfun Pro Micro reset to bootloader

Using a Sparkfun Pro Micro as Button box interface for Racing Sim. (Keyboard interface)
Made changes to code and tried to download but now windows 10 saying device not recognized.
Tried to reset boot loader but cant beat the 8 second timer in Arduino IDE V1 or 2. Link on procedure below.
Have purchased a new board and will order another as spare once in stock but would like procedure to make further changes safely and also how to “unbrick” current board.

Is there a way to download bootfiles vie a serial to USB?

Thank you

Hi Graham,

Welcome to the forum :slight_smile: thanks for linking that guide you were trying to work through so we can get up to speed with the issue.

The procedure with the least dependence on external hardware and physical connections to be made will be to use the one outlined in the guide you linked and just reflash the code to the existing bootloader. Though as you’ve found out the timing can be a bit of an arbitrary dance when you need to have a few tries to see roughly how long it takes the code to compile so that you can give it a head start.
If you haven’t already added a physical reset button it will probably be a lot easier to nail the reset timing if you do.

If you do want to send the Pro Micro back to factory conditions and reinstall the bootloader you can but there are a few things to check:
Which specific version of the Pro Micro did you have? You’ll need to add a logic level converter if you are reflashing a 3.3V Pro Micro using an AVR programmer.
Do you have an AVR programming tool already?

Since the Pro Micro doesn’t include an ICSP header you’ll need to manually connect the AVR programmer pins to the pins shown below.

If you don’t have a dedicated AVR programmer handy you can use another Arduino device as a programmer, but I don’t recommend this route as it is very fiddly and there are a lot of configuration steps that have to be perfect or it simply won’t work.

This guide covers the bootloader reinstallation process and options in more detail.
My intuition would be to practice the timing and see if you can get lucky with reflashing the program that way, it might save you a lot of extra hardware and fiddling around, but if you’ve hit an impasse and need to reflash the bootloader, let us know how you are travelling and we’ll see if we can guide you through it.

Thanks Trent,

I currently have the 3.3V Pro Micro and have ordered a 5V version form Core.

I will be ordering another spare pro micro or recommended equivalent when you have them in stock.

Which AVR Programming tool do you suggest, I will add to my next order.

Also moving forward is there a link for the recommended process to make changes to the programming of a micro pro without bricking it!

I am trying to configure a toggle switch to send an on command when activated and deactivated (I have a toggle switch with rocket cover that I want to use as ignition. Sim is looking for momentary PB, I want to activate ignition by sending a pulse upon turning on toggle and sending another pulse upon deactivating toggle)

Youtube video with code below.

Hi Graham,

Earlier in that guide you linked it covers the process of which board settings to select in Arduino based on which Pro Micro version you have. The most important setting will be to identify which of your boards are 3.3V 8MHz boards and which are 5V 16MHz boards. Programming the board with the wrong settings is the most common way to brick these. How to change that setting is shown below.

Thanks Trent, I should have read a little closer. Got lost in the frustration.
Followed procedure again with correct board and fixed in minutes.

Back to the SIM!.

Note for others there was no indication I had the wrong board selected just kept failing to upload. I assumed incorrectly that I was missing the 8 second window.