COM Port Changing During Install Preocess

Hey there folks.

I have a Proxmark 3 Easy that had firmware previously installed on it 5-5 years ago.

I was planning to update the Proxmark while using a new computer running Windows 11 Home.

I followed the Getting started with the proxmark3 easy guide, but when I get down to the Flash your pm3 section and try to use the ./pm3-flash-bootrom command, my Ports in Windows Device Manager change from Port3 to Port4 and the install process fails:

pm3 ~/proxmark3$ ./pm3-flash-bootrom
[=] Session log C:\ProxSpace\pm3/.proxmark3/logs/log_20230715.txt
[+] About to use the following file:
[+] C:\ProxSpace\pm3\proxmark3\client../bootrom/obj/bootrom.elf
[+] Loading ELF file C:\ProxSpace\pm3\proxmark3\client../bootrom/obj/bootrom.elf
[+] ELF file version Iceman/master/v4.16717-103-g5f8cd5cac 2023-07-14 20:10:40 cdf68ab2f

[+] Waiting for Proxmark3 to appear on COM3
[|] 59 found
[+] Entering bootloader…
[+] (Press and release the button only to abort)
[+] Waiting for Proxmark3 to appear on COM3
[/] 0
[!] ERROR: invalid serial port COM3

[?] Try the shell script ./pm3 --list to get a list of possible serial ports
[!!] Error: Proxmark3 not found.
[!] The flashing procedure failed, follow the suggested steps!
[!] Sending bytes to Proxmark3 failed.offline
[+] All done

[=] Have a nice day!

pm3 ~/proxmark3$

The Proxmark3 Easy stays stuck with a green and red LED.

Does anyone know whats going on? Did I brick my Proxmark? How would I know if it is bricked?

Any info would be much appreciated!


Yep this happens sometimes. It’s easy to deal with.

Basically, when your proxmark is appearing on a different COM port than what you expect, you go into device manager and expand the ports listing, find the com port that the proxmark is on now, right click that, go to properties, go to advanced settings, in there somewhere you will be able to change the com port. Change the port to the expected port. Hit okay to confirm and you’ll have to basically unplug and replug the proxmark again and run through the process but this time it should stay on the correct com port.

What’s happening is that the bootloader and the application appear as different USB IDs to Windows and Windows is assigning a different COM port to the bootloader than the application… What you’re doing when you change the com port is you’re telling Windows hey I want this USB ID to be on com4 or whatever, and then also I want this other USB ID to also be com4… Windows will warn you that there are already devices assigned to the com port but just tell it to bugger off and accept. That way your bootloader and your application will both appear to Windows as the same comm port and you should have no more problems running through the update process.


Great explanation, boss! :+1:


Strange, today it’s not bugging up! :slight_smile:

It will still fart and hesitate for a few seconds when I use the ./pm3-flash-bootrom and ./pm3-flash-fullimage but it eventually proceeds. Phew!

Thanks for your help and suggestions!


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