Hi Hasu,
Sorry for the late reply, but I've been trying out your suggestions, and I keep getting stuck.
Horsebadorties,
To be honest I don't know much about modern KVM technology and what 'dedicated' and generic port mean exactly.
But I know some users with KVM had trouble like that.
The dedicated USB ports on a KVM are for HID devices only. Some KVMs, including mine, use Dynamic Device Mapping (DDM) to emulate a connection between those ports and the computer (or computers) that are not actively connected. Many KVMs also monitor the dedicated keyboard port for a "hotkey" sequence that tells the KVM to switch active computers.
A generic USB port on the KVM can accept any device: another HID, or a printer, webcam, etc. With those ports, the KVM doesn't use DDM, or watch for hotkeys. The KVM deals with those ports the same way an ordinary USB switch does. I usually don't use these ports, because the computers "beep" when being switched.
What's your KVM model number actually?
Do the three keyboards work well on the 'dedicated' port?
Do you have any other keyboard which doesn't works well on the 'dedicated' port?
I have two KVMs:
Yes, all three of my current keyboards (GMMK TKL, Hexgears Impulse and Hexgears Nova) work well when connected directly to the KVM's dedicated port. I had another keyboard that would not work at all on that port: a Realforce R2 TKL. I discussed this with you in June (
https://geekhack.org/index.php?topic=72052.msg3062182#msg3062182), but then I returned the board.
It may be helpful to see difference between USB descriptors of the converter and those keyboards.
You can get USB descriptor of device using 'USB Descriptor Dumper'.
Flash the Dumpr firmware on your converter and just plug the device into the converter, you shoulld get USB descriptors on 'hid_listen'.
https://github.com/tmk/tmk_keyboard/wiki/USB:-Descriptor#usb-descriptor-dumper
https://github.com/tmk/tmk_keyboard/wiki#hid_listen
EDIT: And let me know what OS you are using.
As for firmware build options what is worth trying would be:
MOUSEKEY_ENABLE = no # Mouse keys
EXTRAKEY_ENABLE = no # Media control and System control
CONSOLE_ENABLE = no # Console for debug
I'm using Windows 10. I built TMP on a ubuntu VirtualBox (
https://github.com/tmk/tmk_keyboard/wiki/Build-on-VirtualBox), changed the options in the Makefile, ran 'make' and then 'make dfu'. When finished, this appeared on the console:
27104 bytes used (94.53%)
The modified firmware makes no difference. When the converter is between my keyboard and my KVM, I get missed and repeated keystrokes and delays, just like before. Unfortunately, I was unable to get the Dumper firmware and flash it on my converter. I just could not figure out how to do that. I'll try again later, when time permits.
Thanks for your help, Hasu!