I could really use some help from someone who knows USB, HID, keyboards, the intricacies of PCs interacting with keyboards at POST and such.
I have a Raspberry Pi Zero emulating a USB keyboard. It works great. However if I connect it via my KVM, two of my older PCs will not complete POST. Unplugging the Pi from the KVM's keyboard port solves this. Connecting the Pi directly to the PC solves this. No real keyboard has this issue.
Code and more details: https://gist.github.com/QBFreak/b7bc6a7421c2df8da63a43324c25e372
I found a post where someone had a similar issue, and using their Report Descriptor I was able to get the device to show up without any errors when connected directly to the PC. It still fails to function through the KVM. I'm beginning to think it's a lost cause. Once again, I updated the comments at the end of the gist.
@QBFreak Many KVMs, at least the more enterprise models have the ability to present the KB as "present" and BIOS on most modern machines has the ability to boot without keyboard. You could set that and see if you get a boot. There may also be polling frequency for the KB in the KVM's setup, if it's not a simple unit.
@gedvondur I'm trying to cobble an enterprise level KVM experience out of a budget KVM and stuff I found on Amazon. I'll look through the manual again but I don't think I could customize anything to that detail. It's just a "cheap" IO gear that's a number of years old. I'll poke around the BIOS a little more, but they aren't failing with a missing keyboard error (I remember those days), they're just hanging. One in the middle of drawing a character on the screen.
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