I'd imagine it would be very difficult, and would require a relatively powerful MCU. Ben Eater's made a few videos discussing how PS/2[0] and USB keyboards[1] work. USB's a vastly more complicated protocol compared to PS/2.
You only need a bare minimum host controller (USB 1.1) to accept a keyboard, and hardcode everything in the firmware to assume one. A suitable MCU is pretty cheap:
As for relative lack of availability, I think that says more about how many people want to use an old keyboard with a new computer (semi-common) vs. a new keyboard with an old computer (rare).
The CH554 is a microcontroller with an E8051 core with a 24 MHz clock, a little more than 1 kB of RAM, and a bit more than 14 kB split between the code and data Flash.
I think that qualifies as "relatively powerful" when compared to a Z80 or 6502. :-)
I do agree that the lack of such adapters is due to zero market demand though.
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I'd imagine it would be very difficult, and would require a relatively powerful MCU. Ben Eater's made a few videos discussing how PS/2[0] and USB keyboards[1] work. USB's a vastly more complicated protocol compared to PS/2.
[0] https://www.youtube.com/watch?v=7aXbh9VUB3U
[1] https://www.youtube.com/watch?v=wdgULBpRoXk
You only need a bare minimum host controller (USB 1.1) to accept a keyboard, and hardcode everything in the firmware to assume one. A suitable MCU is pretty cheap:
https://hackaday.com/2018/11/30/new-part-day-the-twenty-five...
Looks like someone already made (at least the source) for an adapter based around that MCU family available:
https://github.com/zhuhuijia0001/ch559-usb-host
As for relative lack of availability, I think that says more about how many people want to use an old keyboard with a new computer (semi-common) vs. a new keyboard with an old computer (rare).
From your link:
I think that qualifies as "relatively powerful" when compared to a Z80 or 6502. :-)
I do agree that the lack of such adapters is due to zero market demand though.