TheBackShed.com

Forum Index : Microcontroller and PC projects : USB Keyboard

Author

Message

RicM
Regular Member

Joined: 05/02/2022
Location: Australia
Posts: 54

Posted: 03:18am 24 May 2026

Copy link to clipboard

Print this post

Dear Members,

Is it possible to use a USB keyboard with a PS2 adapter.

Kegrads,

RMab

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 03:47am 24 May 2026

Copy link to clipboard

Print this post

Some keyboards will.
The adapters don't have a converter built in, the keyboard has to do it.
Some have a dual USB / PS2 chip that detects what format it is plugged into and switch to match.
They appear to be getting less common now. I think the Microsoft basic model does but those with extra features are likely to be USB only.

vhofst

Newbie

Joined: 29/01/2024
Location: Chile
Posts: 9

Posted: 01:15am 29 May 2026

Copy link to clipboard

Print this post

RicM said Dear Members,

Is it possible to use a USB keyboard with a PS2 adapter.

Kegrads,

RMab

I try a lot of USB keyboard with usb/ps2 adapter and it works. The USB know it is connected to a ps/2 port.

But... wired usb keyboard, keyboard with usb wireless dont work for me.

Best Regards

Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 8877

Posted: 07:02am 29 May 2026

Copy link to clipboard

Print this post

It's a historical thing. When USB was still fairly new manufacturers (mostly Chinese) wanted to make keyboards and mice for the new USB-only machines but they were still selling replacement equipment for older systems. They cleverly made keyboards and mice with firmware that could test to see whether it was connected to USB or to PS2 via a cheap passive adapter. That way they could sell the same components into both markets at very little additional cost.

Many manufacturers continued this practice for years, simply not providing the adapter as the number of PS2 machines dropped and that market dwindled. As new USB-only keyboards were being designed, with additional functionality, built in USB hubs, improved rollover etc., support for PS2 was dropped. This version of the firmware was then used across almost the full range of devices.

Even now you'll find that some USB keyboards and mice still have dual functionality, but they are usually the cheap end, pretty basic devices where the manufacturer is using old firmware to keep the manufacturing cost to the bare minimum.

Going the other way, using a PS2 keyboard or mouse into a USB port can't use any sort of passive adapter, the process is too complex and requires digital processing. These intelligent adapters are available (or you can build one using a Pico!). I have a friend who is currently using a lovely old IBM Model M keyboard into a USB port of a Mac mini using such a device. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

Print this page

To reply to this topic, you need to log in.