Home
JAQForum Ver 24.01
Log In or Join  
Active Topics
Local Time 09:27 21 Nov 2025 Privacy Policy
Jump to

Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.

Forum Index : Microcontroller and PC projects : 3,3 V for the pico Ps2 keyboard

Author Message
Plasmamac

Guru

Joined: 31/01/2019
Location: Germany
Posts: 596
Posted: 06:14pm 12 Jul 2022
Copy link to clipboard 
Print this post

Hi,
I testet my keyboard with 3,3 V.
Its working with 3,3v.

Have you a keyboard which works with 3,3v ?
Anyone can confirm  and shows the brand here ?
Unfortunately my keyboard has no label in the back.
Gtx
Plasma
 
LandBoardsLLC
Newbie

Joined: 04/06/2022
Location: United States
Posts: 19
Posted: 06:48pm 12 Jul 2022
Copy link to clipboard 
Print this post

I've tried 3.3V operation with 5 or 6 keyboards. Most worked. I had 2 identical Microsoft Natural keyboards where one worked and the other didn't.

- Doug at Land Boards LLC
 
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10628
Posted: 06:50pm 12 Jul 2022
Copy link to clipboard 
Print this post

  Quote  I had 2 identical Microsoft Natural keyboards where one worked and the other didn't.


I think this is the issue. Any recommendation could not guarantee all keyboards of that make/model would behave the same.
 
phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 2832
Posted: 04:18am 13 Jul 2022
Copy link to clipboard 
Print this post

The only keyboard that I have that requires 5V power (a very old Hewlett Packard) works perfectly with the pullups going to 3.3V, so it does not need level shifters. Its a matter of testing before deciding if you can omit the level shifters.
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 8304
Posted: 06:39am 13 Jul 2022
Copy link to clipboard 
Print this post

The only reason I'd leave out the level shifter on my boards now would be for miniaturisation. As a *minimum* I'd fit 270R series resistors and Schottky diodes and parallel 10k pull-ups to 3V3 because someone, somewhere will plug in a non-standard keyboard that has its own internal pullups to 5V (as do many mice). This arrangement isn't perfect, but it will give a degree of protection.
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.

The Back Shed's forum code is written, and hosted, in Australia.
© JAQ Software 2025