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Forum Index : Microcontroller and PC projects : picomite whit ps2 keyboard 3.3 volt working
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| tenij000 Regular Member  Joined: 30/05/2025 Location: NetherlandsPosts: 51 |
made youtube short video of picomite using ps2 keyboard running on 3.3 volt pico ps2 keyboard 3.3 volt |
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phil99 Guru  Joined: 11/02/2018 Location: AustraliaPosts: 2689 |
Yes, many PS/2 keyboards will work at 3.3V, despite the specification being 5V. All except one of my keyboards can and even that one can be made compatible with 3.3V by connecting the Data and Clock lines to 3.3V via 3.3kΩ resistors and powering it from 5V. |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8055 |
Then again, there are some that will never work on anything less than 4.75V. That's still within the PS2 spec. :) {WAFFLE} We aren't particularly bothered about the high/low signal level voltages as those are more or less within spec. What we are bothered about is reverse biasing the 3V3 inputs of the Pico by putting 5V on them via pullups in the keyboard/mouse, especially while the Pico isn't powered (not even the RP2350 will stand that for long). If the keyboard will run from 3V3 then that's ideal as the 3V3 inputs can't be exceeded. Some keyboards have open collector signals. Those are OK too, we just use pullups to 3V3. If designing something that someone else is going to provide an unknown PS2 keyboard or mouse for then it's a good idea to include level shifting purely as a safety measure if your target system is 3V3. :) The best way is to avoid using a 38yr old standard for modern stuff. :) {/WAFFLE} Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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