Guru
Joined: 11/02/2018
Location: AustraliaPosts: 3409
| Posted: 10:08am 18 Feb 2024 |
As noted above many (perhaps most) PS/2 keyboards will work at 3.3V. I have only found one that wont.
I have used 6.8kΩ pulldowns with the 5V keyboard and they reduced the voltage to 3.1V
The data and clock pullups are usually current sources limited to less than 0.5mA so Schottky diodes from them to 3.3V also work.
In fact ordinary diodes will do as the datasheet voltage limits are very conservative. Others have tested Din pins to 5.0V without failure. I have had pins going to Vsys (4.8V) without issue.