Use PS/2 keyboard with 3.3v MCU

Discussion in 'Embedded Systems and Microcontrollers' started by CollieJim, Jun 20, 2013.

  1. CollieJim

    Thread Starter Member

    Nov 27, 2004
    25
    0
    Hi,

    I need to connect a PS/2 keyboard, which is a 5v device, to an FRDM-KL25Z MCU which is a 3.3v device, and would like to use the Freetronics LEVEL.

    The clock and data lines need pullups. Does it matter on which side of the level converter they go?

    Thanks,
    Jim
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    If I remember correct correct .The PS2 keyboard is I2C based. The I2C use a float high, drive low approach. So the correct thing would in this case. Will be to have pullup resistor on the same side as the signal origin.
     
  3. John P

    AAC Fanatic!

    Oct 14, 2008
    1,632
    224
    Looking at the circuit for the Freetronics product, it already has 10K pullups on both sides of the transistor that does the actual conversion, so it seems as if all you have to do is connect it up and you're ready to go. It's a clever use of components.
     
  4. CollieJim

    Thread Starter Member

    Nov 27, 2004
    25
    0
    I was hoping it would be that simple. Thanks.
     
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