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Dumb level-shifting question — Parallax Forums

Dumb level-shifting question

mparkmpark Posts: 1,305
in Propeller 1
I want to connect the output of a 5V chip to a Propeller input pin. I found a step-down level shifter circuit here which seems nice and simple, but being super lazy I'm wondering if I can simplify it even further: just connect output to input with a resistor. Am I a genius or an idiot? LMK.

Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    No problem, we do it all the time with a resistor and the actual value depends upon a few factors but the default value is around 3k3 or so. Smaller values are useful for higher speeds but increased source current. If you were just monitoring sense switches etc you could even go 100k or more.
  • T ChapT Chap Posts: 4,223
    A cmos 4050 is very simple too.

    The input-signal high level (VIH) can exceed the VCC supply voltage when these devices are used for logic-level conversions
  • mparkmpark Posts: 1,305
    Awesome, Peter. Thanks!
  • mparkmpark Posts: 1,305
    And thank you, T Chap! Good to know.
  • GenetixGenetix Posts: 1,754
    mpark,

    Also don't forget that there are resistor arrays which just about every Parallax board or module uses.
    Resistor arrays come in 2 versions: individual or common pin.
    A group of LEDs would use a common pin array since they will all either be connected to power or ground.

    That was not a 'dumb' question by the way. :)
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