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5v inputs or outputs with a 3.3v prop (5 volt) — Parallax Forums

5v inputs or outputs with a 3.3v prop (5 volt)

tonyp12tonyp12 Posts: 1,951
edited 2010-09-12 15:47 in Propeller 1
The tread called 'how to safely interface 5v to the prop" seems gone.

Simple solution seems that you put a 1k resistor in series for inputs.

But if you have to use external logic anyway
like a multiplexer or shift register
There are 74VHC chips that can handle
these voltage difference for you.

http://www.fairchildsemi.com/ds/74/74VHC153.pdf

http://www.fairchildsemi.com/ds/74/74VHC595.pdf

The 74LVC seems to mix 3.3v and 5v nicely too.
http://www.nxp.com/documents/data_sheet/74LVC595A.pdf

I'm not sure if VLC or VHC is best for the prop?

The 8-to-1 mux I can only find in HC151,
How would I use that one with 5v inputs (they are from a open collector source if need to know)

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-09-12 15:46
    There's a link to that thread in the "sticky thread" called "Propeller: Getting Started and Good Thread Index" under Technical Considerations.

    Try this link
  • tonyp12tonyp12 Posts: 1,951
    edited 2010-09-12 15:47
    "Technical Considerations:"
    "How to safely interface a 5V signal to the Propeller"

    Click on it and it just brings you back to forum front page.

    Update: your link works.

    But I still would like to see a official guide about 5V interfacing.
    ,and not some random Q&A in a thread.
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