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interfacing different serial voltage levels — Parallax Forums

interfacing different serial voltage levels

ktekxktekx Posts: 71
edited 2005-12-23 15:05 in BASIC Stamp
Can the basic stamp receive serial-in at +3v from another device that uses 3v TTL? What is the threshold minimum voltage? also, how should I go about interfacing the stamp's +5v output to the other device that uses 3v TTL, is it safe to just use current limiting resistors and leave the voltage?

Comments

  • Tracy AllenTracy Allen Posts: 6,664
    edited 2005-12-23 09:19
    The standard Stamp pins p0 to p15 have a threshold around 1.3 or 1.4 volts, so you are fine with a 3volt input level. Going the other way, it depends on the input specs of the device. Some 3 volt devices are "5 volt tolerant". If not, you will need a voltage divider or at least a resistor to interface from 5v down to 3v. You might get by with just the resistor if the other device has diode clamps at its inputs, but it is best to read the absolute maximum specs of the device.

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    Tracy Allen
    www.emesystems.com
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2005-12-23 15:05
    ktekx,

    Here is a thread that might help...

    http://forums.parallax.com/showthread.php?p=562983

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
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