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Author Topic: Interfacing Arduino with 3.3V Parallax Propeller  (Read 1410 times)
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Hi all,

I would like to use the Parallax Propeller Demo Board as an video controller for Arduino. The Propeller chip uses 3.3V logic - what is the safe way to interface it with 5V Arduino? Is it just a matter of adding a 1K resistor between Arduino output and Propeller input?
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Hi Richard,

Thanks for your reply - this will stop me from looking for cheap solutions for this smiley
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Richard,

Thank you for pointing me to the right direction:

http://en.wikipedia.org/wiki/Voltage_divider

Is it safe to connect Arduino ground to Propeller ground if they are powered by different sources?
« Last Edit: December 11, 2010, 02:01:31 pm by fj604 » Logged

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Is it safe to connect Arduino ground to Propeller ground if they are powered by different sources?
Safe and essential.
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I checked - 3.3V to 5V direction works without any additional components such as BSS138 - Arduino properly sees 3.3V as HIGH.

For the 5V to 3.3 direction I will add a voltage divider with two 10K resistors.
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For the 5V to 3.3 direction I will add a voltage divider with two 10K resistors.
Check whether this is really necessary. Many 3.3V devices are 5V tolerant of input signals.
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I have tested it with two a voltage divider (2 x 11k resistors) on 5V input to Propeller - and it works smiley

The Propeller chip does not like 5V input at higher currents - it can get warm:

http://forums.parallaxinc.com/forums/default.aspx?f=25&m=124837

Thanks to everyone for suggestions.
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