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Topic: Interfacing Arduino with 3.3V Parallax Propeller (Read 1 time) previous topic - next topic

fj604

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?

fj604

Hi Richard,

Thanks for your reply - this will stop me from looking for cheap solutions for this :)

fj604

#2
Dec 11, 2010, 07:59 pm Last Edit: Dec 11, 2010, 08:01 pm by fj604 Reason: 1
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?

PaulS

Quote
Is it safe to connect Arduino ground to Propeller ground if they are powered by different sources?

Safe and essential.

fj604

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.

PaulS

Quote
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.

fj604

I have tested it with two a voltage divider (2 x 11k resistors) on 5V input to Propeller - and it works :)

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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