Interfacing Arduino with 3.3V Parallax Propeller

Forum 2005-2010 (read only) Hardware Interfacing
1

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?

2

Hi Richard,

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

3

Richard,

Thank you for pointing me to the right direction:

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

4

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

Safe and essential.

5

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.

6

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.

7

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

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.