[SOLVED] Reset for a 3.3V breakout board connected to an Uno

[marco_c]

I have breakout board for a component that is to the Uno using the serial port only. I need to reset the breakout board when the Uno is reset, but the mismatch in voltage levels (3.3V vs 5V) means that I can't connect the Uno reset signal directly to the breakout board.

Any suggestions for would be the easiest (cheapest and least components) way of doing this, given that there is just one signal whose level needs to be shifted?

[MarkT]

depends on the various impedances (often reset pins have internal pull-ups), so without a
datasheet it would be guesswork to say voltage divider...

[marco_c]

Here's the breakout boards https://www.sparkfun.com/products/9943

It is mounted on a UNO prototyping shield and the I/O pins are tied to start it up in MIDI mode.

[marco_c]

I did some research and 2 ways stood out as being 'quick and dirty' but workable. Simplifying factors for me are that the signal (RESET) hardly changes at all and it is only one way from 5V to 3V. The easiest ways:
- Voltage divider as already previously mentioned
- Zener diode voltage clamp on the signal

Here are some references in case anyone is interested

http://jamesreubenknowles.com/level-shifting-stragety-experments-1741
http://www.daycounter.com/Circuits/Level-Translators/Level-Translators.phtml
http://webhome.csc.uvic.ca/~mcheng/466/spring.2010/handouts/references/level-translation-techniques.pdf
http://codeandlife.com/2012/04/06/level-shifting-101/