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Topic: Logic Level Converter 3> 5 > 3 (Read 1 time) previous topic - next topic

eddiea6987

Assuming  I have some sort of 3.3v Cmos device which I must use with other 5v devices , lets say via I2C , would i simply, very crudely , just have to drop each connection of the I2C to 3.3v and step up to  5.5v when going the other way. If for some reason i just wanted to make a level converter with separate components instead of an IC designed for that purpose, I am just trying to get an idea of what is going on in there.
I could print the Arduino logo on a box of cereal and sell it as "Arduin-O's"

Grumpy_Mike

No, I2C just uses pull down signaling, so you need to only use pull up resistors to 3V3 and to change a line in the wire library to stop the internal pull ups being enabled.

Photomankc

http://www.rocketnumbernine.com/2009/04/10/5v-33v-bidirectional-level-converter

If you want true level shifted bi-directional coms that circuit will do it for you.  The chances are that the 3.3v signals will trigger the 5v side just fine but I like that circuit, it's simple and effective.  Made up a few little PCBs that can breadboarded easily and have two channels each.  Perfect for I2C. 

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