SparkFun Forums

[megaionstorm]

How must i connect the converter to used it for I2C ?

[fll-freak]

You do not. I2C is bydirectional. The Sparkfun level converter is mono directional. You will need a different approach. Google for an I2C level converter. There are chips that do this as well as various tricks based on the voltages you are trying to convert to and from.

[megaionstorm]

http://www.sparkfun.com/products/8745

Can be used with normal serial, I2C, SPI, and any other digital signal.

???

[fll-freak]

That is indeed an issue. A simple mono-directional level converter will not work on an I2C bus. Consider adding a comment to the product page or otherwise letting Sparkfun know.

[fll-freak]

This might work: http://www.dsscircuits.com/i2c-level-converter.html

More info:
http://www.nxp.com/documents/applicatio ... N10441.pdf
http://www.kip.uni-heidelberg.de/lhcb/P ... N97055.pdf


If you tell us your exact conversion issue, we might be able to suggest a simple solution. Sometimes your parts are such that you do not need conversion.

[megaionstorm]

I want to create a communication between a atmega328 (arduino) and a p8x32a (Propeller Board), via I2C.

The Atmega328 has 5V I2C and the P8X32A 3.3V I2C.

[fll-freak]

So you need to look at the p8x32a data sheet at see if the I2C inputs are 5 volt tolerant. If they are, then you need to look at the Arduino data sheet to see if 3.3V is enough to have it consider the input high. If both conditions pass, then you do not need a logic level converter.

If either condition fails, you need to read the information I linked to in a previous post.

[megaionstorm]

And between Arduino Duemilanove and DFRduino Pro Mini 8 Mhz !

[waltr]

The two lines for I2C are never 'driven' high, its the pull-ups that produce a logic high. This means that if the 5V part's inputs will work with a 3.3V logic then just tie the pull-ups to 3.3V.

[jyoung]

You do not. I2C is bydirectional. The Sparkfun level converter is mono directional. You will need a different approach.

Incorrect. The Sparkfun LLC is unidirectional on the RX lines. The TX lines work in both directions just fine. The typical approach is to connect SCL to pin 1, and SDA to pin 6 on the breakout board.

Several quadcopter designs use the Sparkfun LLC as a 5v to 3.3v I2C converter already, and I personally use Aeroquad's design.

An example schematic that functions (I know because I have one) can be found at;

http://aeroquad.googlecode.com/svn/trun ... ematic.pdf

[fll-freak]

Very interesting. When I tried to use them on a project they did not work for me at all. Even going in one direction, the signal was rounded off so much that the receiver could not latch the data properly. Trying to reverse the direction led to no signal at all.

This now makes me curious to go back and try it again using your schematic.