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I got a bit confused by Sparkfun's hookup guide for this 9DoF breakout module.

It says the VDD-in on the breakout "should [get voltage] regulated between 2.4V and 3.6V", yet in their example they do not hook it up to the Arduino's 3.3V pin, but instead they use the 5V and a bi-directional logic level converter.

Do I need to use the logic level converter, or can I just hook the module up to the 3.3V pin of my Arduino Uno without damaging the breakout module?

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I might be missing the part of the hookup guide you're looking at but I can't see it being hooked up to 5V.

In the "Simple Hardware Hookup (I2C)" section they show two possiblilities a 5V Arduino hooked up via a logic level converter and a 3.3V Arduino hooked up directly. The logic level converter will need a 5V & 3.3V connection from the Arduino, but not the IMU.

  • In the second example it states "... if you have a 3.3V-operating Arduino – like the 3.3V/8MHz Pro – you can connect SDA and SCL directly from microcontroller to sensor." - is this equivalent to using the Arduino Uno's 3.3V pin? – kontur Feb 6 '15 at 10:26
  • Ah, there's two voltages to consider, to voltage to power a device and the voltage its logic runs at. It's the latter that's referred to here. Essentially at what voltage in digital communications logical HIGH is considered to be. This IMU can only tolerate digital communications (SDA & SCL) at 3.3V logic level. Your UNO can supply power at 3.3V but has a 5V logic level for its pins, the logic level converter takes 5V signals from the Arduino and converts them to 3.3V for the IMU and takes the 3.3V replys and converts them back up to the 5V level the Arduino expects. – darwinawardee Feb 10 '15 at 10:51
  • Hm, interesting. So did I understand correctly that I should not connect it straight to the 3.3V pin of my Uno? – kontur Feb 11 '15 at 7:46
  • You can safely power it from the 3.3V pin, but cannot safely communicate over SDA and SCL (or any other UNO pins) as they are at the wrong voltage. You'll need a logic level shifter to safely connect those pins. Take a look at sparkfun's logic level guide if you want to learn more about why this is. – darwinawardee Feb 12 '15 at 13:25
  • Thanks, I've since read up on it and realised I confused logic voltage and powering voltage here, as I've had never heard of logic voltage levels. :) – kontur Feb 13 '15 at 11:11

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