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By micropuller
Am I correct in understanding that when I want to use and i2c device together with a pro micro, I have to hook it up to pins D2 and D3 instead of the usual A4 and A5, which aren't broken out on this board?
So when I want to use an i2c device, I have the same number of remaining analog pins and two less digital pins compared to when using an arduino pro mini?
By derricka
For i2C connections to Sparkfun Pro Micro or Arduino Micro, physical wiring is as follows:

SDA connects to Arduino Micro pin Labeled 2 (not A2)
SCL connects to Arduino Micro, pin Labeled 3 (not A3)
GND connects to GND

POWER: i2C devices usually require power. Pins may be labeled VCC, 5V or 3V. (*** BE CAREFUL HERE ***) This may be connected to Arduino Micro under the following conditions.
1) The i2C device consumes less current (ma) ,at all times, than your Arduino can provide.
2a) The i2C device consumes the same voltage that your Arduino provides.
2b) The i2C device consumes the less voltage that your Arduino provides, but has an added regulator that lowers the voltage to the correct level. Here's a trick: Place three 1N4007 diodes in series, to drop 5V down to 3V if you don't have a proper regulator on hand.
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