These proximity sensors are based on the SI1143 chip which includes photo-diodes and driver circuitry for three LEDs. The LEDs are pulsed under software control so lots of light-sensing applications can be addressed in a very flexible manner. This is a 3.3 volt chip and power for the sensor is through the pin marked 3.3V and not through PWR pin. There is no voltage regulator on the chip so it should be powered through the 3.3 volt line when using an Arduino. The chip also includes an ambient light and infrared proximity sensor for light measurements without the LEDs.
The sensor is interfaced through I2C, using the pins marked SCL and SDA. The sketch and code require JeeLib, the JeeLabs library, for some class functions that interface I2C. These allowing using 4 combinations of pins as well as the usual SCL and SDA pins on an Arduino. The board is also JeeNode ready, for JeeNode users, just plug the board in and set the port in the sketch.
The code is well-commented to allow for a wide range of experiments with parameters for driving the LEDs and reading the photo-diodes.