What's on the board?
1.3GHz ARM Processor with 1GB RAM, Slot to plugin a Camera,
Composite Video, HDMI 1080p, Stereo Audio Out
2 USB 3 Ports, 2 USB 2 Ports, 10/100 Ethernet,
Slot to plug-in a Display, WiFi & Bluetooth
SD Card Slot (where the OS resides) and a 40-Pin GPIO
Port to interface to all of your hardware projects!
The GPIO also includes: TX/RX (Serial), I2C, SPI
RPi Manual RPi / PICAXE ADC, (I2C)
Instructable