The Wireless SD shield allows an Arduino board to communicate wirelessly using a wireless module. It is based on the Xbee modules from Digi, but can use any module with the same footprint. The module can communicate up to 100 feet indoors or 300 feet outdoors (with line-of-sight). It can be used as a serial/usb replacement or you can put it into a command mode and configure it for a variety of broadcast and mesh networking options. The shields breaks out each of the Xbee's pins to a through-hole solder pad. Included on board is a SD card slot. When using the SD Library to access the card, Pin 4 is CS and cannot be used otherwise. SPI also relies on pins 11, 12, and 13 for communication. Also on board is a switch allowing for control via USB or the microcontroller. The Wireless SD shield has an onboard switch labelled Micro and USB. This determine how the Xbee's serial communication connects to the serial communication between the microcontroller (ATmega8 or ATmega168) and USB-to-serial chip on the Arduino board. When in the Micro position, the DOUT pin of the wireless module is connected to the RX pin of the microcontroller; and DIN is connected to TX. The wireless module will then communicate with the microcontroller. Note that the RX and TX pins of the microcontroller are still connected to the TX and RX pins (respectively) of the USB-to-serial converter. Data sent from the microcontroller will be transmitted to the computer via USB as well as being sent wirelessly by the wireless module. The microcontroller will not be programmable via USB in this mode. With the switch in the USB position, the DOUT pin the wireless module is connected to the RX pin of the USB-to-serial converter, and DIN on the wireless module is connected to the TX pin of the USB-to-serial converter. This means that the module can communicate directly with the computer. The microcontroller on the board will be bypassed.