The Centipede Shield uses the Wire I2C interface on analog pins 4 and 5 to provide 64 general purpose I/O pins. Any pin can be configured for input or output. The shield uses four Microchip MCP23017 16-pin digital I/O expander chips.

By default, the power for all chips on the Centipede Shield is drawn from the Arduino 5V bus. This is selected by the PWR jumper, shorting the 5V position. If a large number of loads will be powered by the Centipede Shield output pins, such as a large number of LEDs, then it may be necessary to use an external power source to prevent damage to the Arduino 5V regulator or the computer’s USB port.

The Centipede Shield uses the official Arduino designation of I2C pins, namely the alternate functions of Analog 4 and 5 on the original Arduino pin configuration. While the Centipede Shield is in use, the analog input functions of Analog 4 and 5 cannot be used.

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Arduino macetech Centipede Shield Pinouts

				AREF
				GND
				D13 / SCK
				D12 / MISO
RESET				D11/MOSI~
3.3V				D10 / SS ~
5V				D9 ~
GND				D8
GND
VIN				D7
				D6 ~
A0				D5 ~
A1				D4
A2				D3 ~
A3				D2
A4				D1 / TX
A5				D0 / RX