Hardware Reference
In-Depth Information
Chapter 2
MCP23017 GPIO Extender
Microchip's MCP23017 provides 16 additional GPIO pins that can be purchased for as
little as $1.99. The chip communicates using the I2C bus. (The companion MCP23S17 is
available for SPI bus.) The I2C bus allows the chip to be remote from the Raspberry Pi,
requiring only a four-wire ribbon cable (power, ground, and a pair of I2C bus lines). This
chapter explores the features and limits of this peripheral.
DC Characteristics
When shopping for chips or interface PCBs based on a particular chip, the first thing I
look at is the operating supply voltage. 5 V parts are inconvenient for the Pi because of its
3.3 V GPIO interface. Many newer devices operate over a range of voltages, which include
3.3 V. The MCP23017 supply V
DD
operates from an extended range of +1.8 V to +5.5 V. This
clearly makes it compatible, if we power the chip from a +3.3 V source. Figure
2-1
shows
the MCP23017 chip pinout diagram.
