MCP23017

The MCP23017 IO Expander is especially handy when working with a chip like the ESP8266 that has only limited I/O. The MCP23017 is an I2C enabled 16 I/O port chip. That means that you only need 2 pins to control the chip.

The 16 I/O lines are divided into an 8 I/O PORT A and an 8 I/O PORT B. Both can be used as input as well as output. The chip also has 2 configurable interrupts. The chip can take a Vcc from 2.7V to 5V and this is perfect for 3.3 Volt devices as the modern arduino's and the ESP8266 range.

Library pin #	Port bit	Package pin (DIP/SSOP/QFN)	Silkscreen label
0	GPA0	21	A0
1	GPA1	22	A1
2	GPA2	23	A2
3	GPA3	24	A3
4	GPA4	25	A4
5	GPA5	26	A5
6	GPA6	27	A6
7	GPA7	28	A7
8	GPB0	1	B0
9	GPB1	2	B1
10	GPB2	3	B2
11	GPB3	4	B3
12	GPB4	5	B4
13	GPB5	6	B5
14	GPB6	7	B6
15	GPB7	8	B7