This is a library for the MCP23008/17 I2C and MCP23S08/17 SPI Port Expanders.
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Written by Carter Nelson for Adafruit Industries. BSD license, check license.txt for more information All text above must be included in any redistribution
To install, use the Arduino IDE Library Manager.
When using single pin operations such as pinMode(pinId, dir) or digitalRead(pinId) or digitalWrite(pinId, val) then the pins are addressed using the ID's below. For example, for set the mode of GPB0 then use pinMode(8, ...). NOTE The MCP23008 and MCP23S08 only have GPAx pins.
| MCP23x08 Pin # | MCP23x17 Pin # | Pin Name | Pin ID |
|---|---|---|---|
| 10 | 21 | GPA0 | 0 |
| 11 | 22 | GPA1 | 1 |
| 12 | 23 | GPA2 | 2 |
| 13 | 24 | GPA3 | 3 |
| 14 | 25 | GPA4 | 4 |
| 15 | 26 | GPA5 | 5 |
| 16 | 27 | GPA6 | 6 |
| 17 | 28 | GPA7 | 7 |
| -- | 1 | GPB0 | 8 |
| -- | 2 | GPB1 | 9 |
| -- | 3 | GPB2 | 10 |
| -- | 4 | GPB3 | 11 |
| -- | 5 | GPB4 | 12 |
| -- | 6 | GPB5 | 13 |
| -- | 7 | GPB6 | 14 |
| -- | 8 | GPB7 | 15 |
Some people have reported an undocumented bug that can potentially corrupt the I2C bus. It occurs if an MCP230XX input pin state changes during I2C readout. This should be very rare. For more information, see this forum post and this knowledge base article.
