Mcp23017 - Button input example

This page contains an example of reading input from a button.

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Connections for this example

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Full example

In this example, we first include the library and create an instance of the board. Next, in the setup() function, we initialize the I2C communication with the I/O expander and set the pin mode for the GPB0 pin (which is used for the button). Finally, in the loop() function, we read the pin and print the status of the button to the Serial monitor:

#include "MCP23017-SOLDERED.h"

MCP_23017 mcp;

void setup()
{
    // Initialize MCP23017
    mcp.begin();

    // Initialize serial communication
    Serial.begin(115200);

    // Set up the buttons
    mcp.pinMode(GPB0, INPUT_PULLUP);
}

void loop()
{
    // Read the button
    if (mcp.digitalRead(GPB0) == LOW)
    {
        // Button is pressed
        Serial.println("Button is pressed");
    }
    else
    {
        // Button is not pressed
        Serial.println("Button is not pressed");
    }

    delay(1000);
}

Button state on serial monitor

mcp.begin()

Initializes the I/O extender via I2C

Returns value: None

mcp.pinMode(uint8_t pin, uint8_t mode)

Controls a single pin direction

Returns value: None

Function parameters:

Type	Name	Description
uint8_t	pin	pin number
uint8_t	mode	OUTPUT, INPUT, or INPUT_PULLUP

mcp.digitalWrite(uint8_t pin, uint8_t state)

Sets the state for a specific pin

Returns value: None

Function parameters:

Type	Name	Description
uint8_t	pin	pin number
uint8_t	state	state in which to put the pin

mcp.digitalRead(uint8_t pin)

Gets the state of a specific pin

Returns value: None

Function parameters:

Type	Name	Description
uint8_t	pin	pin number