#include <Adafruit_MCP23X17.h>
#include <Arduino.h>

Adafruit_MCP23X17 mcp;

void setup() {
    Serial.begin(9600);
    Serial.println("MCP23xxx Blink Test!");

    if (!mcp.begin_I2C(0x27)) {
        Serial.println("Error.");
        while (1);
    }

    for (int i = 0; i < 16; i++)
        mcp.pinMode(i, OUTPUT);

    Serial.println("Looping...");
}

void loop() {
    for (int i = 0; i < 16; i++) {
        mcp.digitalWrite(i, HIGH);
        delay(100);
    }
    for (int i = 0; i < 16; i++) {
        mcp.digitalWrite(i, LOW);
        delay(100);
    }
}