MCP23017 Inputs (0x20)

#include <Wire.h>
#include <Adafruit_MCP23X17.h>

Adafruit_MCP23X17 mcp;

const uint8_t inputPins[] = {0, 1, 2, 3}; // GPA0..GPA3
const char* pinNames[] = {"GPA0", "GPA1", "GPA2", "GPA3"};

void setup() {
  Serial.begin(115200);
  while (!Serial) {
    ;
  }

  Wire.begin();

  if (!mcp.begin_I2C(0x20)) {
    Serial.println("Could not find MCP23017 at I2C address 0x20.");
    while (1) {
      delay(10);
    }
  }

  for (uint8_t i = 0; i < 4; i++) {
    mcp.pinMode(inputPins[i], INPUT_PULLUP);
  }

  Serial.println("MCP23017 ready. Inputs are GPA0-GPA3 with internal pull-ups enabled.");
  Serial.println("Connect a switch from any input pin to GND to read LOW.");
}

void loop() {
  for (uint8_t i = 0; i < 4; i++) {
    int state = mcp.digitalRead(inputPins[i]);
    Serial.print(pinNames[i]);
    Serial.print(": ");
    Serial.println(state == LOW ? "PRESSED / LOW" : "RELEASED / HIGH");
  }
  Serial.println("---");
  delay(500);
}