#define R_PIN 13
#define R_DELAY_MS 300

void setup()
{
    pinMode(R_PIN, INPUT);
    Serial.begin(9600);
}

void loop()
{
    Serial.print("millis=");
    Serial.print(millis());
    Serial.print("\tvalue=");
    Serial.print(digitalRead(R_PIN));
    Serial.print("\n");
    delay(R_DELAY_MS);
}