Arduino - A0 는 14 번

https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/variants/standard/pins_arduino.h#L56

A0~A7 순서로 14~21 이다.

#define PIN_A0   (14)
#define PIN_A1   (15)
#define PIN_A2   (16)
#define PIN_A3   (17)
#define PIN_A4   (18)
#define PIN_A5   (19)
#define PIN_A6   (20)
#define PIN_A7   (21)

static const uint8_t A0 = PIN_A0;
static const uint8_t A1 = PIN_A1;
static const uint8_t A2 = PIN_A2;
static const uint8_t A3 = PIN_A3;
static const uint8_t A4 = PIN_A4;
static const uint8_t A5 = PIN_A5;
static const uint8_t A6 = PIN_A6;
static const uint8_t A7 = PIN_A7;