The Arduino Uno (based on the ATmega328P microcontroller) has the following pin configuration for digital and analog I/O:

Digital Pins:
Total: 14 pins (labeled D0 to D13).

• 6 pins can be used as PWM outputs (marked with ~): D3, D5, D6, D9, D10, D11.
• 2 pins support hardware interrupts: D2 (INT0) and D3 (INT1).
• Serial communication: D0 (RX) and D1 (TX) for UART.

Analog Pins:
Total: 6 pins (labeled A0 to A5).

• These can read analog voltages (0–5V) via the 10-bit ADC (1024 values).
• Can also be used as digital I/O (if needed, addressed as D14 to D19).

Other Pins:
Power Pins:

5V, 3.3V, GND, VIN (input voltage).

Special Pins:

• AREF (Analog Reference voltage input).
• Reset (D0) – Can be used to reset the MCU.

Summary Table

Example Uses
1. Digital:

• Read buttons/switches (digitalRead()).
• Control LEDs/relays (digitalWrite()).

2. Analog:

Read sensors (potentiometers, LDRs) (analogRead()).

3. PWM:

Dim LEDs, control servo motors (analogWrite()).

Important Notes

• A4 (SDA) and A5 (SCL) are also used for I²C communication.
• Avoid using D0/D1 if using serial (UART) communication.