| Pin | Name | Function | Type |
|---|---|---|---|
| D0 | RX | UART Receive | UART |
| D1 | TX | UART Transmit | UART |
| D2 | INT0 | External Interrupt 0 | GPIO |
| D3 | INT1/PWM | Interrupt 1 / PWM | GPIO/PWM |
| D4 | SD_CS | SD Card Chip Select | SPI |
| D5 | PWM | PWM Output | GPIO/PWM |
| D6 | PWM | PWM Output | GPIO/PWM |
| D7 | WIFI_CS | WiFi Module CS (internal) | SPI |
| D8 | GPIO | Digital I/O | GPIO |
| D9 | PWM | PWM Output | GPIO/PWM |
| D10 | SS/PWM | SPI Slave Select / PWM | SPI/PWM |
| D11 | MOSI/PWM | SPI MOSI / PWM | SPI/PWM |
| D12 | MISO | SPI MISO | SPI |
| D13 | SCK/LED | SPI Clock / LED | SPI |
| A0-A5 | ADC | Analog Input (10-bit) | Analog |
| A4 | SDA | I2C Data | I2C |
| A5 | SCL | I2C Clock | I2C |
| 5V | 5V | 5V Power Rail | Power |
| 3.3V | 3V3 | 3.3V Power Rail | Power |
| GND | GND | Ground | Ground |
| RTC | RTC | Real-Time Clock (built-in) | Internal |