Arduino Leonardo Pinout
Find the Arduino Leonardo pinout, digital and analog pins, memory limits, and Circuitera compile/upload support. Check board-specific library compatibility.
- Processor
- ATMEGA32U4
- Clock
- 16 MHz
- Physical flash
- 32768 bytes
- Application flash
- 28672 bytes
- SRAM
- 2560 bytes
- EEPROM
- 1024 bytes
- Digital pins
- 20
- Analog inputs
- 12
- PWM
- D3, D5, D6, D9, D10, D11, D13
- Hardware UARTs
- 1
- UART pins
- D0, D1
- I2C
- D2, D3, SDA, SCL
- SPI
- MISO, SCK, MOSI, SS
- External interrupts
- D0, D1, D2, D3, D7
- Logic voltage
- 5 V
- Bootloader
- Caterina · 1200 baud USB reset
- Protocol / baud
- AVR109 · 57600
- Compile capability
- Verified · automated compile
- Upload capability
- Untested · physical hardware
- Serial capability
- Untested · physical hardware
- Simulation
- Not supported for this profile
- Build-matched compile check
- 2026-10-25
Choose the exact board
Serial is native USB; Serial1 is TTL UART on D0/RX and D1/TX. I2C uses D2/SDA and D3/SCL. SPI uses the ICSP header (Micro also exposes named SPI pins). Upload resets/re-enumerates USB; hardware validation is pending.
Compile, upload, and simulation
Real AVR-GCC compilation uses leonardo and the selected clock. Upload is experimental pending physical hardware validation. Simulation is not yet supported for this board.
Memory and signals
Application flash excludes the bootloader. SRAM use reported after Verify excludes runtime stack and heap. Check the pin reference below before connecting a circuit.
Upload and validation limits
Serial is native USB; Serial1 is TTL UART on D0/RX and D1/TX. I2C uses D2/SDA and D3/SCL. SPI uses the ICSP header (Micro also exposes named SPI pins). Upload resets/re-enumerates USB; hardware validation is pending.
No physical upload certification recorded in these build reports. Compile capability, simulated protocol tests and physical upload are separate claims.
Toolchain: avr-gcc-wasm@0.2.0. Last matching compile evidence: 2026-10-25. Build: e0f6d304cce4ae0a0989a9b1300cbc1a21a595e5e3e7f57ed0ab3468ecf7940b.
Arduino Leonardo pinout table
Every pin and alias is present in the initial HTML. Filter by signal capability, or select a pin for its existing reference details. Disconnect power before changing wiring.
38 pin entries
Select a pin to read its capabilities.
| Pin | Capabilities | Details |
|---|---|---|
| DIGITAL · UART · INTERRUPT | Serial1 RX · TTL UART, separate from native USB Serial | |
| DIGITAL · UART · INTERRUPT | Serial1 TX · TTL UART, separate from native USB Serial | |
| DIGITAL · I2C · INTERRUPT | SDA · I2C data | |
| DIGITAL · PWM · I2C · INTERRUPT | SCL · I2C clock · PWM | |
| DIGITAL | Also A6 analog input. Same physical terminal. | |
| DIGITAL · PWM | Digital input/output | |
| DIGITAL · PWM | Also A7 analog input. Same physical terminal. | |
| DIGITAL · INTERRUPT | Digital input/output | |
| DIGITAL | Also A8 analog input. Same physical terminal. | |
| DIGITAL · PWM | Also A9 analog input. Same physical terminal. | |
| DIGITAL · PWM | Also A10 analog input. Same physical terminal. | |
| DIGITAL · PWM | Digital input/output | |
| DIGITAL | Also A11 analog input. Same physical terminal. | |
| DIGITAL · PWM | LED_BUILTIN · PWM | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 18. | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 19. | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 20. | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 21. | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 22. | |
| ANALOG · DIGITAL | 10-bit analog input; Arduino digital alias 23. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D4. Not an additional terminal. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D6. Not an additional terminal. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D8. Not an additional terminal. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D9. Not an additional terminal. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D10. Not an additional terminal. | |
| ANALOG · DIGITAL | 10-bit analog input sharing D12. Not an additional terminal. | |
| SPI · DIGITAL | SPI is on the six-pin ICSP header, not Uno D11–D13. | |
| SPI · DIGITAL | SPI is on the six-pin ICSP header, not Uno D11–D13. | |
| SPI · DIGITAL | SPI is on the six-pin ICSP header, not Uno D11–D13. | |
| SPI | Core SS alias is PB0/RX LED, not a general exposed chip-select terminal. Use a free digital pin for peripheral CS. | |
| I2C · DIGITAL | Alias of D2. | |
| I2C · DIGITAL | Alias of D3. | |
| POWER | 5 V logic and supply rail. | |
| POWER | 3.3 V output; check the board current rating. | |
| GROUND | Common ground. | |
| POWER | Regulator input; consult board power limits. | |
| RESET | Active-low reset. | |
| ANALOG | External ADC reference; configure analogReference appropriately. |
Library compile results
Actual source/hash-matched results for this exact profile. A passed compile does not prove a real peripheral, motor or wiring works.
| Library | Pinned version | Result | Flash / static RAM | Test date |
|---|---|---|---|---|
| HID | 1.0 | PASS | 4614 / 187 bytes | 2026-10-25 |
| Keyboard | 1.0.7 | PASS | 5664 / 227 bytes | 2026-10-25 |
| Mouse | 1.0.1 | PASS | 4790 / 202 bytes | 2026-10-25 |
| Servo | 1.3.0 | PASS | 5898 / 191 bytes | 2026-10-25 |
| Wire | 1.0 | PASS | 6846 / 372 bytes | 2026-10-25 |
| SPI | 1.0 | PASS | 5084 / 156 bytes | 2026-10-25 |
| EEPROM | 2.0 | PASS | 4862 / 152 bytes | 2026-10-25 |
| SoftwareSerial | 1.0 | PASS | 6170 / 267 bytes | 2026-10-25 |
| LiquidCrystal | 1.0.7 | PASS | 5798 / 200 bytes | 2026-10-25 |
| DHT | 1.4.7 | PASS | 7970 / 183 bytes | 2026-10-25 |
| Adafruit Unified Sensor | 1.1.15 | PASS | 11592 / 268 bytes | 2026-10-25 |
| Adafruit GFX | 1.12.6 | PASS | 13588 / 497 bytes | 2026-10-25 |
| Adafruit SSD1306 | 2.5.17 | PASS | 17242 / 538 bytes | 2026-10-25 |
| Adafruit BusIO | 1.17.4 | PASS | 9496 / 402 bytes | 2026-10-25 |
| Adafruit NeoPixel | 1.15.5 | PASS | 6646 / 182 bytes | 2026-10-25 |
| NewPing | 1.9.7 | PASS | 5584 / 173 bytes | 2026-10-25 |
| IRremote | 4.7.1 | PASS | 14970 / 1039 bytes | 2026-10-25 |
| Keypad | 3.1.1 | PASS | 6406 / 293 bytes | 2026-10-25 |
| AccelStepper | 1.64 | PASS | 9610 / 260 bytes | 2026-10-25 |
| LiquidCrystal_I2C | 1.1.2 | PASS | 7378 / 416 bytes | 2026-10-25 |
Projects and next steps
The public tutorials are validated on Uno. Their concepts can help with this board, but wiring, pin maps, libraries and the exact profile must be reviewed and verified separately; they are not claimed as tested projects on this board.