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Arduino Leonardo pinout

Every Arduino Leonardo pin with its capabilities (digital, PWM, ADC, I2C, SPI, UART) and the wiring gotchas that bite. An UNO-shaped board whose chip has native USB — it can pretend to be a keyboard, mouse or game controller. Great for HID projects.

ATmega32u4 @ 16 MHzLogic: 5 VPro in app

Pin	Capabilities	Watch out
D0 (RX1)	DigitalUART1 RX
D1 (TX1)	DigitalUART1 TX
D2 (SDA)	DigitalI2C SDAInterrupt	I2C here, not A4
D3 (SCL)	DigitalPWMI2C SCLInterrupt	I2C here, not A5
D5	DigitalPWM
D6	DigitalPWM
D9	DigitalPWM
D10	DigitalPWMSPI SS (soft)
D13	DigitalPWMBuilt-in LED
A0	Analog inDigital
A5	Analog inDigital
5V	Power out 5V
3.3V	Power out 3.3V
VIN	Power in 7–12V
GND	Ground

Arduino Leonardo gotchas & notes

Native USB (the Keyboard and Mouse libraries work): the board can type or move the cursor on your PC.
I2C is on D2 (SDA) / D3 (SCL) — different from the UNO's A4/A5.
USB serial is 'Serial'; the TX/RX header pins are a separate 'Serial1'.
PWM on ~3, 5, 6, 9, 10, 11, 13.

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