MicrocontrollersQUICK REFERENCE
Arduino Uno R3
The classic 5 V board: pins, power and the three essential buses.
01Pin map
- Digital
- D0–D13; A0–A5 also work as digital I/O.
- PWM ~
- D3, D5, D6, D9, D10, D11; analogWrite: 0–255.
- Analog
- A0–A5; 10-bit ADC: 0–1023; default reference = supply.
02Communication
- I2C
- SDA = A4; SCL = A5. Dedicated SDA/SCL headers duplicate these pins.
- SPI
- COPI/MOSI = D11; CIPO/MISO = D12; SCK = D13; typical CS = D10. Also on ICSP header.
- UART
- RX = D0; TX = D1. Shared with USB serial; disconnect conflicting devices when uploading.
03Power & setup
- Supply
- USB 5 V or recommended 7–12 V at barrel jack / VIN.
- Headers
- 5V, 3.3V, GND, VIN, RESET, AREF; 3.3 V output is limited to 50 mA.
- GPIO budget
- Design for 20 mA or less per pin and respect total chip/port limits.