Pinout
ATmega328P (DIP-28) pinout
Pins
- 1 PC6 — RESET (10k pull-up to VCC)
- 2–6: PD0/RX (D0), PD1/TX (D1), PD2 (D2), PD3 (D3~), PD4 (D4)
- 7 VCC, 8 GND, 20 AVCC (tie to VCC), 22 GND, 21 AREF
- 9–10: PB6/PB7 — 16MHz crystal + two 22pF caps
- 11–13: PD5 (D5~), PD6 (D6~), PD7 (D7)
- 14–19: PB0 (D8), PB1 (D9~), PB2 (D10~/SS), PB3 (D11~/MOSI), PB4 (D12/MISO), PB5 (D13/SCK/LED)
- 23–28: PC0–PC5 = A0–A5; A4 = SDA, A5 = SCL
- The Uno chip on a breadboard — ~ marks the PWM pins
Specifications
| Core | 8-bit AVR |
|---|---|
| Supply voltage | 1.8–5.5 V |
| Clock speed | Up to 4 MHz at 1.8 V, 10 MHz at 2.7 V, 20 MHz at 4.5–5.5 V; internal 8 MHz RC oscillator |
| Flash memory | 32 KB |
| SRAM | 2 KB |
| EEPROM | 1 KB |
| I/O pins | 23 (20 usable on an Arduino-style 16 MHz build) |
| ADC | 10-bit, 6 channels on DIP-28 (8 on TQFP/QFN) |
| Timers / PWM | Two 8-bit timers, one 16-bit timer; 6 PWM channels |
| Serial interfaces | USART, SPI, I2C (TWI) |
| DC current per I/O pin | 40 mA absolute max (20 mA recommended); 200 mA total through VCC/GND |
| Operating temperature | −40–85 °C |
| Package | DIP-28, TQFP-32, QFN-32 |
Notes
- 40mA absolute maximum per I/O pin, 200mA total across VCC/GND combined — the same datasheet limit the Uno/Nano/Pro Mini above inherit from this exact chip.
- On a bare breadboard build there is no onboard regulator at all: whatever you feed VCC/AVCC IS the rail every pin’s current budget is measured against — a 9V battery through nothing but a linear regulator is a common way to accidentally starve that regulator, not the chip.
