Pin Description
| Pin Category | Pin Name | Details |
| Power | Vin, 3.3V, 5V, GND | Vin: Input voltage to Arduino when using an external power source.
5V: Regulated power supply used to power microcontroller and other components on the board. 3.3V: 3.3V supply generated by on-board voltage regulator. Maximum current draw is 50mA. GND: ground pins. |
| Reset | Reset | Resets the microcontroller. |
| Analog Pins | A0 – A5 | Used to provide analog input in the range of 0-5V |
| Input/Output Pins | Digital Pins 0 – 13 | Can be used as input or output pins. |
| Serial | 0(Rx), 1(Tx) | Used to receive and transmit TTL serial data. |
| External Interrupts | 2, 3 | To trigger an interrupt. |
| PWM | 3, 5, 6, 9, 11 | Provides 8-bit PWM output. |
| SPI | 10 (SS), 11 (MOSI), 12 (MISO) and 13 (SCK) | Used for SPI communication. |
| Inbuilt LED | 13 | To turn on the inbuilt LED. |
| TWI | A4 (SDA), A5 (SCA) | Used for TWI communication. |
| AREF | AREF | To provide reference voltage for input voltage. |
Arduino Uno Technical Specifications
| Microcontroller | ATmega328P – 8 bit AVR family microcontroller |
| Operating Voltage | 5V |
| Recommended Input Voltage | 7-12V |
| Input Voltage Limits | 6-20V |
| Analog Input Pins | 6 (A0 – A5) |
| Digital I/O Pins | 14 (Out of which 6 provide PWM output) |
| DC Current on I/O Pins | 40 mA |
| DC Current on 3.3V Pin | 50 mA |
| Flash Memory | 32 KB (0.5 KB is used for Bootloader) |
| SRAM | 2 KB |
| EEPROM | 1 KB |
| Frequency (Clock Speed) | 16 MHz |
Arduino UNO vs Nano vs Mega
| Name | Processor | Operating/Input Voltage | CPU speed | Analog In/Out | Digital IO/PWM | EEPROM / SRAM[kB] | Flash | USB | USART |
| Uno | ATmega328P | 5V / 7-12V | 16 MHz | 6 / 0 | 14 / 6 | 1 / 2 | 32 | Regular | 1 |
| Nano | ATmega328P | 5V / 7-12V | 16 MHz | 8 / 0 | 14 / 6 | 1 / 2 | 32 | Mini |
1 |
| Name | Processor | Operating/Input Voltage | CPU speed | Analog In/Out | Digital IO/PWM | EEPROM / SRAM[kB] | Flash | USB | USART |
| Mega | ATmega2560 | 5V / 7-12V | 16 MHz | 16 / 0 | 54 / 15 | 4 / 8 | 256 | Regular | 4 |
| Nano | ATmega328P | 5V / 7-12V | 16 MHz | 8 / 0 | 14 / 6 | 1 / 2 | 32 | Mini | 1 |
