Arduino Basic Tutorial: Arduino UNO On board Components and Pinout
Description:
In Today’s article, we will discuss the Arduino UNO R3 pinout. I am writing an introduction to Arduino and wanted to explain the Arduino UNO Board. In this article, I will explain the following topic in detail
- ATmega328P
- USB port
- External input power terminal
- Reset button
- Various LEDs
- Voltage regulator
- 16MHz crystal oscillator
- Arduino UNO R3 pinout and assignment
- Digital input/output pins (0-13th pins)
- Analog output pin (3, 5, 6, 9, 10, 11th pin)
- Analog input pin (0-5th pin)
- Input voltage range
- pin load current
- pin assignment
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The external view of Arduino UNO R3 is shown below.
The schematic for the Arduino UNO R3 is publicly available on Arduino.cc official website.
ATmega328P
It’s a microcomputer.
- Operating voltage: 5V
- Flash memory: 32KB
- SRAM: 2KB
- EEPROM: 1KB
- Clock frequency: 16MHz
For detailed specifications, read the data sheet.
Arduino USB port
Arduino USB port is used to communicate with a PC. It is used to upload the sketch (program).
It is also used as a power supply via USB.
External input power terminal
A DC plug with an outer diameter of 5.5 mm and an inner diameter of 2.1 mm can be used. A voltage input in the range of 7V to 12V is required. If power is supplied from the USB port, no power connection is required.
Reset button
This Button is used to restart the Arduino UNO. Re-execute the program, if the behavior becomes unstable, press it.
Various On-Board LEDs
Arduino UNO has different LEDs having different meaning. These LEDS are used to check the status of Arduino UNO.
- ON: Lights up when power is supplied to Arduino UNO
- L: Connected to digital 13, lights up when digital 13 is High=5V
- TX: Transmit (lights up when data is being sent to the PC)
- RX: Receive (lights up when receiving data from PC)
Voltage regulator
This is a circuit for supplying voltages of 5V and 3.3V to the microcomputer.
16MHz crystal oscillator
A crystal oscillator that generates a 16MHz clock.
Arduino UNO R3 pinout and assignment
Here, we will explain the pin layout and pin assignments of the digital IO, analog output, etc. shown in the external view.
Digital input/output pins (0-13th pins)
When applying voltage, it can only output two values, HIGH (5V) and LOW (0V), and when reading voltage, it can only recognize HIGH or LOW.
Commands used: digitalRead(), digitalWrite()
Analog output pin (3, 5, 6, 9, 10, 11th pin)
Six of the digital IOs are available for PWM.
Set with pinMode().
The voltage range is 0V to 5V.
Command used: analogWrite()
Range: 0 to 255
Analog input pin (0-5th pin)
These pins can read the voltage value finely, and converts the voltage value from 0V to 5V to an integer from 0 to 1023 and reads it.
Command used: analogRead()
Range: 0 to 1023
Input voltage range
Input voltage: 6V to 20V
However, the electrolytic capacitor mounted on the board may have a withstand voltage of 16V.
Therefore, it is recommended to use it with the recommended input voltage of 12V or less.
pin load current
Maximum load on digital output pin: 20mA. It will be damaged if the load current exceed from 40mA.
Total IO pins must be less than 100mA.
Maximum load on 3.3V output pin: 50mA
Arduino right pins assignment
the below table is about the assignment of the right pins of the Arduino UNO board.
| pin name | function | ATmega328 connection destination (see schematic) |
| SCL | I2C: Used for serial communication | 28 (PC5) |
| SDA | I2C: Used for serial communication | 27 (PC4) |
| AREF | Reference potential for analog input | 21 (AREF) |
| GND | 8, 22 (GND) | |
| digital 13 | Connect to L LED, SPI(SCK) | 19 (PB5) |
| digital 12 | SPI (MISO) | 18 (PB4) |
| Digital 11 | Analog output, PWM, SPI (MOSI) | 17 (PB3) |
| digital 10 | Analog output, PWM, SPI(SS) | 16 (PB2) |
| Digital 9 | Analog output, PWM | 15 (PB1) |
| digital 8 | 14 (PB0) | |
| Digital 7 | 13 (PD7) | |
| digital 6 | Analog output, PWM | 12 (PD6) |
| Digital 5 | Analog output, PWM | 11 (PD5) |
| Digital 4 | 6 (PD4) | |
| Digital 3 | Analog output, PWM | 5 (PD3) |
| Digital 2 | 4 (PD2) | |
| Digital 1 | Tx | 3 (PD1) |
| digital 0 | Rx | 2 (PD0) |
Arduino left pins assignment
the below table is about the assignment of the left pins of the Arduino UNO board.
| pin name | function | ATmega328 connection destination (see schematic) |
| IOREF | IO pin voltage level output | |
| RESET | 1 (PC6) | |
| 3.3V output | Maximum load current: 50mA | |
| 5V output | Maximum load current: 50mA | 20 (AVCC) |
| GND | 8, 22 (GND) | |
| GND | 8, 22 (GND) | |
| Vin | External power supply | |
| analog input 0 | 23 (PC0) | |
| Analog input 1 | 24 (PC1) | |
| Analog input 2 | 25 (PC2) | |
| analog input 3 | 26 (PC3) | |
| analog input 4 | I2C: Used for serial communication | 27 (PC4) |
| Analog input 5 | I2C: Used for serial communication | 28 (PC5) |
Feel free to comment if you have any questions or concerns.
