Arduino UNO

1. Reset Button:

Reset button is a hardware button on Arduino UNO board. On pressing reset button it stops whatever the software might be doing and start the code from an initial level.

2. Power USB:

Power USB can be used in two different ways:

• To power Arduino board via USB
• To upload code from ide to Arduino via USB        

3. TX and RX LEDs:

RX and TX pins stand for Receiving and Transmitting pins of Arduino used for Serial communication. TX and RX LED are connected to pin no 0 and 1 thus whenever the Arduino send or receive data over serial pins, the LED connected to TX and RX blinks respectively.

0 and 1 are the default RX and TX pin of Arduino although you can make your own RX and TX by using “SoftwareSerial” library.

4. Voltage Regulator:

Voltage regulator stabilize the DC voltage used by different elements of Arduino. Basically it’s a controller to control voltage supply provided from any source outside the Arduino environment. 

5. Power (barrel jack):

Arduino can be also powered via Barrel jack in case you want it to be powered directly via AC mains power.

6. Power pins(3.3V,5V,VIN,GND,RESET):

       Vin: This pin can be used in two different ways:

• You can supply voltage through this pin to board.
• You can access power from this pin if the supply voltage is provided by barrel jack.

       3.3v: Provide a 3.3 output volt.

       5v: Provide a 5 output volt.

       GND: Provide ground to your circuit. 

       Reset PIN: Reset pin is same as reset button you can set it high to start program in arduino from initial level or from start.

7. Analog pins:                      

The Arduino UNO has 6 pins from A0 to A5 for receiving analog inputs from sensors like temp and humidity. Analog pins in Arduino Uno is labeled as A0 to A5 they take analog input and convert it into digital signal for microcontroller. Analog pins return value between 0 to 1023 this is because of built in 10 bit analog to digital converter.

8. Main Microcontroller:

Microcontroller is the main processing unit where all the input/output operation is performed. Arduino UNO is a microcontroller board based on the ATmega328P from Atmel Company. 

9. ICSP Header:

If you look carefully in the image below, you would find that these pins corresponds to MISO, MOSI, SCK, Reset, VCC, GND

• MISO (Master In Slave Out) - The Slave line for sending data to the master,
• MOSI (Master Out Slave In) - The Master line for sending data to the peripherals,
• SCK (Serial Clock) - The clock pulses which synchronize data transmission generated by the master

Provide an alternative for programming the board other than USB.

10. Power Led:

The power led is an indicator which ensure that the board is in “ON” state.  

11. Inbuilt Led:

Arduino Uno is built for beginners and Arduino ensures that one can get started without an external input or output. For this Arduino provide an inbuilt LED in case you don’t have any or you don’t want to attach one. The inbuilt LED work on PIN NO 13 of Arduino board you can set PIN NO 13 to HIGH or LOW to make the led ON and OFF.                       

12. Digital I/O:

• Arduino contain 13 GPIO pins which can be used to reading digital data and writing digital data.
• Pin 0 and 1 are RX and TX pin by default which is used for receiving and transmission of data respectively. They can also be use well as GPIO pin.
• Pin numbers (3, 5, 6, 10 and 11) are PWM enabled pin which can be used as receiving digital input and giving analog output.

13. AREF Pin:

AREF refer to analog reference which is used to set an external voltage reference for upper limit of an analog input pins. By default it is 5v.