What are Arduino Pins

Arduino Pins are nothing but connections end-points through which the Arduino Board can communicate with the external devices, take inputs and deliver outputs.

There are different categories of PINs which are available in the Arduino board. With different variants of the Arduino Board, the number of PINs also differ.


Below are the categories into which the PINs of Arduino UNO can be categorized. These are:

  • Power : Vin, 3.3v, 5v and GND are power-related PINS. These Pins are used to connect the power into the Arduino Board to supply power and also can be used to power external device or components connected to the Board, For example, an LED.
  • Digital : 0 - 13 are Input/Output Pins and are digital Pins. These Pins can be used for input and output connections.
  • Analog: A0 to A5 is used to feed analog input between 0 to 5v. These Pins can accept only analog voltage. If the Arduino is working on 5 V, then it will accept analog voltage in the range of 0 to 5 volts. If we supply the AREF Pin with 3.3 V, then these same analog Pin will accept a voltage range of 0- 3.3v.
  • Serial: 0(Rx), 1 (Tx) used to transmitted and receive serial data. These two Pins are used to transmit or receive serial data.
  • AREF: This Pin provides a reference voltage for input voltage. This Pin is useful when we want to work with a customized external voltage
  • SPI: 10,11,12 and 13 are used for Serial communication. Serial Peripheral Interface, Pins can be used when the Arduino/ Microcontroller wants to communicate/transfer serial data to a peripheral device within a short distance.
  • PWM: 3, 5,6,9,10,11 provides an 8-bit PWM output. These Pins provides Pulse Width Modulation.
  • Reset: Reset, to reset the microcontroller. This will restart the microcontroller, and the program execution inside it will start from the beginning.
  • External Interrupt: 2, 3 is used to trigger an external interrupt.

How do We Use Arduino Pins?

Arduino Pins can be used simply like we plug in laptop charger into our laptop. That means one has to know which Pins are for what. Then one can use the Pins.

It should be noted that no Pins in the Arduino is dedicated to uploading programs into it. Programs can be only uploaded through the USB port which is integrated into your board. Don't worry about that.

How do we use Power Pins?

GND is a reference usually. When we connect our positive terminal into the (+) into 5 V Pin suppose, then the (-) terminal has to be connected to GND and vice versa. But due to the presence of diodes, the GND will provide minus (-) by default.

How do we use Analogue Input Pins?


Simple, just connect the input such as sensor input into any of the Analog Pin you want to use.

Example : Suppose, we have a LM35 Sensor, which is a temperature Sensor. It has three pins- IN-OUT-GND. So, what we will do is, we shall connect:

IN-pin into our Arduino Power Pin. (5v as 3.3v will be less for LM-35)

OUT-pin into our Arduino Analog Input (A0 to A5, Anyone we want to use)

GND into our Arduino Power PIN. (GND).

There are different sensors, but the basic configuration of connections will be almost same.

How do we use the Digital Pins?

A digital Pin (from Pin 1 to Pin 13) can accept or output values either 0v or 5v.

  • 0 Volt output/ input means a LOW.
  • 5 Volt input/output means a HIGH.

How to use the PWM Pins?

See, we don't have Analog output Pin. That is why, there is a concept of Pulse Width Modulation(PWM) in the Arduino, using which we can convert some Pins which are Digital Pins by default, to behave like Analog. And so, we can get Analog output.

See above which are the PWM Pins in Arduino Uno.

How do We use the AREF Pin?

We can use this Pin to directly feed external voltage into the Arduino. This is used when we want an analog input in the range of 0 to 3.3 volts or else. That time, we may feed the desired voltage into the AREF pin.

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