Introduction to Arduino Uno

Hello Electronic enthusiasts,

Welcome to circuitdevs.blogspot.com. I am here to introduce you the most amazing development board “Arduino”. Arduino, open-source hardware and software, is so popular that everybody from beginners to professionals is using it as a brain for their circuits. I won’t go much into the history of the development of the Arduino as you can find many pages dedicated to that. Simply Arduino was first started in 2003 in Institute of Interaction Design, Ivrea, Italy to provide easy prototyping tool for students without a background of electronics and programming.

Sooner it became so popular that professionals also started using it since it provides fast prototyping and easy to program the chip. There is a huge community which develops libraries for most of the sensors and peripheral devices to make it even easier to work with Arduino.

Going into details, first, we learn about the most popular among the Arduino family, the Arduino UNO. It is built around Atmel’s ATmega328P Microcontroller. Uno has 14 Digital input/output pins, of which 6 can be used as PWM outputs, 6 analog inputs. The board can be powered by either USB or by a 7-12VDC power supply.

Microcontroller	ATmega328P
Operating Voltage	5V
Input Voltage (recommended)	7-12V
Input Voltage (limit)	6-20V
Digital I/O Pins	14 (of which 6 provide PWM output)
PWM Digital I/O Pins	6
Analog Input Pins	6
DC Current per I/O Pin	20 mA
DC Current for 3.3V Pin	50 mA
Flash Memory	32 KB (ATmega328P) of which 0.5 KB used by bootloader
SRAM	2 KB (ATmega328P)
EEPROM	1 KB (ATmega328P)
Clock Speed	16 MHz

Each IO pin can provide a maximum DC current of 40mA but recommended limit is 20mA. The total current limit for the entire board is 200mA. Exceeding these limits may burn your board, so be careful.

USB Port:
The USB port on the board is primarily used to programme the Arduino. This can also power the board.

Power Jack:
Once the Arduino is programmed the board can be powered by external power supply through the power jack. The recommended voltage of 7 to 12VDC can be applied.

VIN Pin:
The external power can also be applied through the VIN pin. The voltage should be within the limits as mentioned above.

5V and 3.3V:
These pins can provide you a regulated 5V and 3.3V to power the external components.

Analog Input Pins:
Pins marked A0 through A5 are the 6 analog inputs, which utilizes ADC. ADC means Analog to Digital converter, which is used to convert analog inputs into digital signals so the microcontroller can understand. The Arduino as 10-bit resolution means it can represent the analog voltage by 1024 digital level. Aref pin is used to give a reference voltage for the Analog inputs.

The analog pins can also be configured either as digital input or as digital output pins.

Digital Output Pins:
The Arduino pins 0 to 13 are digital I/O pins. Each can be configured either as Inputs or as outputs depending on our need. When the digital pins are configured as an output, the HIGH state gives a voltage of 5V and the LOW state gives a voltage of 0V.

When the digitals pins are configured as Input, the voltage supplied from the external devices can be varied between 0 to 5V which are converted into a digital representation of 0 or 1. To determine these states there are two thresholds

If the incoming voltage is below 0.8V it is considered as 0 and if the incoming voltage is above 2V it is considered as 1. So when connecting a device make sure that the logic levels match otherwise the result will be undefined.

PWM Pins:
Of these 14 digital IO pins 3, 5, 6, 9, 10 and 11 can be used as PWM outputs (Pulse Width Modulation). The PWM is used to control the speed of a DC motor or to dim an LED.

Interrupt:
Digital pins 2 and 3 can be used as interrupts (INT0 and INT1). When an interrupt is triggered the microcontroller jumps to execute a specific piece of the program notwithstanding the usual sequence of the program.

Serial communication:
Each Arduino board is provided with at least one serial port to communicate with computer, displays, sensors and more. Arduino Uno has one serial port on digital pins 0 and 1. The serial pins are attached to the USB port to communicate with the computer. Only one device can be used on a serial port at a time. So when the Uno’s serial port is connected to any device it won’t be available for programming, this problem can be eliminated by making any digital pins as software serial, using library SoftwareSerial. The drawback with this software serial is it requires more processing and can support the same high speed as the hardware serial.

Serial Peripheral Interface (SPI):
SPI is a serial data protocol used by the microcontroller to communicate with one or more devices. The SPI can also be used to connect two microcontrollers. In SPI communication one device will be the master (usually the microcontroller), and all other devices will be slaves. The slave select pin will determine which device the Master is currently communicating with.

SPI communication will be done on at least 3 wires

MISO (Master In Slave Out) – A line for sending data to Master device
MOSI (Master Out Slave In) – A line for sending Master data to the Slave device
SCK (Serial Clock) – A clock signal generated by Master device to sync data transmission

I2C:
Inter-Integrated Circuit commonly referred as I2C is a two-wire communication protocol. The I2C protocol is so popular that upto 255 devices can be connected with just two lines. Each device can be communicated with a unique address. The two lines of the I2C bus are SCL and SDA.
SCL – Serial clock line to sync devices with data transfer
SDA – is the data line to transfer data.

For custom circuit design or PCB design please drop a mail to ramprasadajay@gmail.com