Arduino UNO- Thorough free hardware board scan

Arduino I2C bus

Since it was launched on the market the plate Arduino UNO, a lot has evolved this board with the output of its latest revisions. In addition, its same creators have rushed to create other similar plates in different formats to cover more needs than those initially covered by the UNO. Many others have even dared to create their own clone or compatible boards, although not with the same success.

Before the appearance of Arduino already there were other similar projects, such as the famous Parallax boards with Microchip PIC microcontrollers that could be programmed very easily using languages ​​such as PBASIC among others. An example of this is the Parallax Basic Stamp 2. But the fact that they were not free hardware meant that they did not have the same roots in the market as the Arduino project has had. The Italian plate has really been a revolution in this sense.

What is Arduino UNO Rev3?

Arduino logo

Arduino UNO Rev3 is the latest revision that exists at the moment of this plate. It is a small electronic board with a programmable microcontroller on its PCB. In addition to said chip, it also includes a series of pins as inputs and outputs that can be used by programming the chip to do different things. In this way, electronic projects can be created very easily.

This plate arises from the arduino project, an Italian project started in 2005 that focused on developing open hardware and software for students mainly. The first designs were directed for an institute in Ivrea, in Italy. At that time the students of this educational center used the famous BASIC Stamps that I have already mentioned above. These had a considerable cost, and they weren't that open.

Before all that, Hernando Barragán had created a development platform called Wiring, a project inspired by the famous Processing programming language. With this as a basis, they went to work to develop low-cost and simple tools for students. So they set about creating a hardware board with a PCB and a simple microcontroller, as well as creating an IDE (Integrated Development Environment).

As Wiring already used a board with an ATmega168 microcontroller, the following developments followed in the same orientation. Massimo Banzi and David Mellis would add support ATmega8 for Wiring, which was even cheaper than version 168. And so the first germ of what is today arises Arduino UNO. The Wiring project is then renamed Arduino.

The name of the famous project originated in a bar in Ivrea, where the founders of the project met. The bar was called Bar di Re Arduino, which in turn was named after Arduino from Ivrea, king of Italy until 1014.

Given the potential of these plates, more support was added from the community to move forward and create more plates. In addition, providers of electronic components and manufacturers began to design specific products compatible with Arduino. As is the case with Adafruit Industries. From here arose numerous shields and additional modules for these plates.

Faced with the overwhelming success, it was also generated the Arduino Foundation, to continue promoting and grouping the efforts of the Arduino project. A model similar to other similar organizations such as the Linux Foundation, the Raspberry Pi Foundation, RISC-V Foundation, etc.

As of this point, many Arduino variants have been spawned, with different form factors and diverse microcontrollers, as well as many accessories that we have discussed in this blog:

Detailed information of Arduino UNO

This plate Arduino UNO It has some characteristics that make it unique, and it has a series of differences with respect to other Arduino boards that we are going to highlight.

Technical characteristics, scheme and pinout

Arduino Pinout

El pinout and technical characteristics of the board Arduino UNO Rev3 They are important to know how to use it properly, otherwise you will not know the limits and the correct way to connect all the electronic components to their available pins and buses.

Starting first with her CARACTERISTICS, you have:

  • Atmel ATmega328 microcontroller at 16 Mhz
  • Onboard SRAM memory: 2KB
  • Integrated EEPROM memory: 1 KB
  • Flash memory: 32 KB, of which 0.5 KB are used by the bootloader, so they cannot be used for other purposes.
  • Chip working voltage: 5v
  • Recommended supply voltage: 7-12v (although it supports 6 to 20v)
  • Continuous current intensity: 40mA for I / O and 50mA for the 3.3V pin.
  • I / O pins: 14 pins, of which 6 are PWM.
  • Analog pins: 6 pins
  • Reset button to restart the execution of the program loaded in memory.
  • USB interface chip.
  • Oscillator clock for signals that need rhythm.
  • Power LED on PCB.
  • Integrated voltage regulator.
  • Price around € 20.

As for pins and connections available on the plate Arduino UNO:

  • Barrel Jack or DC Power Jack: is the board connector Arduino UNO to be able to power it electrically. The card can be powered by a suitable jack and by an adapter to supply 5-20 volts. If you are going to connect a large number of elements to the plate, it is likely that you will have to overcome the 7v barrier to be sufficient.
  • USB: the USB port is used to connect the Arduino board to the PC, that way you can program it or receive data from it through the serial port. That is, basically it will help you to load your Arduino IDE sketches into the internal memory of the microcontroller so that it can execute it. It can also fulfill the power function for the hob and the elements connected to it.
  • VIN Pin: you will also find a VIN pin that allows you to power the board Arduino UNO using an external power supply, if you don't want to use the USB or the above Jack.
  • 5V: supplies a voltage of 5V. The energy that will reach it comes from one of the three previous cases by which you can power your plate.
  • 3V3: this pin allows you to feed 3.3v and up to 50mA to your projects.
  • GND: it has 2 ground pins, to connect the ground of your electronic projects to them.
  • Reset: a pin to reset by sending a LOW signal through it.
  • Serial port: It has two pins 0 (RX) and 1 (TX) to receive and transmit TTL serial data respectively. They are connected to the microcontroller on their USB-to-TTL pins.
  • External interruptions: 2 and 3, pins that can be configured to trigger interrupts with a rising, falling edge, or a high or low value.
  • SPI: the bus is on pins marked 10 (SS), 11 (MISOI), and 13 (SCK) with which you can communicate using the SPI library.
  • A0-A5: are the analog pins.
  • 0 13: are the digital input or output pins that you can configure. A small integrated LED is connected to pin 13 that if this pin is high it will light up.
  • TWI: supportschannels TWI using the Wire library. You can use pin A4 or SDA and pin A5 or SCL.
  • AREF: reference voltage pint for analog inputs.


Being an open source board, not only you will find the datasheet as in the case of many other electronic products. You can also download many other documents and electronic diagrams that will help you understand how this board works. Arduino UNO internally and even build your own Arduino implementation yourself. For example, you have at your disposal the following official information:

Differences with other Arduino boards

Arduino boards

Arduino UNO Rev3 it is the ideal plate for all those who start to use this type of plates. What's more, there are starter kits to get started with everything you need included. This kit not only includes a large number of electronic components to start practicing, but also a very detailed manual to help you in each step.

However, there are other versions or formats of Arduino board which are very useful for other more advanced applications or to implement a project where size matters. The main differences between plates They are mainly in the type of integrated microcontroller, some being somewhat more powerful and with more memory to include much more sophisticated sketches or programs, and the number of pins available. But if we compare the three best-selling boards, the differences are as follows:

  • Arduino UNO Rev3: see section with technical characteristics.
  • Arduino Mega: the price rises above € 30, with dimensions somewhat larger than the UNO plate. In addition, it includes a more powerful ATmega2560 microcontroller that also works at 16Mhz, but has 256KB of flash memory, 4KB of EEPROM, and 8KB of SRAM for more complex programs. In addition, it also has more pins, with 54 digital I / O, 15 PWM, and 16 analog.
  • Arduino Micro: stands out for its small size, being smaller than the UNO, although of a similar price. In this small space, it integrates a smaller ATmega32U4 microcontroller, but which also works at 16Mhz. The memory is equal to that of UNO, with the exception of the SRAM, which has 0.5KB more. The pins have also been increased despite the small size, with 20 digital, 7 PWM and 12 analog. Another difference is that it uses micro-USB for its connection instead of USB. Being so small it is not compatible with shields or shields like the previous two ...

Arduino IDE and programming

Screenshot of Arduino IDE

To program Arduino, in any of its versions, you have available the IDE or development environment called Arduino IDE. It is compatible with both macOS, Windows and Linux. It is a free and open source suite that you can download from this link. With it you can create the codes to program the microcontroller chip on the board and thus make your projects work.

The platform is supported by an Arduino programming language that is based on the high-level programming language Processing, which in turn is similar to the well-known C ++. That is why they will have a similar syntax and way of acting.

You can know more about how to use Arduino IDE with the articles on this blog that explains how to integrate each electronic component or module with the board, or directly download the programming course Arduino IDE in PDF for free. With it you will learn the syntax and the programming language to start with your projects ...

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