Introduction to Raspberry Pi

What are single-board microcomputers?
A microcomputer is a device that has the architecture of a full-fledged computer, but is different in size. Today, hundreds (!) Of various models (including Raspberry Pi clones) from dozens of manufacturers are represented on the market, and the single-board market differs significantly from the market of conventional computers, where all market shares have long been distributed among the leaders.

Microcomputers are most often created for specific tasks, they can not compete with conventional computers, yielding to them in power and convenience. But they are cheaper, simple, have a compact size and consume less energy. This makes the microcomputer an important element of mobile automated systems.

Raspberry Pi is today the most famous representative of the single-board microcomputer family. This is a fairly cheap and affordable entry-level motherboard, which can be bought in a variety of online stores. Asian producers have created a large number of clones (Orange Pi, Banana Pi and others) that can be used in their projects. And another very important advantage of Raspberry Pi is the huge community of developers involved in the development of architecture and software. A lot of books, training aids, operating systems and convenient tools have been released, greatly facilitating the beginner to start working with the system. Therefore, it is recommended to begin work with this microcontroller for those who have already become "melkovat" arduino.
What is Raspberry Pi?

Raspberry Pi is an inexpensive computer the size of a credit card that connects to a PC or TV monitor and uses a standard keyboard and mouse. Externally, the computer is a small four-layer printed circuit board with USB, HDMI and other connectors, a slot for Micro SD, as well as a GPIO pin. The case, memory card, keyboard, mouse, monitor, power supply must be purchased separately.

Using Raspbery Pi, you can learn how to program in Scratch and Python. Initially, the microcomputer was designed for use in schools and universities, so there are many software packages and even a special operating system for children.

A key feature of Raspberry is the ability to attach external devices to it and manage them using various software packages (the most popular is Python). All kinds of sensors, LEDs, motors, relays and other electronic components can be connected via GPIO pins in the same way as Arduino. Therefore, we can significantly expand the functionality of the microcomputer by creating a workstation for each particular project from it.

But even without external devices Raspberry Pi performs all the functions of a conventional desktop PC - with this microcomputer you can work on the Internet, play video and audio files, process texts, create tables. Naturally, Raspberry Pi can not compete with an ordinary PC on an equal footing - the microcomputer always works slower. But with certain not too heavy applications, the computer does an excellent job. As the basic operating system for Raspberry Pi is Linux, there are many clones adapted specifically for this microcontroller. More details about operational systems for Raspberry Pi we'll talk in a separate article.
Developers and history

The developer of the device is the British company Raspberry Pi Foundation. The first sample was submitted by David Braben in May 2011. The beginning of the production of the first batch of model B is dated January 2012. Since then, the computer has been upgraded yearly, and more advanced computers have been on sale.

History of release of models:


February 29, 2012 - the start of sales of Model V.


December 14, 2012 - the beginning of the production model Raspberry Pi "A".


July 14, 2014 - release of the third version of Raspberry Pi "B +".


February 2, 2015 - release of Raspberry Pi "2B".


November 26, 2015 - the release of a new microcomputer Raspberry Pi Zero, equipped with an unplugged GPIO connector.


February 29, 2016 - the release of the model Raspberry Pi 3, featuring a 64-bit processor, the presence of WI-FI and Bluetooth.


February 28, 2017 - upgraded version of Raspberry Pi Zero W with WI-FI and Bluetooth.

Raspberry Pi model A +

Model A + is a low-cost version of the Raspberry Pi board. The device was released in 2014 to replace the original Model A. The board is shown in the figure below.



In contrast to the previous model, A + has the following characteristics:


More GPIO outputs - now there are 40 of them.


Micro SD connector.


Reduced energy consumption - linear voltage regulators were replaced by switching regulators, and this saved energy.


Advanced audio system - the board has a separate power source with a reduced noise level.


Reduced form factor - composite audio output built-in 3.5-mm audio output, the presence of mounting holes, USB-connector is located on the edge of the board.

The pinout is shown in the figure



1, 17 contacts - power 3.3 V.

2, 4 contacts - supply voltage 5 V. Connected directly to the input voltage of the board.

3 - SDA output (one of the I2C-pins on the board).

5 - SCl (also one of the I2C outputs on the board).

6, 9, 14, 20, 25,30, 34, 39 - Earth. All grounding contacts are connected, any output that is closer to the remaining elements can be used.

7 - GPCLK0.

8 - TXD, one of 2 UART-outputs, responsible for data transfer. UART contacts are commonly used for the interconnection of Arduino and Raspberry Pi. It is important to properly connect the boards, since the Pi is powered by 3.3V, and the arduino is from 5V.

10 - RXD, output for UART, responsible for receiving data.

11, 13, 15, 16, 18, 22, 29, 3, 32, 33, 36, 37 are reserved contacts.

12 - PCM_C output, which is used in conjunction with a special PWM method. Provides direct access to memory.

19, 38 - MOSI contacts.

21, 35 - MISO contacts.

23, 40 - SCLK contacts.

24, 26 - CS0 and CS1 outputs.

27,28 - ID_SD, are reserved for I2C communication with nonvolatile memory.

The Raspberry Pi Model A + is used in projects where it is important to maintain low power consumption and where an Ethernet interface is not required.

Raspberry Pi 3 model B

Raspberry Pi model B is the most common board. In comparison with its predecessor Pi 2 Model B has a 64-bit processor ARM Cortex-A53 and built-in Wi-Fi and Bluetooth. The board has 1 GB of RAM, which is shared with the graphics system. There are a lot of ways to use the board - with their help you can create game consoles, security systems, tablets and other electronic devices.

To connect headphones and speakers, there is a 3.5-millimeter connector. There are also 4 USB-outlets, to which you can attach peripherals. Connection of various modules is carried out through 15-pin slots:


DSI - designed to connect the display;


CSI-2 - connecting the camera via the MIPI interface.

For low-level interfaces, the outputs are:


General purpose - 40 ports of input / output;


UART;


I2C;


SPI;


Power inputs and ground.

For communication, Ethernet interfaces, Wi-Fi 802.11n and Bluetooth 4.1 are used. As a hard drive, the board uses a microSD card with an operating system installed on it. The memory card is best used in 8 GB. Raspberry Pi model B uses the Linux operating system.

The device is powered by a 5 V adapter via a USB connector or power outlets. A special power switch is not on the Raspberry Pi to turn on the device, simply connect the power cable.

Raspberry Pi model Zero card

The model Zero series differs from its predecessors in smaller sizes. There are 2 types of boards of this kind - model Zero and a new version of Zero W. The second one differs only in the presence of Wi-fi and Bluetooth on board.



Specifications Raspberry Zero:


512 MB of RAM;


Single-core processor ARMv6Z ARM1176JZF-S with a clock frequency of 1 GHz;


Mini HDMI port;


2 micro USB ports, one for connecting to a computer;


Wi-Fi 802.11n;


Bluetooth 4.1

The location of the outputs and pinouts are shown in the figure. The board is equipped with 40 ports of general purpose input-output, UART, I2C, SPI, power outputs 3.3 V and 5 V and ground. It is important to note that the connector is not soldered and requires self-assembly.



The new model Zero W uses microSD, in contrast to the older model, which uses miniSD to work. A flash card is used as a carrier, its volume must be at least 2 GB. The board is powered by a 5-volt adapter via power pins or a micro-USB input.

Of the disadvantages, we can note a low execution speed in comparison with Raspberry Pi 3 model B. But in comparison with B Zero has smaller dimensions, which allows using it in miniature designs. Used Raspberry Pi model Zero in the same areas as the rest of the computers in this family. The board can be equipped with peripheral devices, power supply, screen. With the help of these microcomputers, video surveillance systems, gaming systems, and household appliances are being created. The presence of Wi-Fi and Bluetooth allows you to expand the range of applications. Simultaneously with the release of Raspberry Pi model Zero W, the company introduced a line of computer cases. The cases are equipped with a hole for the GPIO connector and camera installation.

Comparison of Raspberry Pi models

RAM
The Model A and Model A + boards have the smallest amount of memory - only 256 MB. Model B until October 2012 also had a capacity of 256 MB, after the volume was increased to 512 MB, like the Model B +. In the Raspberry Pi 3 board - the largest memory size, 1 GB.

USB ports

The Model A and Model A + boards are equipped with one USB 2.0 port, in Model B, the number of ports is increased to two, and in Model B + and Pi 3 to four. The most noticeable changes in the Raspberry Pi Zero - it has one connector 1 Micro USB OTG.
Audio Outputs

On this parameter the Raspberry Pi Zero model also differs - in this board 3,5-millimeter jack, HDMI is replaced by multichannel HD sound through HDMI.

Memory card format

For models A and B, SD / MMC / SDIO memory cards were used. All subsequent models use a microSD card.

Number of ports

Models A and B are equipped with a 26-pin GPIO connector, in the following models this number is increased to 40.

Power consumption

The most energy-efficient device is Raspberry Pi Zero - it uses only 160 mA. The highest power consumption is at the Raspberry Pi 3 board (800 mA-2.5 mA, 4 W). The first model A consumes 300 mA (1.5 W), models B, A +, B + require about 600-700 mA.

Dimensions
The smallest device is Raspberry Pi Zero, its dimensions are 65.0 x 30.0 mm x 5 mm. A little more model A +, whose dimensions are 65.0 x 56.0 mm x 12 mm. The remaining boards have approximately the same size of 85.0 x 56.0 mm x 17 mm.