Unit V - IoT

 

Unit V

Raspberry Pi Basics

 

·       Raspberry Pi is one of the best smaller computing boards available in the market.

·       It could be used for a variety of applications like creating simple digital documents, learning programming, gaming, developing a temperature sensor, as a learning tool for the visually impaired or augmented reality systems

·       This is what the Raspberry Pi is.

·       It is a single board computer, measuring 85.60 mm × 56 mm × 21 mm, with its own ARM processor, RAM, several other ports and peripherals and GPIO (general-purpose input−output) pins that facilitate the connection of electronic components (Fig. A2.1).

·       Raspberry Pi was first released in the year 2012.

Architecture

·           The first-generation Raspberry Pi uses Broadcom BCM2835 SoC (System on Chip) hardware, while the second-generation comes with BCM2836

·         Figure A2.3 depicts top view of Raspberry Pi.

 

 

Figure A2.3 Top view of Raspberry Pi indicating the components.

The components are described as follows:

1.       The Processor:

·       All the models of the first generation make use of a 32-bit, 700 MHz, single core chip that uses the ARM11 architecture.

·       Raspberry Pi 2, has a much improved processor. It works with a 32-bit, 900 MHz, quad core ARM Cortex-A7.

·       This processor is based on ARM v7-A architecture.

·       The quad core processor of the second generation helps in increasing the speed by four times than that of the original generation.

·       The SDRAM used has been upgraded in each model.

·       The first-generation model A uses a 256 MB RAM, while in model B and B+ it is 512 MB. The second generation has a 1 GB RAM.

 

2.       USB 2.0 Ports:

·       Raspberry Pi model A has one single USB port, while model B has 2 USB ports.

·       Raspberry Pi model B+ and Raspberry Pi 2 have four separate USB ports.

·       All devices also have a 5 V micro USB in addition.

·       Using the USB 2.0 ports, we could plug in a keyboard and a mouse to interact with Raspberry Pi.

3.       Ethernet Port:

·       Except model A, all other models are built with a 10/100 RJ45 Ethernet port.

·       10/100 signifies that the devices are compatible with the speeds 10 Mbps and 100 Mbps, respectively. I

·       t is also possible to access the Internet using model A by connecting a Wi-Fi dongle into one of its USB ports.

·       Ability of the Raspberry Pi to access the Internet is a great feature that facilitates it to be used in several smart system designs.

4.       SD Card Slot:

·       None of the Raspberry Pi models have a hard disk for memory storage.

·       There is a memory card slot into which the user can insert the memory card.

·       Raspberry Pi models A and B are compatible with SD (Secure Digital) card, MMC (Multi Media Card) and SDIO (Secure Digital Input Output) card.

·       The memory card is loaded with the OS for Raspberry Pi. (Refer to Fig. A2.4 to have a look at the bottom view of the kit.)

 

 

 

  

Figure A2.4 Bottom view of Raspberry Pi indicating SD card slot.

5.       Analog Audio Output:

·       All the models of Raspberry Pi produce an analog audio output through a 3.5 mm audio jack provided on the device board.

·       Digital audio output is also provided by the Raspberry Pi through an HDMI port.

6.       Composite Video Output:

·       Analog video signal without the audio is called as composite video.

·       The composite video output from Raspberry Pi complies with PAL (Phase Altering Line) and NTSC (National Television System Committee) standards.

·       PAL and NTSC provide certain resolution and broadcast color standards for analog video transmission.

·       The resolution of the composite video output is lesser than that of the HDMI output.

7.       HDMI Port:

·       An HDMI (High Definition Multimedia Interface) port in all Raspberry Pi models helps in providing a visual output on a monitor or a TV screen and also in providing a digital audio output.

·       This could be brought about by the use of appropriate HDMI connectors, which maybe with HDMI to DVI (Digital Visual Interface) or HDMI to VGA (Video Graphics Array).

·       The HDMI port in Raspberry Pi can provide 14 different resolutions.

·        To connect the HDMI port to an analog TV, HDMI to RCA cables could be used which are presented in Fig. A2.5.

                                     Figure A2.5 Cables – HDMI to DVI, HDMI to RCA and HDMI to VGA.

8.    Status LEDs:

•   Raspberry Pi is equipped with a set of five different LEDs that indicate the status of the device to the user, regarding the power supply, network connectiv- ity, etc.

•   ACT (Green) – ON when SD card is accessed.

•   PWR (Red) – ON when there is 3.3 V power supply.

•   FDX (Green) – ON for full duplex LAN.

•   LNK (Green) – ON when there is network (LAN) activity.

•   100 (Yellow) – ON for 100 Mbps network connection.

9.    Power Supply: In all the models of Raspberry Pi, there is a 5 V micro USB port through which the device can be powered.

•   Raspberry Pi 2 – 4.0 W

 

10.    GPIO Pins:

·       The set of GPIO (general purpose input−output) pins on the device makes Raspberry Pi different from regular computers.

·       These pins could be connected to electrical and electronic components.

·       When Raspberry Pi is connected to the Internet, it is possible for the user to control the connected components from anywhere.

 

Compatible Peripherals, Add-Ons, and Accessories  

1.      Power Supply Cable:

·       It might seem that a mobile phone charger, consisting of a typical USB to micro USB cable, would be sufficient to power Raspberry Pi.

·       When Raspberry Pi is not fed with sufficient power, it will fail to function well.

2.      SD Card:

·       Generally, SD cards with class 4 speed are recommended for use with Raspberry Pi.

·       High-speed SD cards with poor stability do not function well with Raspberry Pi.

·       A memory of at least 4 GB is required.

3.      Camera Module:

·       A camera module could be directly connected to Raspberry Pi.

·       The camera module when connected to Raspberry Pi could be used for special effects applications like slow motion video and time lapse video, apart from taking normal photographs and videos.

·       The camera module is similar to those available on mobile phones. (Figure A2.6 shows the camera module for Raspberry Pi.)

Figure A2.6 Camera module for Raspberry Pi and camera module connected to CSI port.

4.      LCD Display:

·       To connect LCD display boards or OLED screens to Raspberry Pi, there is a special connector called DSI (Digital Serial Interface) connector.

·        Connection is facilitated by a 15 pin flat ribbon cable.

5.      Real Time Clock:

·       Raspberry Pi does not have any built-in real-time clock in it.

·       When the user is connected to the Internet, it uses the date and time information through the online sources.

·       However, when Raspberry Pi is operates as a standalone system, without accessing the Internet, different arrangements have to be made for the device to be fed with time.

6.      Heatsink:

·       When operated under normal conditions, Raspberry Pi does not get heated up as it is meant for mobile applications

·       When overclocking is done, a heatsink may have to be added.

·       Overclocking is the process of running the processor at a speed higher than the one intended by the manufacturer.

·       The overclocking options could be enabled by a certain command line.

·       The system continues to function at the increased speed until the temperature exceeds 85oC.

·       At this point, overclocking is automatically disabled by Raspberry Pi.

Operating System for Raspberry Pi

Before understanding the operating systems supported by Raspberry Pi, let us get acquaint- ed with NOOBS (New Out Of the Box Software) which makes the OS installation process in the SD card of Raspberry Pi a simpler process.

NOOBS is an exclusive install manager for OS installation in Raspberry Pi.

NOOBS can be downloaded as a torrent or zip file from http://www.raspberrypi.org/ downloads/.

There are two versions of NOOBS – NOOBS and NOOBS LITE.

The former offers offline and network download while the latter offers only network download.

SD cards pre-installed with NOOBS are also available. After downloading NOOBS, extracting the required folders and installing it in the SD card, the SD card could be inserted into the SD card slot of Raspberry Pi.

In Raspberry Pi provided with power supply and plugged in with a keyboard and mouse, inserting an SD card will initialize the booting process. A window listing out the different operating systems compatible with Raspberry Pi would appear (see Fig. A2.8). NOOBS is extremely useful for beginners as it helps in easy OS installation without configuration process. Experienced users could also download OS without using NOOBS.

The different operating systems that could be installed using NOOBS are:

1.       Raspbian

2.       OpenELEC

3.       Pidora

4.       RaspBMC

5.       RISC OS

6.       Arch Linux ARM

All the above-mentioned operating systems make use of Linux kernel.

·        Raspbian is the most common operating system used with Raspberry Pi and is the most recommended one. Raspbian is the Debian operating system specifically designed for use with Raspberry Pi. Pidora is the Fedora Remix for Raspberry Pi. OpenELEC (Open Embedded Linux Entertainment Center) is based on Kodi (XBMC earlier) software.

 

 

Figure A2.8 NOOBS window showing OS choices available.

 

Setting up Raspberry Pi

Follow the instructions given below to set up your Raspberry Pi before you configure it or before it gets booted up. Figure A2.9 depicts a set up Raspberry Pi.

1.       Insert the SD card installed with NOOBS into the SD card slot of Raspberry Pi. An 8 GB SD card is recommended.

2.       You will require a display screen like a TV or monitor to work with Raspberry Pi.

o   Connecting your chosen display unit to Raspberry Pi via the HDMI port would give better display results.

o   If the display unit is old and is not compatible with the HDMI port, then there is an alternative video output port available (RCA port or TRRS port).

 

 

Figure A2.9 Raspberry Pi connected to various peripherals.

 

3.       To control Raspberry Pi and provide inputs to the device and give commands, you must connect a keyboard and a mouse to Raspberry Pi through its USB ports.

4.       Connect the micro USB of the Raspberry Pi to a 5 V power supply. Ensure that the device gets the required current; else the device might be underpowered.

5.       If you require Internet access when working with Raspberry Pi, connect it to the Ethernet cable via the Ethernet . Internet access is possible using a Wi-Fi dongle and connecting it to a USB port.

6.       Headphones or powered speakers could be plugged into the audio output port for sound. When there is no audio equipment in the display device, then the audio output port could be made use of.

In the above set of instructions, steps from 1 to 4 are necessary if the user wants to work with Raspberry Pi. Steps 5 and 6 are optional.

Initial Configuration for Raspberry Pi

Raspberry Pi configuration tool (Fig. A2.10) is called as “Raspi-Config”. The configuration menu offers the following options:

Figure A2.10 The Raspi-C

1.       Expand File System: Using NOOBS to install OS automatically expands the file system. File system enables the installed files to occupy entire SD card, thus making the entire SD card available for Raspberry Pi.

2.       Change User Password: The default username is “pi” and the default password is “raspberry”. This option allows to change the password.

3.       Enable Boot to Desktop/Scratch: This option helps the user to decide what he/she wants after booting takes place, that is, if the device should boot into the desktop or command line or Scratch.

4.       Internationalization Options: Selecting this option and pressing enter key provides the following setting options to the user:

a.   Change locale.

b.   Change time zone.

c.   Change keyboard layout.

5.       Enable Camera: This option should be selected if the user would like to use the camera module.

6.       Add to Rastrack: Rastrack is a Google-Map based application developed which indicates all Raspberry Pi users on a heat map based on their location. Selecting this option adds the user to the map.

7.       Overclock: Selecting this option lets the user to use the processor at a speed higher than its processor speed.

 

Advanced Options

1.   Overscan: When we enable overscan a black border around the screen is formed, so that none of the initial text leaves the screen. If overscan is not enabled, the entire image is made to fit the entire screen and better resolution is obtained.

2.   Hostname: This option enables the user to assign a name to his/her device (Raspberry Pi) for identification when connecting to the Internet.

3.   Memory Split: This option helps the user to fix the RAM memory to be allowed for the GPU for graphics and multimedia.

4.   SSH (Secure Shell): It helps in accessing the command line of Raspberry Pi from another computer, when connected to the Internet.

5.   Device Tree: It allows for effective management of allocation of resources and auto-configuration of certain modules.

6.   SPI: This configuration option helps to enable or disable the SPI (Serial Peripheral Interface) bus and related kernel modules from loading automatically.

7.   I2C: This configuration option helps to enable or disable the I2C (Inter-IC) bus and related kernel modules from loading automatically.

8.   Serial: This option helps to enable or disable the messages from kernel and shell on the serial connection.

9.   Audio: This menu in the configuration window helps to select either the HDMI port or analog audio output port.

10.   Update: This option enables or disables updates to latest version.

At the end of the configuration process, a message appears asking if the system should reboot. There are some configuration settings which when enabled or disabled would require a system reboot for them to be applied.

If the user wants to access the configuration tool, Raspi-Config, after the first booting, the instruction to be typed in the command line is

 

sudo raspi-config

When in the command line, graphical interface can be accessed using the command startx.

 

Shutting Down Raspberry Pi

Raspberry Pi has no specific power button on the device. So, different shutdown schemes for the graphical desktop environment and the command prompt environment have been developed.

When using graphical interface, shutdown option can be selected from the logout menu on the desktop.

With command prompt, the following command works for shutdown:

sudo shutdown –h now

Indiscriminately disconnecting the power chord is not advisable. This might even corrupt the SD card.

Linux Based Softwares in Raspberry Pi

The following are the Linux based software available in Raspberry Pi.

1.       The File Manager (found in Accessories menu).

2.       Midori (Web browser).

3.       Omxplayer (Video and Audio).

4.       Leafpad, Nano (Text editors).

Table A2.1 presents the features of various Raspberry Pi versions available in the market along with the cost.

 

Table A2.1 Summary of Raspberry – Pi kits and corresponding features
Pi Zero	Pi 1 Model A+	Pi 1 Model B+	Pi 2 Model B	Pi 3 Model B
1 GHz 32-bit Single Core processor	700 MHz 32-bit Single Core processor	700 MHz 32-bit Single Core processor	900 MHz 32-bit Quad Core processor	1.2 GHz 64-bit Quad Core processor
512 MB RAM	512 MB RAM	512 MB RAM	1 GB RAM	1 GB RAM
Broadcom VideoCore IV GPU	Broadcom VideoCore IV GPU	Broadcom VideoCore IV GPU	Broadcom VideoCore IV GPU	Broadcom VideoCore IV GPU

 

Table A2.1 Summary of Raspberry – Pi kits and corresponding features—Continued
Pi Zero	Pi 1 Model A+	Pi 1 Model B+	Pi 2 Model B	Pi 3 Model B
2 micro USB ports	1 micro USB ports	1 micro USB ports	1 micro USB ports	1 micro USB ports
No USB ports	1 USB ports	4 USB ports	4 USB ports	4 USB ports
1 mini HDMI port, no HDMI	1 HDMI port, no mini HDMI	1 HDMI port, no mini HDMI	1 HDMI port, no mini HDMI	1 HDMI port, no mini HDMI
1 microSD slot	1 SD/MMC slot	1 microSD slot	1 microSD slot	1 microSD slot
No dedicated audio port	3.5 mm audio out port	3.5 mm audio out port	3.5 mm audio out port	3.5 mm audio out port
No Wi-Fi, No Ethernet	No Wi-Fi, No Ethernet	No Wi-Fi, Ethernet via USB Adapter	No Wi-Fi, Ethernet via USB Adapter	Onboard Wi-Fi Ethernet port
No Bluetooth	No Bluetooth	No Bluetooth	No Bluetooth	Bluetooth 4.1
65 ´ 30 mm (Half of Standard Pi Size)	85.60 ´ 56.6 mm (Standard Pi Size)	85.60 ´ 56.5 mm (Standard Pi Size)	85.60 ´ 56.6 mm (Standard Pi Size)	85.60 ´ 56.6 mm (Standard Pi Size)
$5	$20	$25	$35	$35

 

Application Development with Raspberry-Pi – A Quick Walk Through

Like most of the boards, Python is supported programming option with Raspberry – Pi too.

Raspberry Pi provides an excellent environment for learning Python as well as executing real-time applications using Python. Raspberry Pi has the Python development application IDLE.

The main goal of the Raspberry Pi Foundation was to make programming a fundamental part of regular computing. Visual programming is another interesting attribute of Rasp- berry Pi. Raspberry Pi offers Scratch as a visual programming platform. It can be used to create animations and games without actually writing a code. Figure A2.11 shows the Scratch window.

 

 

Figure A2.11 Scratch Window.

 

A2.8.1 Application − Web Lamp

This application demonstrates the use of the GPIO pins and how devices connected to Rasp- berry Pi can be controlled over the Internet. This application uses Python and Flask. Flask is a web framework which helps in tweaking Raspberry Pi into a dynamic web server. Here, Flask is used with Python libraries to make the web server more functional. This application will require a Raspberry Pi board, breadboard, power switch tail II relay, female to male jumper wires and hookup wires.

Hardware Setup: Using hookup wires, the “+in” terminal of the power switch tail is connect- ed to pin 25 of Raspberry Pi and the “−in” terminal is connected to the ground bus of the Raspberry Pi. A lamp is plugged into the power switch tail. A second AC equipment could also be controlled along with the lamp by using another power switch tail and connecting it to pin 24.

In the home directory, create a new directory and name it “WEBlamp”. In this directory cre- ate a file “weblamp.py” and in this file enter the following source code:

Pins = {

24  : {‘name’:‘fan’, ‘state’ : GPIO.LOW},

25  : {‘name’:‘lamp’, ‘state’ : GPIO.LOW}

}

 

for pin in pins:

GPIO.setup(pin, GPIO.OUT( GPIO.output(pin, GPIO.LOW(

 

@app.route(“/”( def main((:

for pin in pins:

pins[pin][‘state’] = GPIO.input(pin( templateData = {

‘pins’ : pins

}

return render_template(‘main.html’,**templateData(

 

@app.route(“/<changePin>/<action>”( def action(changePin, action(:

changePin = int(changePin( deviceName = pins[changePin][‘name’] if action == “on”:

GPIO.output(changePin, GPIO.HIGH( message = “Turned” + deviceName + “on.”

if action == “off”:

GPIO.output(changePin, GPIO.LOW(

message = “Turned” + deviceName + “off.” if action == “toggle”:

GPIO.output(changePin, not GPIO.input(changePin(( message = “Toggled” + deviceName + “.”

 

for pin in pins:

pins[pin][‘state’] = GPIO.input(pin(

 

templateData = {

‘message’ : message, ‘pins’ : pins

}

return render_template(‘main.html’, **templateData(

 

if _name_ == “_main_”:

app.run(host=’0.0.0.0’, port=80, debug=True(

 

Now, create a directory within “WEBlamp” and name it “templates”. Inside this directory, create the file “main.html” and enter the following source code in it.

 

 

 

In the terminal, go to directory WEBlamp and then start server after ensuring all other Flask servers are killed using ctrl+c. Use the command line:

pi@raspberrypi ~/WEBlamp $ sudo python weblamp.py

This application helps to control devices when away from home by staying connected via the Internet.