Interfacing Raspberry Pi With Arduino

In this Project raspberry pi and Arduino UNO are Used. Raspberry Pi is used for sending control signals to Arduino and controlling all the activity of Arduino meanwhile the Arduino is used for sensing the o/p of LM 35 and all the other sensors which is connected with it. It is assumed that the reader has gone through the project how to get started with the arduino and How to Configure Raspberry pi.

For this I used the Raspbian ROM for raspberry. I installed pyserial into it and Arduino IDE for communicating with Arduino UNO. I’ve made connection between the Raspberry Pi and Arduino UNO with USB cable, and uploaded the scratch into Arduino named “temp.ino”. The circuit diagram of connection of LM35 and relay with Ardunio is shown in the file named “circuit connection”.

Now I have three ways to monitor the data in real time :

1) Sensing the data serially and the temperature is continuously shown on screen, temperature is updated every second. For this I’ve used following code given in the file named “dataLogger.py” .this code is in python language. For running this code through terminal, type the path where this code has been saved and then following command :

Sudo python dataLogger.py

This command will show the temperature in realtime and also generate one “.dat” file named “tempLog.dat” file.

2) Plotting the data which is stored in the “dataLogger.dat” file we have to first install the “gnuplot ” application into Raspbian using following command:

Sudo apt-get installgnuplot

Now the code for plotting the data using the “dataLogger.dat” is given in the file named “plotData.plt”

For plotting data using this code type following code in terminal :

SudognuplotplotData.plt

This command will generate the PNG file showing the plot of sensed data.

3) For plotting the sensed data in real time or for monitoring the data in realtime I have the third method. The code file for it is named “real_time_plot.py” and for use it type following command in terminal

Sudo python real_time_plot.py

This will continuously show the plot of real time sensing temperature.

The working of this project is such that whenever the temperature goes beyond the limit of 50 degree then the alarm LED will glow and the fan starts for cooling down the temperature and when the temperature is less than 40 degrees then the green LD shows the normal situation.

RaspberryPi setup

Overview :

There are many ways to setup the RaspberryPi, depending on your needs and the peripherals you wish to use. The set up process can be completed in five basic steps as shown.

Hardware features of Raspberry Pi

Basic Equipment required for general Setup :

1. Micro USB Charger (rated at 5V 700mA minimum), plus micro USB cable if needed.

2. SD Card (2Gb up to SDHC 32Gb), plus suitable card reader.

3. HDMI Cable/RCA cable for display

4. Compatible Mouse/Keyboard

5. Powered USB Hub (required for high powered USB devices)

6. Network Cable (Ethernet)

Quick Start :

• Unzip the file that you just compiled in Ubuntu:

a) Right click on the file and choose .Extract all.

b) Follow the instructions.you will end up with a file ending in .img

This .img file can only be written to your SD card by special disk imaging software, so.

• Download the Win32DiskImager software:

a) Download win32diskimager-binary.zip (currently version 0.6)

b) Unzip it in the same way you did the Raspbian .zip file

c) You now have a new folder called win32diskimager-binary

You are now ready to write the Raspbian image to your SD card.

• Writing Raspbian to the SD card:

a) Plug your SD card into your PC

b) In the folder you made in step 3(b), run the file named Win32DiskImager.exe

If the SD card you are using isn’t found automatically then click on the drop down box and select it. Then click Write. After a few minutes you will have an SD card that you can use in your Raspberry Pi.

• Booting for the first time:

a) At Raspberry pi login screen type “pi” and you will be asked for password which is “raspberry”.

b) When you see the prompt: pi@raspberry ~ $ type “startx” for a graphical environment.

Screenshot of booting and login

Getting Network Access

Overview:

For connecting RaspberryPi to network you have 3 options

1) Ethernet

2)USBtethering from your smart phone

Using Ethernet:

Connect the Ethernet Cable and open the browser and set the IP Address and proxy and get connected.

For excess internet through terminal ,type the following for setting IP

exporthttp_proxy=http://proxy IP address:port

ifconfig eth0 10.10.17.23

here10.10.17.23is the Proxy IP we used

nowPing to check the internet connection.

USB tethering:

Connect your Phone and RaspberryPi via USB cable and enable USB tethering in your device. Then open terminal and follow the steps given below for configuring your PI

1 1.Get root access by typing “sudo bash”

2.Go to the directory etc/network

3) 3.Open and file interfaces with vi command and add following lines in file

auto eth0

iface eth0 inetdhcp

iface usb0 inetdhcp

4.Save the file and type the following command in terminal for configure the changes, “ifup usb0”

5 5.Now for checking whether your Pi have been configured or not, type following

Ifconfig :

Screenshot of ifconfig

Lsusb :

Screenshot of lsusb

Overview :

We have dedicated browser in Raspberry Pi named “Midori”. So we can access internet through it using any of two method either with Ethernet or tethering.

Screenshot of various sites

Introduction to GPIO of RaspberryPi

Overview :

General Purpose Input/Output (a.k.a. GPIO) is a generic Pin on a chip whose behavior (including whether it is an input or output Pin) can be controlled (programmed) through software.RaspberryPi has broadcoms BC2835 as core which is a ARM1176JZF-S processor which supports 54 general purpose Input /Output Pin. All GPIO Pins have at least two alternative functions within BCM. RaspberryPi has pre-configured few Pins as USB, Ethernet and HDMI ports and rest 26 Pin are provided for general purpose use. The production RaspberryPi board has a 26-Pin 2.54 mm (100 mil)expansion header, marked as P1, arranged in a 2×13 strip. They provide 8 GPIO Pins plus access to I²C, SPI, UART, as well as +3.3 V, +5 V and GND supply lines. Pin one is the Pin in the first column and on the bottom row.

Image of 2×13 strip provided to use as GPIO

GPIO voltage levels are 3.3 V and are not 5 V tolerant. There is no over-voltage protection on the board. All the GPIO Pins can be reconfigured to provide alternate functions, SPI, PWM, I²C and so. At reset only Pins GPIO 14 & 15 are assigned to the alternate function UART, these two can be switched back to GPIO to provide a total of 17 GPIO Pins. Each GPIO can interrupt, high/low/rise/fall/change.

A detail image of GPIO header is given below

Pin description of GPIO

Power Pins:

The maximum permitted current draw from the 3.3 V Pins is 50 mA. Maximum permitted current draw from the 5 V Pin is the USB input current (usually 1 A) minus any current draw from the rest of the board.

Model B: 1000 mA – 700 mA -> max current draw: 300 mA

Be very careful with the 5 V Pins P1-02 and P1-04, because if you short 5 V to any other P1 Pin you may permanently damage your RasPi. Before probing P1, it’s a good idea to strip short Pieces of insulation off a wire and push them over the 5 V Pins so you don’t accidentally short them with a probe.

The other chipset GPIO Pins accessible on the PCB but are in use are:

a.GPIO16 drives status LED D5 (usually SD card access indicator)

b.GPIO28-31 are used by the board ID and are connected to resistors R3 to R10 (only on Rev1.0 boards).
c.GPIO40 and 45 are used by analogue audio and support PWM. They connect to the analogue audio circuitry via R21 and R27 respectively.
d.GPIO46 is HDMI hotplug detect (goes to Pin 6 of IC1).
e.GPIO47 to 53 are used by the SD card interface. In particular, GPIO47 is SD card detect (this would seem to be a good candidate for re-use). f.GPIO47 is connected to the SD card interface card detect switch; GPIO48 to 53 are connected to the SD card interface via resistors R45 to R50.

Extending the size of memory card (menu config)

Overview :

The default size allowed by Raspbian OS is 2 GB only , no matter whatever the size of memory card. So if we want to extend the size of it then we have to do it through “menu config”.

For doing it follow this :

Go to terminal >type this :sudoraspi-config>select this : expand_rootfs>select yes , then restart Raspberry Pi

Now you have full accessibility to your memory card. The full size of memory card will now available for storage of data.

Screenshot of expand_rootfs (menu config)

Making Arduino and RaspberryPi talk

Connection of Arduino and Raspberry Pi

Overview :

There is a Python library for serial communications called ‘pySerial‘ which allows RaspberryPi to serially communicate with Arduino using USB.

Step 1: Now load the scratch for serial transmission on Ardiuno and connect it with RaspberryPi using USB

Step 2 : Power up RaspberryPi and login
Step 3 : Browse and download pyserial-2.5.tar.gz (106.3 kB) and save it somewhere convenient. I saved it to the ‘other’ folder on the Desktop.

Step 4 : This is a gziped tar file. Which needs unzipping and untaring. To unzip it open a Terminal, which you will find from the ‘start menu’ under ‘accessories’. Now paste the following commands into it.
cd /home/Pi/Desktop/other
gunzip pyserial-2.5.tar.gz
tar – xvf pyserial-2.5.tar
Step 5 : Install pySerial, by typing these lines in your terminal window:

cd pyserial-2.5
sudo python setup.py install
Step 6 : Run Python 2. You will find this from the menu under Programming – Use Python 2

Step 7 : Now we just need to write following Python code in python 2 to access the Serial port :

import serial

ser=serial.Serial(‘/dev/ttyACM0’,9600)

while 1:

ser.readline()

This will make Pi ready to read the data transmitted serially by Ardiuno and The data will be shown on Screen as soon as you type last command.

Note : Please make sure that baudrateof both the device is same.for checking the baudrate of RaspberryPi go to file serial.py and compare the baudrate mentioned there with your baudrate if it id same it is good if not then change it with 9600 standard baubrate otherwise your evice will not talk.

Temperature sensing using RaspberryPi and Ardiuno

Overview :

For this connect RaspberryPi and Ardiuno using USB as mentioned earlier. Connect a temperature sensor with analog input of Ardiuno and load the following scratch code in Ardiuno.

Connection of LM-35 to Arduino

Ardiunosratch code:

constintledPin = 13;

constint alarmPin1 = 12;

constint alarmPin2 = 2;

constint alarmPin3 = 10;

floattempC;

int reading;

inttempPin = 5;

void setup()

{

pinMode(ledPin, OUTPUT);

pinMode(alarmPin1, OUTPUT);

pinMode(alarmPin2, OUTPUT);

pinMode(alarmPin3, OUTPUT);

Serial.begin(9600);

analogReference(INTERNAL);

}

void loop()

{reading = analogRead(tempPin);

tempC = reading / 9.31;

Serial.println(tempC);

if (Serial.available())

{

flash(Serial.read() – ‘0’);

}

if (tempC<= 50 )

{

digitalWrite(alarmPin1, HIGH);

digitalWrite(alarmPin2, LOW);

digitalWrite(alarmPin3, HIGH);

}

else

{

digitalWrite(alarmPin1, LOW);

digitalWrite(alarmPin2, LOW);

digitalWrite(alarmPin3, LOW);

}

delay(1000);

}

void flash(int n)

{

for (int i = 0; i < n; i++)

{

digitalWrite(ledPin, HIGH);

delay(100);

digitalWrite(ledPin, LOW);

delay(100);

}

And now follow the step 6 and step 7 mentioned in previous chapter

Overview :

Finally we made an application which continuously senses temperature using LM-35 temperature sensor and displays the output. Meanwhile we also plotted the previously generated temperature readings.

We have divided the overall task into 4phases :

1. First upload the above Arduino code for temperature sensing using Arduino IDE into the Arduino UNO board.

2 . Now make a python file named “dataLogger.py”

3. Now for plotting the graph using gnuplot we have to first install gnuplot using terminal by following command :

Sudo apt-get installgnuplot

Now after installing gnuplot we have to again make one new file named “plotData.plt”

Now after doing all this we have to do following steps :

1 .Go to that particular file location where you have saved dataLogger.py &plotData.plt files

2 .Now type following command

Sudo python dataLogger.py

This code will continuously shows the temperature in terminal and at the same time that data will stored into the file named “tempLog.dat”. The temperature is stored with the rate of one entry per second and listed all the sensed temperature into the “tempLog” until we give keyboard interrupt.

Screenshot of temperature sensing in terminal

Screenshotof tempLog.dat file

3. Now type following command

SudognuplotplotData.plt

This code will generate the plot of collected temperature data which are stored into the “tempLog.dat” file and generates the PNG file named “data.png” and in this file the image of graph plotted is shown.

Plot generated by gnuplot

4. For plotting in real time , install “matplotlib” in raspbian through terminal and then make one python code for it named “real_time_plot.py”

Then type following command for start reading and plotting in real time.

Sudo python real_time_plot.py

This command will show real time continuous plot of temperature. At the same time the alarm LED will start glowing and fan will start automatically when the temperature will in the range of 40 to 50 degree. For any other temperature that fan will turned off and normal LED will glow.