• Low price
• Expansion connector for interface RaspBerry Pi to external world (GPIO, SPI, I2C and UART).
• All the standard peripherals are present (Ethernet, USB, SD card, TFT, etc).
• The only negative is that the documentation is abundant, but is scattered on different websites. This cause a difficulty to find the right information.

INTRODUCTION

If you read here means that you are holding a Raspberry Pi board and maybe you are eager to use it, but if you didn't documented yourself before, now you must buy also:

• SD Card da 4/8Gbyte
  I recommend you choose a fast SD because the performance of your Raspberry Pi will be affected by the speed of the SD you choose.
• USB keyboard
  
• USB mouse
  
• RJ45 cable for connect your RaspBerry Pi to the Modem ADSL e/o Router
• Monitor or TV with HDMI interface
  
• 5V USB power supply - 1A to 1,5A (remember that we will use also expansion board and USB WiFi)
• USB cable - USB-A to Micro-USB
• Optionally an USB-WiFi adapter
  

Now you must connect the peripherals shown below in red.

Operating System (OS)

The Raspberry Pi is designed to work with Linux but we know that there are different versions, on this manual we uase the Raspbian "wheezy" (derived from Debian).
Raspbian is the recommended Linux version for RaspBerry Pi.

Download and install the Raspbian on SD card.
On Internet there are a lot of explanation, I highlight below some links.

For who use a PC with Windows see below:
http://www.raspberrypi.org/wp-content/uploads/2012/12/Raspberry_Pi_-_Guida_veloce.pdf (In Italian language)
http://www.raspberrypi.org/wp-content/uploads/2012/04/quick-start-guide-v2_1.pdf (In English language)

For who use a LINUX or MAC see below:
http://www.raspberrypi.org/downloads

Here is my step by step for download and install Raspbian on SD card of 8GB.

• Format your SD card as FAT32
  For who use LINUX I suggest to use gparted.
  For who use Windows I suggest to use Win32DiskImager.

• Download RaspBian from here:
  http://www.raspberrypi.org/downloads
  in the Internet page go down untill you find the RaspBian image (see below).
  

• After the download, unzip the file and you get a file with extension .img
• For install this file on the SD card from Linux I suggest to use the ImageWriter, if on your Linux distribution is not istalled use your Software Center for install it.

-

NOTE:

For Turn Off your RaspBerry Pi use the command:

sudo shutdown -h now

or

sudo halt

ATTENTION:

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LEDs on RaspBerry Pi

  On the RaspBerry Pi there are 5 leds that are:

Color          Name
ORANGE         100
GREEN          LINK
GREEN          FDX
RED            PWR
GREEN          ACT

During normal run the led 100, LINK, FDX and PWR are ON, and sometime flashing the led ACT (ACT when is on, highlight the access to the SD card).
When the RaspBerry Pi is stopped, only the PWR is ON, remember that for turn off is necessary do the command below.

sudo shutdown -h now

When is ON only the led PWR (all other leds are OFF), is possible remove the power to RaspBerry Pi.

If you use only the USB WiFi for connect the RaspBerry Pi to the Access Point, you see ON only the led PWR and sometime flashing the led ACT (ACT when is on, highlight the access to the SD card).

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Raspi Config

This is a configuration utility tha is run automaticaly at first power on of your RaspBerry Pi.
This utility permit to configure your RaspBerry Pi.

For execute the configuration utility using this command (from terminal/shell):

sudo raspi-config

For surfing inside the menù use the arrow keys and the tab key.
The fundamental things that you must do are:

1. configure the keyboard

2. do the update of the SW

3. espand the filesystem, this is for use all the space that there are on SD card. 

4. Configure your local time, during this configuration you must chose a server where your RaspBerry Pi find the references for your local time.
   Remember that on the RaspBerry Pi is not present a RTC, the only way to mantain your RaspBerry time after a power on is a Internet connection.
   

5. Enable the ssh, is wery important because by this way we have the possibility to control from a remote PC our RaspBerry Pi.
   For do this chose:
       Advanced Options
       SSH

6. If you enable boot_behavior after the power on is started the graphics interface of Raspbian (LXDE).
   I suggest to not enable this option, in any case is possible start the LXDE using the command:
   startx
   from a terminal.

NOTE:
-
The default user is:

raspberry login: pi
password: raspberry

I suggest you to change the password from the menù: change_pass

-

At this point your RaspBerry Pi is configured and running.

Our key point is to use the RaspBerry Pi without display, keyboard and mouse, for this reason is important to know the IP address of our RaspBerry Pi (related to the lan where RPi is connected, normaly our network at home).

For discovery the IP address of your RaspBerry Pi there are different possibility, one is to use the command ifconfig from a terminal of our RaspBerry Pi:

ifconfig

lo Link encap:Loopback locale
indirizzo inet:127.0.0.1 Maschera:255.0.0.0
indirizzo inet6: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:47074 errors:0 dropped:0 overruns:0 frame:0
TX packets:47074 errors:0 dropped:0 overruns:0 carrier:0
collisioni:0 txqueuelen:0

Another way to find the IP is: nmap

UP

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Discovery the IP of our RaspBerry Pi from remote PC

Suppose that your RaspBerry Pi is connected to a LAN, for discovery the IP address of it, follow the explanations below.

From a remote PC with LINUX (connected to the same LAN) open a terminal and use the command:

nmap -sP 192.168.1.1-255

obviously change the: 192.168.1.1
and use the IP address for your Access Point or Router.

You receive an answer from the nmap command, similar to the image below.

My RaspBerry Pi name is: rpi1.station and the IP is: 192.168.1.5

ATTENTION: if nmap is not present on your Linux distribution, install it using the following command:
sudo apt-get install nmap
or
sudo su
install nmap

UP

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If you use a remote PC with Windows, for discovery the IP address of your RaspBerry Pi, I suggest to use: Angry IP Scanner that is free.

Below a immage of a scan of a LAN.

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Control RaspBerry Pi from remote PC

Normally, the Raspberry Pi is used in control applications, and is mounted in cabinets or in places difficult to access, which is why it is essential to remote the control of our Raspberry Pi by using a remote PC.
To do what is written above, there are several possibilities that are:

• Remote control by Ethernet

• Remote control by RS232

Leaving aside the possibility of using the RS232 due to the fact that on modern PCs no longer exists, we will focus on remote control via Ethernet.

To control via the Internet Raspberry Pi is essential to have enabled in the configuration, the SSH server. If you have not already done so read here.

In practice, the control is carried out as shown in the figure below.

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How to use a remote terminal using Putty o Kitty (PC with WINDOWS)

The first thing to do is to install: PUTTY o KITTY
(install it on PC with LINUX but also on PC with Windows)
By using Putty or Kitty we have the possibility to control our RaspBerry Pi using remote PC and a terminal (shell).

• Enter the IP address of the Raspberry Pi, on how to locate the IP address see here.

• Save the configuration.

For your convenience I have put below the main windows PUTTY you will need to fill out; see the red rectangles.

ATTENTION:

ATTENTION:

LINK

• http://www.vincenzov.net/taccuino/RaspberryPI/ssh.htm

• http://www.engeene.it/controllare-da-remoto-una-raspberry-pi/

• http://raspberrypi4dummies.wordpress.com/2013/03/17/connect-to-the-raspberry-pi-via-ssh-putty/

• http://cplus.about.com/od/raspberrypi/a/How-Do-I-Setup-Ssh-On-Raspberry-Pi.htm
  

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How to use a remote terminal (PC with LINUX)

You must know the IP address of your IP del RaspBerry Pi, (see here or use the command nmap see here.

To log on to your Raspberry Pi, you have two possibilities: via terminal using the command ssh or use PUTTY.

• SSH
  From a remote PC use the command:
  ssh IndirizzoIPdelRaspBerry -l pi
  remember that pi is default login or RaspBerry Pi, if you have changed it you must change also here.
  

  EXAMPE:
  ssh 192.167.111.31 -l pi
  obviously 192.167.11.31 is the IP of my RaspBerry Pi, change this IP with your IP
  
  ATTENTION:
  On my PC where I have Xubuntu, occasionally, by using the ssh command I happen to not be able to login to the restart of the PC, see here.
  
  

• PUTTY
  This is the mode that I recommend because PUTTY is available for both LINUX and Windows and works perfectly.
  
  To install it, go to the Software Center and download it to your PC.
  
  

UP

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The graphics from remote

On our Raspberry Pi there is Linux version: Raspbian, it is also available a graphical interface which is called X.
Directly from a shell of RaspBian we can launch the GUI by running the command:

startx

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Graphics for remote PC with LINUX

By using a remote PC and Linux you have different possibility, here we show two possibility, see below.

1) VNC server

On RaspBerry Pi

Install the VNC server on your RaspBerry Pi, for do this, after you have connected your remote PC to your RaspBerry, use the command:

	sudo apt-get install tightvncserver tightvnc-java

Now start the server:

	vncserver :1 -geometry 1200x700 -depth 24

During the installation the vncserver ask you to insert a password, chose one easy to remember.
Obviously replaced 1200x700 with resolution of your remote PC.

To start the vncserver automatically at power on of your Raspberry Pi do this:

NOTE:

• Give a lower resolution than that of your remote PC so as to have a window in which there are not the vertical and horizontal scrollbars.
• After a power on if your RaspBerry Pi do not accept by remote PC a connection by vncviewer do this:
  From a remote PC connected in terminal mode to your RaspBerry Pi do the command:
  vncserver :1 -geometry 1200x700 -depth 24



On remote PC (that use Linux)

On your remote PC now is necessary install vncviewer, for do this open a terminal and follow the instructions below.

sudo apt-get install vncviewer

For run vncviewer use the command:

vncviewer 192.168.1.3:1

Obviously, replace 192.168.1.3 with the IP address of your Raspberry Pi, see here.

2) ssh

ssh -X 192.167.111.31

Obviously, replace 192.168.1.3 with the IP address of your Raspberry Pi, see here.

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Graphics for remote PC with WINDOWS

If on your remote PC you use Windows I suggest you to use this X emulator that is free.

Another possibility is to use Xming that is X server and is open source.

UP

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Manage remote files from your PC with LINUX to the RaspBerry Pi

From a terminal/shell from the remote PC you can use the commands below.
Please read this note.

Copying files from: PC to Raspberry Pi

scp LocalFile RemotePCName@IPaddress:DestinationFile

example:

scp geo.pdf pi@192.168.1.3:~/geo.pdf

Copying file from: RaspBerry Pi to PC

scp pi@192.168.1.3:~/PY/P1.py P1.py

We taken the file P1.py from the directory of the Raspberry Pi: /home/pi/PY
and copied it on your PC in the directory where you are.

Copying directory from: remote PC to RaspBerry Pi

On RaspBerry Pi is necessary create the destination directory, for example:

cd /var/www

do the new directory:

sudo mkdir phpMyAdmin-4.1.2-all-languages

enable all privileges:

sudo chmod 777 phpMyAdmin-4.1.2-all-languages

at this point from the remote PC use the command below:

scp -rpC phpMyAdmin-4.1.2-all-languages pi@192.168.1.3:/var/www/

NOTE:

pi@192.168.1.3 - change this with your address of RaspBerry Pi
phpMyAdmin-4.1.2-all-languages this is the directory that is on remote PC and that we want to copy on the RaspBerry Pi.
/var/www/ is the directory on the RaspBerry Pi where we copy the files.

UP

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Manage remote files from PC with WINDOWS to the RaspBerry Pi Windows

For who use on remote PC Windows I suggest to use the WinSCP see the link below.

http://winscp.net/eng/download.php

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How to connect a USB WiFi (SITECOM N300)

Log on to our Raspberry Pi using the RJ45 cable is definitely very reliable but also inconvenient, it is certainly more convenient to use a connection via WiFi key.

To do this you can use a lot of WiFi keys, here is a list of the keys compatible with our Raspberry Pi.

enrico@enrico-MM061:~$ nmap -sP 192.168.1.1-255
Starting Nmap 5.21 ( http://nmap.org ) at 2013-12-28 01:00 CET
Nmap scan report for vodafone.station (192.168.1.1)
Host is up (0.0011s latency).
Nmap scan report for android-9e52b9407176d692.station (192.168.1.2)
Host is up (0.051s latency).
Nmap scan report for android-b1a38c6c82d7340e.station (192.168.1.3)
Host is up (0.032s latency).
Nmap scan report for fritz.repeater.station (192.168.1.4)
Host is up (0.062s latency).
Nmap scan report for enrico-MM061.station (192.168.1.6)
Host is up (0.00038s latency).
Nmap scan report for enricohp.station (192.168.1.7)
Host is up (0.034s latency).
Nmap scan report for rpi1.station (192.168.1.9)
Host is up (0.0099s latency).
Nmap scan report for DCS-930L-DestroCortile.station (192.168.1.10)
Host is up (0.00080s latency).
Nmap scan report for DCS-930L-Pedonale.station (192.168.1.11)
Host is up (0.00075s latency).
Nmap scan report for DCS-930L-SinistroCortile.station (192.168.1.12)
Host is up (0.00075s latency).
Nmap scan report for rpi1.station (192.168.1.14)
Host is up (0.034s latency).
Nmap done: 255 IP addresses (11 hosts up) scanned in 3.40 seconds
enrico@enrico-MM061:~$

enrico@enrico-MM061:~$ nmap -sP 192.168.1.1-255
Starting Nmap 5.21 ( http://nmap.org ) at 2013-12-28 01:22 CET
Nmap scan report for vodafone.station (192.168.1.1)
Host is up (0.0018s latency).
Nmap scan report for android-b1a38c6c82d7340e.station (192.168.1.3)
Host is up (0.012s latency).
Nmap scan report for fritz.repeater.station (192.168.1.4)
Host is up (0.0057s latency).
Nmap scan report for enrico-MM061.station (192.168.1.6)
Host is up (0.00028s latency).
Nmap scan report for enricohp.station (192.168.1.7)
Host is up (0.0030s latency).
Nmap scan report for DCS-930L-DestroCortile.station (192.168.1.10)
Host is up (0.0012s latency).
Nmap scan report for DCS-930L-Pedonale.station (192.168.1.11)
Host is up (0.0011s latency).
Nmap scan report for DCS-930L-SinistroCortile.station (192.168.1.12)
Host is up (0.0012s latency).
Nmap scan report for rpi1.station (192.168.1.14)
Host is up (0.0057s latency).
Nmap done: 255 IP addresses (9 hosts up) scanned in 3.44 seconds
enrico@enrico-MM061:~$

I need to schedule, every minute, the execution of the WiFiTest.sh, for do so I used the commands shown below.

sudo crontab -e
add to the end of file the line below:
*/1 * * * * sudo /home/pi/Utility/WiFi/WiFiTest.sh >/tmp/tmp.txt
Save the file using CTRL+X and next Y(es).

For checking if really every minute cron is executed, use two command below at the distance of one minute.
    ps -ef | grep cron
See the two reds box below.



To see the result of the operation see the file /tmp/tmp.txt (see below, use the command: cat /tmp/tmp.txt).

Test the WiFi connection
*** The WiFi connection is OK ***
 
Please wait 5sec, a second test of WiFi is being processed
*** The WiFi connection is OK ***
END Test of the WiFi connection

UP

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Control the mcu temperature on your RaspBerry Pi from remote terminal

To know the temperature of cpu use the command below from terminal/shell.

vcgencmd measure_temp

UP

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Control the RaspBerry Pi from Android

https://play.google.com/store/apps

and try to type: Raspberry Pi
you will see many apps available for the most varied fields of use.

Some applications, the most advanced, those that directly control the GPIO, require the installation of a dedicated software on the Raspberry Pi, but if you just want to know if your Raspberry Pi is working then I suggest: RasPi Check

https://play.google.com/store/apps/details?id=de.eidottermihi.rpicheck

UP

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How to install a server Apache2, PHP5 and the relative libraries

For install Apache2 use the command below:

sudo apt-get install apache2

For install PHP5 use the command below:

sudo apt-get install php5

For install the library "bridge" from Apache2 and PHP5 use the command below:

sudo apt-get install libapache2-mod-php5

Now in order to use Apache2 like a Web Server visible from an remote computer (compared to Raspberry Pi) do the modification explained below.

Go to the directory below: 

cd /etc/apache2/sites-enabled/

Edit the contents of the file 000-default use nano as editor, enter the command:

sudo nano 000-default

change None with All, see the red box below.

Save the file (Ctrl X).

Now restart Apache2, to do this use the command:

sudo service apache2 restart

To check if everything went well we open our browser (always from the remote PC) and write the IP address of our RaspBerry Pi.
If you've done everything correctly, there must appear a page similar to this one.

UP

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How to install the data base MySQL, plus the package for PHP5, etc

For install MySQL on RaspBerry Pi from a remote PC connected to terminal/shell do the command:

sudo apt-get install mysql-server mysql-client

During the installation the SW is request a password for MySQL root user, see below.
Remember that the MySQL root user name is root.

Install the libraries for PHP5, use the command below.

sudo apt-get install php5-mysql

Install the libraries for Python, use the command below.

sudo apt-get install python-mysqldb

Clean the system from the files not used, use the command below.

sudo apt-get autoremove

Restart the MySQL server, use the command below.

sudo service mysql restart

Fot check if the installation is OK, use the command below.

sudo service mysql status

If you've done everything correctly, there must appear a page similar to this one.

UP

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Graphics interface for MySQL

To administer a MySQL by a GUI suggest you also install the phpMyAdmin, follow the instructions below.

From remote PC open your browser and go to this address:

http://www.phpmyadmin.net/home_page/index.php

Next press the download key.

At the end of the download, unzip it and you must see something like below.

Copy the directory: phpMyAdmin-4.1.2-all-languages
on RaspBerry Pi in the directory: /var/www
for do this follow the explanation below.

From remote PC connect to the Raspberry Pi and go to the directory:

cd /var/www (directory on the RaspBerry Pi)

Create the destination directory:

sudo mkdir phpMyAdmin-4.1.2-all-languages

Give all permissions to the newly created directory:

sudo chmod 777 phpMyAdmin-4.1.2-all-languages

From remote PC go where is the directory to copy. Copy from remote PC to RaspBerry Pi. Use the command below.

scp -rpC phpMyAdmin-4.1.2-all-languages pi@192.168.1.3:/var/www/

For more info on scp see here.

Rename the directory in phpmyadmin, use the command below.

sudo su

mv phpMyAdmin-4.1.2-all-languages phpmyadmin

To check if you did everything correctly on the remote PC, open your browser and give the address of your Raspberry Pi e /phpmyadmin, see below.

192.168.1.3/phpmyadmin/

You must see something like below

Now insert the User Name (of MySQL) for root, normally is root and next insert the password that you choose when you installed MySQL, see here.

After a few seconds you have to get the image below.

Well, everything works perfectly.
To exit this interface click on the icon highlighted below.

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PYTHON

Why using Python ? Here my answers:

• Python is relatively simply to learn

• Python is available on different Operating System

• There are a loot of libraries available for industrial control system

The alternative that I could imagine is C but it is certainly more difficult to learn.
Python is an interpreted language.

UP

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Versions of Python

Today are available two version and are:
Python 2.x.x
Python 3.x.x
The differences from this two version are in the links below.

• http://www.cs.carleton.edu/faculty/jgoldfea/cs201/spring11/Python2vs3.pdf
• http://okpanico.wordpress.com/2011/09/12/python-differenze-fra-le-versioni-2-e-3/

The standard librariers of Python are here:

• http://docs.python.org/2/library/

• http://docs.python.org/3/library/

In this manual I used the Python v.2.7.3.

For check if Python is present on your RaspByan use the command below:

python -V

The answer must be similar to this (see below):

From a terminal if you write: Python
you enter in the command interpreter and you have the possibility to test immediately the syntax of Python.

For exit from the interpeter type: exit()

Very useful is the utility pip that is a tool for manage the Python libreries.
For instal pip use the command below:

sudo apt-get install python-pip

Basically the structure of the programs is accomplished simply identation (aligning with the right TAB) the instructions you write.
You no longer need to declare variables before using them.
The data types are automatically assigned according to the contents used during the assignments.
Python has the following keywords or reserved words; they cannot be used as identifiers

    and
    as
    assert
    break
    class
    continue
    def
    del
    elif
    else
    except
    exec (changed to a built-in function in 3.x)
    False (added in 3.x)
    finally
    for
    from
    global
    if
    import
    in
    is
    lambda
    None (added in 3.x)
    nonlocal (added in 3.x)
    not
    or
    pass
    print (changed to a built-in function in 3.x)
    raise
    return
    True (added in 3.x)
    try
    while
    with
    yield

Below some link regarding Python.
http://www.emcu.it/Python/Python.html
http://www.python.org/
http://www.tutorialspoint.com/python/index.htm
http://docs.python.org/2/tutorial/datastructures.html
http://www.python.it/doc/
http://docs.python.it/html/tut/tut.html
http://www.sthurlow.com/python/
http://www.learnpython.org/
https://www.youtube.com/watch?v=_iX9CSX09Z8

For execute a Python program you must use the syntax below.

python file-name

NOTA:
In a real program, that is a file, the first line must contain the pointer to the command interpreter of Python.
On Raspberry Pi that use RaspBian must be:

#!/user/bin/python

Our first Python program.
First I suggest to create a directory for our examples, I suggest the name PY.
Next, in the directory PY we create P1.py ,  follow the steps below.

cd /home/pi
mkdir PY
cd PY
nano P1.py

Write in P1.py the lines below.

#!/user/bin/python
print "Ciao da RaspBerry Pi"

Save the file (ctrl + X) and next use the command:

python P1.py

if you did everything correctly you must see something like this:

-

Of course there are Integrated Development Environments (IDE) that make life easier for programmers.
Look for example here:

https://wiki.python.org/moin/IntegratedDevelopmentEnvironments

UP

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Library for manage the GPIO

To manage the various devices of our Raspberry Pi exist numerous libraries developed for Python, the first library that we download is for management the GPIO.
To do this, type:

sudo apt-get install python-rpi.gpio

The DOC is here:

• https://pypi.python.org/pypi/RPi.GPIO
• http://code.google.com/p/raspberry-gpio-python/wiki/BasicUsage

UP

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General purpose libraries

For the Python language were created several libraries ready for the most diverse areas of application which you can find here:

• http://docs.python.org/2/library/

• http://docs.python.org/3/library/

• https://pypi.python.org/pypi?:action=browse&c=533&show=all
  
  

• WiFi library:
  
  • https://pypi.python.org/pypi/python-wifi
    
    
  • https://wifi.readthedocs.org/en/latest/
    For install it use the command: sudo pip install wifi
  
  
• Twitter library: https://github.com/ryanmcgrath/twython
  For install it use the command: sudo pip install twython
  
  
• For drive the Serial COM I suggest:
  
  pySeria
  http://pyserial.sourceforge.net/index.html

UP

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GPIO in OutPut mode

-

We modify the program P1.py (nano P1.py) as shown below to make flashing the output GPIO4.

#!/user/bin/python

import time

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.OUT)

print "Ciao da RaspBerry Pi"
print "Gestione GPIO4 che lampeggia con frequenza di 2sec"
print "Per fermare questo programma premere ctrl + c"

while True:
    GPIO.output(4, True)
    time.sleep(2)
    GPIO.output(4, False)
    time.sleep(2)

Save it and run it as superuser, see below:

sudo su

python P1.py

If you connect a multimeter, set to measure a DC voltage, to the GPIO connector between the pin7 (positive, GPIO4) and pin6 (negative GND) you will notice that the voltage changes from 0 to 3.3 V (approximately) in intervals 2sec (2sec at 0V and 2sec at 3.3V).

If you use the expansion board FT1060M , you see flashing the led named LD5.

Let's go into the details of the program just released.

#!/user/bin/python
pointer to the command interpreter Python.

import time
inclusion of the TIME library, we will use the method of sleep so timing the LED will flash.

import RPi.GPIO as GPIO
the above line import library Rpi.GPIO and create a reference name that is GPIO. We will use GPIO in the continuation of the program.

GPIO.setmode(GPIO.BCM)
with this line we set the pin numbering of GPIO.
For the numbering there are two ways which are:

• Riferimento alla numerazione dei pin del connettore GPIO del RaspBerry Pi - GPIO.setmode(GPIO.BOARD)

• Reference for BCM that is more low-level and refers to the Broadcom SOC, it is obvious that serve a map to figure out which of the GPIO pin is referenced. This method is not convenient to use but it has been reported here for your information.
  

If we had used the numbering: GPIO.setmode(GPIO.BOARD)
we wrote: GPIO.setup(7, GPIO.OUT) to access to the GPIO4

GPIO.output(4, True)
set pin4 at 1 "True"

GPIO.output(4, False)
set pin4 at 0 "False"

while True:
with this line we create an infinite loop in the code.
For exit from this program is necessary press: ctrl + c

P2.py – Flashing the GPIO4

Below is a program similar to the above but using a different enumeration of the GPIO:
GPIO.setmode(GPIO.BOARD)
and also use a call to a function - Blink

#!/user/bin/python

import RPi.GPIO as GPIO     ## Import GPIO library
import time                 ## Import 'time' library. Allows us to use 'sleep'
GPIO.setmode(GPIO.BOARD)    ## Use board pin numbering
GPIO.setup(7, GPIO.OUT)     ## Setup GPIO Pin 7 to OUT
##Define a function named Blink()
def Blink(numTimes,speed):
    for i in range(0,numTimes):     ## Run loop numTimes
        GPIO.output(7,True)         ## Switch on pin 7
        time.sleep(speed)           ## Wait
        GPIO.output(7,False)        ## Switch off pin 7
        time.sleep(speed)           ## Wait
        print "Done ",              ## When loop is complete, print "Done"
        print i

## Ask user for total number of blinks and length of each blink
iterations = raw_input("Enter total number of times to blink: ")
speed = raw_input("Enter length of each blink(seconds): ")

## Start Blink() function. Convert user input from strings to numeric data types and pass to Blink() as parameters
Blink(int(iterations),float(speed))

GPIO.cleanup() # Released the resources that we are used - GPIO

To learn more about the functions looks at the links shown below.

• http://www.python.it/doc/Howtothink/Howtothink-html-it/chap03.htm#6
• http://www.tutorialspoint.com/python/python_functions.htm

To download these example go here.

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GPIO in InPut mode

To use the GPIO in inputs as there are several possibilities but it is worth dwelling on the fact that here we are using a Linux system, so we need to use some resource of RaspBian kernel that alerts us when change the state of a GPIO.
This because the GPIO does not have an input buffer and there is the real possibility to lose the change of the state of some InPut.
To solve this problem the solution is use the events that allows you to declare and register an event source and then use a polling by delegating the manage of polling to the kernel.

Practically every resource can be used as a source of an event, you can use a GPIO pin, a communication socket, a pipe, etc.

Basically need:

• register the file descriptor that represents the source of the event (register method)
  

• activate the listening of the kernel by method epoll

There is a further problem is that the bounce that occurs when you press a button that generates a series of spurious transactions that can last from 5 to 30ms (see below).

The filtering of input on our Raspberry Pi must be resolved via HW using the filters Pi-Greek coupled with the Schmitt trigger or better yet use a small MCU that takes care of filter buttons and then tell us the value read (see here).

All this, however, goes beyond this manual, here we will use a coarser solution that is based on creating a filter 1sec for not listening the button after it has detected the change of state.

Below is the list of basic instructions needed to create the polling process described above.

1) import select
…
2) pin_base = '/sys/class/gpio/gpio27/'
…
3) # Creazione file descrittori per GPIO27
pin_base = '/sys/class/gpio/gpio27/'
os.system("echo 27 > /sys/class/gpio/export")

3b) # Impostazione GPIO17 come ingresso
os.system("echo 'in' > /sys/class/gpio/gpio27/direction")

3c) # Impostazione innesco evento su fronte di discesa
os.system("echo 'falling' > /sys/class/gpio/gpio27/edge")

4) f = open(pin_base + 'value', 'r')

5) po = select.epoll()

6) po.register(f, select.POLLPRI)
…
7) events = po.poll(60000)

1. import of select library
   

2. configure the file descriptor for GPIO27. The file is stored in: /sys/class/gpio/

3. from 3 to 3c, we create the descriptors for InPut pin
   

4. open in read mode the descriptor file of GPIO27

5. we create the instance epoll using object select

6. record, using the register method, the source of the event, ie, the file descriptor GPIO27

7. This line initializes the event request and waits for the occurrence of the event, pressing the button.
   60000 indicates that if no event is not trapped in an interval of 60sec, is still triggered an event that can be intercepted by the program and which serves to highlight that the mechanism is in operation.

In the select library there are several ways to management event (see picture below).

For more info see here.

To make the tests will use a button connected to GPIO27 (pin 13) of the connector GPIO our Raspberry Pi, see diagram below (for the resistance goes well on any value between 1 and 10K).

It is also possible use the FT1060M expansion card and we use P2.

ATTENTION:
The resistance on the one hand is connected to GPIO27 (pin 13) and the other side must be connected to 3.3V GPIO pin 1 on the connector.
Pay particular attention to this connection, the GPIO withstand maximum voltages of 3.3 V.

The program that we will write will be launched from super user (sudo su) because we need to access to protected directories on the Raspberry Pi.

Below is the syntax of GPIOInt.py

To download these example go here.

On complex systems based on Operatig System (SO), like Linux that is used on our RaspBerry Pi, is easy that two or more process try to use simultaneously the same HW resource.
In the SO are implemented a mechanism for avoid the multiple access to the same HW at the same time.

The same thing can happen to us if we develop complex programs on the Raspberry Pi, especially if we divide our programs into small programs, each of which deals with one thing and then a program that shows the final results of the various calculations.

Suppose we want to implement an application that:

1. Read the INGRESSI of contacts or buttons (to do this we will use the kernel - events and polling)
   

2. Drive the USCITE for example LED e/o Relè
3. Read the NTC interfaced via I2C (remember that first is necessary enable the I2C in the kernel and then you can use)
   
4. Use a DAC always interfaced via I2C
5. Display on a page accessible via the browser (we used Apache)  the state of what was done above

To develop this application we use minimal programs that implement each a single part (1, 2, 3, 4 and 5).
This structure is very modular, so then it becomes easier to manage (update) the individual modules but we have a competition problem because we have two programs that sooner or later they will try to simultaneously use the I2C peripheral.
Comes the need to save somewhere that is done by the programs 1, 2, 3 and 4 and give the possibility to program 5 to displays the results.

Solutions to this problem are different, we decided to use a particular database in MySQL that will help us to solve the problem of competition lining up processes that try to access the same database.
In practice, with this mechanism we use the database and before accessing the I2C peripherals, we go to read their status in the database and if it is busy (busy data base) will wait until that is released.

We will use the same database to track the status of the inputs, the outputs, the value of the NTC and the value that has been set to the DAC.
Then we will use an Apache server to publish a HTML / PHP that summarizes the state of the inputs the value of the NTC (temperature in ° C) and the DAC.

Soon you will find a complete example in this section.

-

How to configure the I2C bus

In the kernel of RaspBian the I2C bus is disabled (it is in the blacklisted) because this bus uses GPIO2 (pin3) and GPIO3 (pin 5) and we prefer to give priority to the GPIO.
To enable the I2C bus, follow the procedure listed below.

sudo nano /etc/modprobe.d/raspi-blacklist.conf

With the nano editor, put line of the I2C under comment, see below red rectangle.

Save the changes (CTRL + X and then Y), turn off and on the Raspberry Pi for changes to take effect.

Now we need that the new module is loaded at boot Raspberry Pi, we want it to become an integral part of the kernel RaspBian.

To do this, enter the command:

sudo nano /etc/modules

at the bottom of the file and add the line:

i2c-dev

Save the changes (CTRL + X and then Y).
To check if the module has been loaded, use the command:

lsmod

you must see a response similar to this below, see red rectangle.

Now we should also load the i2c-tools utility that provides functions that can be used directly by the shell.
To do this, follow the instructions below.

We install the package.

sudo apt-get install i2c-tools

we add pi user to our group I2C

sudo adduser pi i2c

Turn off and on the Raspberry Pi for changes to take effect.

For some applications in Python, like the card FT1060M, we would use a I2C library and there are many available, we have chosen to use the library SMBUS.
To install this library from the remote PC connected to the Raspberry Pi enter the command:

sudo apt-get install python-smbus

To use this library you should be careful in which revision of Raspberry Pi is being used, in the example program of Marco Magagnin, TempLux.py there is shown below that the definition should be changed as shown.

bus = SMBus(1) – for RPi rev.2
bus = SMBus(0) – for RPi rev.1

-

How many RaspBerry Pi are available today ?

Up to now there are two version that are: Model A e Model B.

The Model A do not have the Ethernet and the RAM is 256KB.
The Model B has the Ethernet, the version 1 has 256KRAM the version 2 has 512KRAM.

Between the Model B version 1 and version 2 there are also a differences on the GPIO connector that are show below.

Modello B versione 1:      Modello B versione 2:
GPIO pin 3  is GPIO0         GPIO pin 3  is GPIO2
GPIO pin 5  is GPIO1         GPIO pin 5  is GPIO3
GPIO pin.13 is GPIO21        GPIO pin.13 is GPIO27

To know the version of your Raspberry Pi use the command shell and type the command show below:

cat /proc/cpuinfo

you should see a response similar to this below.

A detailed description of the connectors on the Raspberry Pi, even including some of the undocumented are here:
http://elinux.org/RPi_Low-level_peripherals#GPIO_hardware_hacking

Here you will find the mapping of GPIO in the various versions of the Raspberry Pi.
http://elinux.org/RPi_BCM2835_GPIOs
http://www.panu.it/raspberry/
http://elinux.org/RPi_HardwareHistory#Board_Revision_History
http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/gpio-pin-electrical-specifications#fn__3

Below is the layout of the I/O GPIO connector of the Model B version 2.

-

NTC Thermistors and relevant formulas for their linearization

The thermistors NTC (Negative Temperature Coefficient) are normally used for measure the temperature.
http://it.wikipedia.org/wiki/Termistore
http://en.wikipedia.org/wiki/Thermistor

These components have the characteristic to change their resistive value as the temperature varies, in particular its resistance decreases with increasing temperature.
The variation of their resistive value does not follow a linear temperature variation and for this reason is necessary linearize it.
To do this you can use mathematical formulas, see below, or on small mcu 8bit you prefer to use of lookup tables that require less computational resources.
http://it.wikipedia.org/wiki/Look-Up_Table
http://en.wikipedia.org/wiki/Look-up_table

Steinhart-Hart equations

This is one of the more precise equations that have a resolution of 0.002 ° C, third order approximation.
http://it.wikipedia.org/wiki/Equazione_di_Steinhart-Hart
http://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
Steinhart-Hart Thermistor Calculator
http://it.wikipedia.org/wiki/Termistore
http://en.wikipedia.org/wiki/Thermistor

The formula is:

T temperature in kelvin
R resistance of the thermistor in ohms at the time of measurement
A, B, C and D are the coefficients of Steinhart and Hart, which vary according to the model of the thermistors and temperature range chosen. Usually these parameters are present in the datasheet thermistor you choose to use.

In case on the datasheet of our thermistor were not specified all the parameters that we need one can opt for a second method which is based on the parameter B of the thermistor and whose formula is:

R0 is the value of the thermistor to the temperature T0 that is usually given for 25°C.

B is a constant found on the datasheet of the NTC.

For our experiments we use a NTC 10K and we will use the following values:

A = 0,00335402
B = 0,000256985
C = 2,62013e-6
D = 6,38309e-8

The formula Steinhart and Hart does not take into account the effects of dissipation factor K thermistor, or dell'autoriscaldamento.
The K-factor is in turn found on the datasheet for the thermistor.
For our thermistor we have:

K = 6

The value in degrees to subtract to the result of the formula Steinhart and Hart is:

Td = V*V / K*Rth

The circuit which is typically used to detect the variations of an NTC is the following.

On this schematics must make some considerations are:

• The supply voltage (3.3 V) must be very stable to avoid introducing errors on the measurement that we will do

• The resistance R must be at least 1% accuracy or better

• The ADC must have a precise voltage reference to avoid introducing errors on the measurement that we will do

For the tests we do we will use the FT1060M card that uses the above diagram for interfacing the NTC to a MCU. MCU then talks in I2C to our Raspberry Pi.
The above mentioned mcu has a 8bit ADC that has a precision (V = 3.3 / 256)

The voltage value that we will is:

V = (ValADC * Vref) / 256

Vref is 3,3V and ValADC is the value returned by the ADC in decimal format

We measure a voltage and for get the value of the resistance, we use the formula:

Rth = (R*V) / (Vin-V)

R is15K.
Vin is 3,3V.

The Python main features are below:

R1 = 15000.0        # Resistor R
R_th0 = 10000.0     # Reference thermistor resistence at 25°C
V_IN = 3.3          # Supply voltage of divider voltage
V_REF = 3.3         # Supplay reference voltage of ADC
A = 0.00335402      # Steinhart-Hart Costant A
B = 0.000256985     # Steinhart-Hart Costant B
C = 2.62013e-6      # Steinhart-Hart Costant C
D = 6.38309e-8      # Steinhart-Hart Costant D
K = 6.0             # Fattore dissipazione K 6mV C
pB = 4100,0         # Costant of B Parametr
...
# After scanning the channel of the ADC where is connected where the NTC
# We'll do the following calculations and conversions
print "NTC - Hex ADC_0 = ",
print hex(raw_val)
# Delete the first two characters (0x) from the value read and also the final L
# Transform the result in decimal
hex_val = hex(raw_val)[2:].rstrip('L')
dec_val = int(hex_val,16)
print "NTC -Dec ADC_0 = ",
print dec_val
....
# Transformation in voltage of reading
V = (dec_val * V_REF) / 256.0 # V = (ValADC * Vref) / 256
print "Volt NTC = ",
print V
....
# Calculation of resistance
R_th = (R1 * V) / (V_IN – V) # Rth = (R*V) / (Vin-V)
print "Resistenza NTC = ",
print R_th
....
# Calculation of degrees Kelvin using the formula of the Steinhart-Har
logR = math.log(R_th / R_th0)
logR2 = logR**2
logR3 = logR**3
Stein = 1.0 / (A + B * logR + C * logR2 + D * logR3)
....
# Converting in Celsius and application of dispersion factor
Celsius = round(Stein - 273.15 - V**2 / (K * R_th),2)
# Stampa del risultato
print "Steinhart - Celsius = ",
print Celsius
....
# Calculation of degrees Kelvin with the formula of the parameter B
RRo = (R_th / 10000.0)
logRRo = math.log(RRo)
parB = 1.0 / ((1.0 / 298.15) + (logRRo / pB))
....
# Converting in Celsius and application of dispersion factor
Celsius2 = round(parB - 273.15 - V**2 / (K * R_th),2)
# Stampa del risultato
print "parametro B - Celsius = ",
print Celsius2

Below is the complete listing of the program Temp.py that measuring the NTC and tells us that the ambient temperature

#!/usr/bin/env python

# Temp.py
# By www.emcu.it
# Gen. 2014

# Import librerie
from smbus import SMBus
import math
import time

#bus = SMBus(0) # RaspberryPi modello A
bus = SMBus(1) # RaspberryPi modello B

adc_address1 = 0x4F # Imposta indirizzo 000 ADC su alcuni Rpi è 48
adc_channel1 = 0x40 #
adc_channel2 = 0x41 # Imposta indirizzi canali
adc_channel3 = 0x42 # con risoluzione di 8 bit
adc_channel4 = 0x43 #

R1 = 15000.0 # Resistenza R1
R_th0 = 10000.0 # Resistenza riferimento termistore a 25 c

V_IN = 3.3 # Tensione alimentazione partitori tensione
V_REF = 3.3 # Tensione riferimento misura ADC
A = 0.00335402 # Steinhart-Hart Costante A
B = 0.000256985 # Steinhart-Hart Costante B
C = 2.62013e-6 # Steinhart-Hart Costante C
D = 6.38309e-8 # Steinhart-Hart Costante D
pB = 4100.0 # Costante parametro B
K = 6.0 # Fattore dissipazione K 6mV C

# Inizio elaborazione

# Lettura canale 0 ADC - un byte esadecimale
# La prima istruzione imposta la richiesta di campionamento su ADC 0
# Si eseguono tre letture per evitare 0x80 all'accensione e per la precisone

# incrementale del convertire
bus.write_byte(adc_address1,adc_channel1)
raw_val = bus.read_byte(adc_address1)
raw_val = bus.read_byte(adc_address1)
raw_val = bus.read_byte(adc_address1)

print "NTC - Hex ADC_0 = ",
print hex(raw_val)

# Elimina i primi due caratteri 0x dal valore letto ed eventuale L finale
# Trasforma il risultato in decimale
hex_val = hex(raw_val)[2:].rstrip('L')
dec_val = int(hex_val,16)
print "NTC -Dec ADC_0 = ",
print dec_val

# Trasformazione in tensione del valore letto
V = (dec_val * V_REF) / 256.0
# Stampa del risultato
print "Volt NTC = ",
print V

# Calcolo della resistenza
R_th = (R1 * V) / (V_IN – V)
# Stampa del risultato
print "Resistenza NTC = ",
print R_th

# Calcolo dei gradi Kelvin con la formula di Steinhart-Hart
logR = math.log(R_th / R_th0)
logR2 = logR**2
logR3 = logR**3
Stein = 1.0 / (A + B * logR + C * logR2 + D * logR3)

# Conversione in gradi Celsius e applicazione fattore di dispersione
Celsius = round(Stein - 273.15 - V**2 / (K * R_th),2)
# Stampa del risultato
print "Steinhart - Celsius = ",
print Celsius

# Calcolo dei gradi Kelvin con la formula del parametro B
RRo = (R_th / 10000.0)
logRRo = math.log(RRo)
parB = 1.0 / ((1.0 / 298.15) + (logRRo / pB))

# Conversione in gradi Celsius e applicazione fattore di dispersione
Celsius2 = round(parB - 273.15 - V**2 / (K * R_th),2)
# Stampa del risultato
print "parametro B - Celsius = ",
print Celsius2

This program is available ready to use here.

UP

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-
How to run a LINUX process in background


Often is necessary to launch processes (programs) in the background, to do this there are several possibilities that we will see below.

Launch a process in a shell (terminal) that free us the command line

For do this is necessary append at the end of the command the character: &
Next, press twice Enter.

example:
sudo python P1.py  &

The program (it flashes an LED) is still running in the background but the command line of the terminal is available, see picture below.



However, if you close the terminal the process will be terminated.
If we want to end the process without closing the terminal must be use the kill command. to see only the active processes of PYTHON can use the command ps-ef | grep python

 
Launch a process that will free us the shell command line, and it remains active even closing the shell

To do this you need to run your program by putting the nohup before the command; append at the end of the command the character: &
Next, press twice Enter.

example:
sudo nohup python P1.py >/dev/null &

If we have written a program that at certain times to do a check and store them, and we are interested that in the rest of the hours is stationary, we can use the kernel command LINUX cron.

UP

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-

LINUX basic commands

    See this link.