Teirmilab - final building

Ok, time to close the project.
This article will be updated to track the progress.

Working on Teirmilab

Here a step-by-step guide to work on git for the TeirmiLab project.
If you are new on git and github, read this article first

TheTeirmiLab project is on bitbucket public.
If somebody wants to join it to enhance the project would be nice if contact me.
Bitbucket has limited number of collaborators unless pay.
Let start from the link for the TeirmiLab bitbucket project :
https://bitbucket.org/account/user/hanixdiy/projects/TEIR

Clone TeirmiLab

Use git to clone the TeirmiLab project (see a specific repository in the project)

That's it !

On your directory, will exist a directory called TeirmiLab, containing the code.

Or better, just download a zip file from bitbucket.

TeirmiLab - Use

This article describes how to use the  TeirmiLab.

Introduction

The TeirmiLab is a thermometer with some extra capabilities.
The design  allows for these features:

• Range -55 to 125°C (-67°F to +257°F)
• ±0.5°C Accuracy from -10°C to +85°C
• Reading in Celsius, Fahrenheit or Kelvin
• Alarm capability with visual and audio notification
• Offset capability for better tuning the sensor

It is possible to add more capabilities if needed, like data logger and remote connection capabilities.

Operations

Turning the unit On

Verify to have the temperature sensor connected to the instrument via its connector.

Then push the power button.
The light on the power button will flash, indicating that the instrument is powering on.
After approx 30 seconds, the power button light will be steady ON and the LCD display will show a welcome message for few seconds, followed by the temperature reading.
If for any reason the instrument is not starting correctly, the power will be removed automatically.
Contact the TheFwGuy for help if the problem persist.

Turning the unit Off

It is highly discouraged to remove the power supply from the instrument while is working!
Removing the power from the instrument could damage the memory card and thus having the instrument not working anymore (contact the TheFwGuy to restore functionality).
To correctly power down the instrument, push the power button.
The light on the power button will start to flash indicating that the power off procedure started.
When the power off procedure is completed and it is safe to remove the power, the light on the power button will stop to flash turning off, and the power will be removed automatically.

General settings

The instrument has two knobs just below the display.
One is used to bright or dim the display.
The other is an encoder with a switch.  Pressing the knob will change the instrument mode sequentially.
The available modes are :

1. Run  (default - the instrument starts on this mode)
2. Measurement unit setting
3. Enabling/Disabling alarm
4. Setting alarm value (only if alarm enabled)
5. Setting offset value
6. Reset the TeirmiLab
7. back to number 1

To change mode, simply press the encoder knob.

To change value, rotate the knob clockwise or counterclockwise

Note. Before to access the menu', it can require to push the encoder knob for a couple of seconds.

Measurement unit setting

The LCD  will  display on the top line "Set Unit" and on the bottom line "Celsius" or "Fahrenheit" or "Kelvin".

Turning the knob clockwise or counterclockwise will change the selection.

To exit from the Measurement unit setting mode, press the Mode button once.
The setting displayed will be used.

Enabling/Disabling alarm

The LCD will  display on the top line "Enable Alarm" and on the bottom line should be present the current status : On or Off (default Off).

Turning the knob clockwise or counterclockwise will change the selection.
If the selection is Off, pressing the Mode button will skip the Alarm Value step, going directly to the Set Offset Value selection.

If the selection is On, pressing the Mode button will go to the Setting Alarm Value selection.

Setting alarm value

The LCD will display on the top line "Set Alarm" and on the bottom line will be present the last setting for the alarm.

Turning the knob clockwise will increment the alarm value, turning it counterclockwise will decrements the alarm value.
The allowed range for the alarm is :

• Celsius, from -40 C to +120 C
• Fahrenheit from -40F to +248F
• Kelvin from 233K to 393K 

When the desired Alarm temperature is set, press the Mode button.

During the Run time, the TeirmiLab will display the current temperature in Green.

When the Alarm temperature is reached, the screen will become Red and a sound will be generated.

Press the Mode button once to reset the Alarm.

Set offset value

The LCD will display on the top line "Set Offset" and on the bottom line will be present the last setting for the offset.

Turning the knob clockwise will increment the offset value, turning it counterclockwise will decrements the offset value.

The offset is used to change the temperature reading in case the sensor measurements are not correct.

Reset the TeirmiLab

The LCD will display on the top line "Reset ?" and on the bottom line will be present the last choice as "Yes" and "No"

Turning the knob clockwise or counterclockwise will change the selection.

If the selection is "Yes", pressing the knob will cause the Reset.

The configuration file will be erased and re-created with the default values.

TeirmiLab - Raspberry Pi prototype

This article describes the building of a TeirmiLab prototype based on a Raspberry Pi B board.
The goal using a Raspberry Pi is to have a machine that can be expanded later.

Shopping list

• Raspberry Pi B or Raspberry Pi B+ or Raspberry Pi A+
• RGB 16x2 LED display
• DS1820 (specifically this one)
• MCP23017 I2C GPIO expander
• I2C RTC clock (optional)

The idea is to use a traditional LCD display instead a more sophisticate touch screen display.
Mainly the reasons :

• is not expensive
• doesn't require to develop a graphic interface for it
• allows to focus on the purpose - to show a temperature
• can be easily placed inside a protective container (no touch capabilities)

Hardware

Here a initial schematic for the TeirmiLab-Pi.

The RTC clock module is actually necessary only for the enhanced version, for the data-log feature, however it will be tested also on the base version.
The idea is to use as much as possible "ready to use" modules, like the RGB display, the GPIO I2C expander and so on, in order to use already made code (see the Software section).

The encoder will be connected directly to the Raspberry GPIO as well as the interrupt signal from the MCP23017 (optional for now), in order to be able to detect faster changes from the keyboard.
The internal pullup resistors for the encoder will be enabled.

First tests on a breadboard

The second prototype on perforated board

The second prototype on perforated board

The second prototype with the keyboard and RPOf cable connected

The keyboard is working fine, however it would be better to have an easiest way to select an alarm or set up the offset.
A new version of the hardware will include a digital encoder to be used instead the keyboard (see below).

The prototype installed on a wooden platform for a more mechanical stability.
A monochromatic LCD is used instead an RGB one

The prototype installed on a wooden platform for a more mechanical stability.
The round PCB is hosting the RPOf to be piggy-bagged on a MSP430 Launchpad

The used board for the prototype is a Raspberry Pi B, however the final installation will use a Raspberry Pi A+ because the reduced dimensions and power usage.
A new interface board is under development.

GPIO Use

Here a table for the GPIO use :

Raspberry GPIO	MCP GPIO	Direction	Description
	GPA0	Output	LCD
	GPA1	Output	LCD
	GPA2	Output	LCD
	GPA3	Output	LCD
	GPA4	Output	LCD
	GPA5	Output	LCD
	GPA6	Output	LCD
	GPA7	Output	LCD
	GPB0	Output	LCD
	GPB1
	GPB2
	GPB3
	GPB4	Input	Keyboard 1
	GPB5	Input	Keyboard 2
	GPB6	Input	Keyboard 3
	GPB7	Input	Keyboard 4
GPIO4		Input/Output	1Wire protocol
GPIO17		Input	Shutdown input
GPIO18		Output	Shutdown feedback
GPIO22		Output	Buzzer
GPIO23		Input	Encoder A
GPIO24		Input	Encoder B
GPIO25		Input	Encoder switch

Sensor

With the sensor used (DS18B20) the TeirmiLab has these basic characteristics:

• Range -55 to 125°C (-67°F to +257°F)
• ±0.5°C Accuracy from -10°C to +85°C

Keyboard

The TeirmiLab-Pi needs to have at least 3 push buttons in order to do some settings.

• a Mode button
  Allows to select different modes, like "display temperature" or "Set alarm" or "Set offset"
• two + and - buttons
  Allows to increase or decrease a value, like the alarm temperature or the offset

Encoder

Instead of the keyboard, it is more easy to use a mechanical digital encoder with an embedded pushbutton for the selection.
The pushbutton acts as Mode button and rotating the encoder cause the values to change.

The video is showing the encoder operations

Power Supply

The instrument must be powered.
An USB wall wart, with at least 1 A, will be the power source for the Teirmilab.

A main switch will be necessary in order to correctly power up and power down  the instrument (see RPOf project)

Container

All the electronic will be placed in a transparent plastic box.
This will allow to reduce the drilling to the minimum, basically for the main power switch and eventually for some push buttons if not other means are used.
The display will remain totally protected but visible behind the clear plastic.

Raspberry Pi - RPOf project

The Raspberry Pi can be used to run some kind of embedded Linux.
Like any *nix system, removing suddenly power is not a  good thing, it is very easy to corrupt  some SD card sector if the power removal happens during a writing cycle.

Raspberry Pi - connecting a traditional LCD display (Update)

Raspberry Pi is a powerful enough platform and  it is possible to use many recent touchscreen with a nice graphic on it.
However often a traditional LCD is more useful, and surely is more cheap than a touchscreen solution.

Here one way to connect a traditional LCD and use it in projects, like the TeirmiLab one.
This article describes how to connect a traditional LCD but with RGB capabilities to the Raspberry Pi B.

We need :

• Raspberry Pi B or Raspberry Pi B+
• RGB 16x2 LED display
• MCP23017 I2C GPIO expander

It is possible to hook a display without the need of the GPIO expander, however a normal LCD uses at least 6 signals. 9 if the LCD display is an RGB one like the one used for this project.
Considering that the Raspberry Pi B doesn't have many GPIO available and that usually the speed required to handle the display is not critical, using a chip like the MCP23017 make sense.
In this way it will be enough to "hook" the  chip to the I2C bus, leaving all the Raspberry Pi GPIO free for other use.

Let see a schematic.

Software

There are many ways to control the hardware.
For now I found a ready-to-use Python library published by Adafruit that is working nicely.
Again, the important thing is that control an LCD is not a critical task, so a python script is Ok.
Maybe in future I'll explore the possibility to control it directly in C.

Python 

To use our display we need to install some code in our Raspberry.
Here a quick step-by-step guide (see Adafruit tutorials for a more detailed and easy instructions) :

1. sudo apt-get update
2. sudo apt-get install build-essential python-dev python-smbus python-pip
3. sudo apt-get install i2c-tools
4. sudo pip install RPi.GPIO
5. cd ~
6. git clone https://github.com/adafruit/Adafruit_Python_CharLCD.git
7. cd Adafruit_Python_CharLCD
8. sudo python setup.py install

Before to be able to use it, we need to be sure a configuration file is correctly set-up.

Execute : sudo nano /etc/modules

and if the file exists, add these two lines in the end.

i2c-bcm2708 

i2c-dev

Save the file then open another one in edit.
Execute : sudo nano /etc/modprobe.d/raspi-blacklist.conf

In this file comment out the two lines showed below, adding # at the beginning:

#blacklist spi-bcm2708

#blacklist i2c-bcm2708

Reboot Raspberry : sudo shutdown -r now

or : sudo reboot

At this point everything should be installed in order to use the display.

First is better to run an utility to see if the I2C GPIO expander is seen correctly.

sudo i2cdetect -y 1

The command should display a table and in the table should be present a 0x20 address.

pi@raspberrypi ~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
pi@raspberrypi ~ $ 

If so, the chip is correctly seen by Raspberry.

To test if the display is working you can execute a test script :

1. cd Adafruit_Python_CharLCD/examples
2. sudo ./char_lcd_mcp.py

Some test messages should be displayed on the LCD display.

Troubleshooting

It is possible to have some problems installing the libraries.
Here a couple of tips and resolutions.

apt-get missing

If you start from a fresh installation of Raspbian, especially a lite version, before to start to follow the instructions above, be sure to execute :

• sudo apt-get update
• sudo apt-get upgrade
• sudo apt-get update

It is important because updating the first time, include more repo on apt-get.

python build fail

If during the python building of the library you have this errors :

python ./setup.py build

Downloading https://pypi.python.org/packages/source/s/setuptools/setuptools-3.5.1.zip

Extracting in /tmp/tmpw6UbTx

Traceback (most recent call last):

  File "./setup.py", line 4, in

    use_setuptools()

  File "/home/pi/Adafruit_Python_CharLCD/ez_setup.py", line 128, in use_setuptools

    return _do_download(version, download_base, to_dir, download_delay)

  File "/home/pi/Adafruit_Python_CharLCD/ez_setup.py", line 108, in _do_download

    _build_egg(egg, archive, to_dir)

  File "/home/pi/Adafruit_Python_CharLCD/ez_setup.py", line 57, in _build_egg

    with archive_context(archive_filename):

  File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__

    return self.gen.next()

  File "/home/pi/Adafruit_Python_CharLCD/ez_setup.py", line 88, in archive_context

    with get_zip_class()(filename) as archive:

  File "/usr/lib/python2.7/zipfile.py", line 770, in __init__

    self._RealGetContents()

  File "/usr/lib/python2.7/zipfile.py", line 813, in _RealGetContents

    raise BadZipfile, "File is not a zip file"

zipfile.BadZipfile: File is not a zip file

this happens because for some magic reason :) the python script screw up the download of a zipped file.

In my case the file was setuptools-3.5.1.zip.

Doing an ls -l showed up to be 122 byte big !! Definitively NOT a zip file.
The workaround was quite easy actually.

• remove the file : sudo rm setuptools-3.5.1.zip
• manually download the file :
  wget https://pypi.python.org/packages/source/s/setuptools/setuptools-3.5.1.zip 
• Re-execute the build : sudo python ./setup.py build

Examples

Be aware about the type of kit you are using.
On the examples area there are different examples depending the type of display in use.

To test the basic display, use : char_lcd_mcp.py
To test the kit with RGB display and pushbutton use : char_lcd_plate.py

TeirmiLab - prepare Raspbian

For the TeirmiLab project, one of the platform I choose to prototype it, is the Raspberry Pi B (or B+).

This is a quick step-by-step reminder about how to prepare Raspbian for the Raspberry Pi B and B+ for this project.

There are on-line hundreds of places where is described how to install a Raspbian over a Raspberry Pi.


If this quick step-by-step is not enough for you, try this.
If you think that this is too technical ... are you sure you want to play with microcontrollers ? :)

Lets start.
I used a 8 Gbyte micro SD card with a low profile adapter. In this way is easy to eventually swap to the Raspeberry Pi B+.

It is necessary, at least for the installation, to have :

• a 5 Volt 1A USB power supply
• a USB cable (microUSB) for the power supply
• an internet connection, better if wired
• a computer (needed to download the image and prepare the SD card)

Optionally if you want to enable the graphic interface or plan to use Noobs, better to have also:

• a HDMI monitor or a composite monitor (suggested an HDMI one)
• an USB keyboard
• an USB mouse

As keyboard and mouse, I used a wireless Logitech keyboard with an included touch-pad with USB dongle, in this way there is still available an USB Port.

SD card preparation  

Once all the HW components are available and connected, is possible to prepare the SD card.
Raspberry Pi does not have flash, it boots from the SD card that is used also as hard drive.
Because of that it needs to be formatted in Fat32.

Using kparted erase all the data on the SD card (new partition) and then simply format all the card in Fat32.
If you DON'T plan to use Noobs, there is no need to format the SD card.

Problems
Use a decent SD card for the job.
It should be fast and good quality/brand.
I had some SD cards not working properly because not fast enough or bad brand.
I found more reliable to use microSD cards with the adapter.

Installing distribution

There are two main choices about installing a distribution/OS on the SD card:

• installing Noobs
• installing a specific distribution

Noobs
If you choose to use Noobs, here some notes.
It is easier, shows you the latest available distributions and install automatically everything needed.
You must connect an HDMI monitor and a keyboard/mouse to the Raspberry Pi.

To install Noobs, simply download it and extract it on the SD card.
That's it. No strange formatting of the SD card, no partitions, secret code, ecc.
Just a plain copy.

Once copied, insert the card on the Raspberry Pi and turn it on.
After few seconds will appear on the HDMI screen the list of available OS to install.
If you have enough space on the SD card, it is possible to install more than one.

With 8Gbyte SD card, generally there is space for 1 or 2 OS.

The suggested distro to install is the Raspbian , accessible via the Noobs menu.

It is a Debian based distro and is probably the most used.
Once installed, a configuration menu' will allows to set up some parameters, like starting the distro in graphic mode rather than command line.
The default is command line ! So it is normal to boot in command line if no configuration modifications are made.

Raspbian
It is possible to install directly Raspbian. The main advantage is to have much more space on the SD card.
Here how to do it.
Go on the Raspberry Pi website download page , locate the Raspbian image and download it on your computer (look for Operating Systems Images - Raspbian).
Detailed explanations about how to do that are available on the Raspberry website, shortly here a quick reminder. I'm using Linux and I'm assuming you KNOW how to work on Linux.

• download the image on your PC
• extract the image from the zip file
• open a terminal
• df -h
  to see what memory devices are present
• insert the new SD card
• df -h
  identify the latest device inserted - ignore the partitions, we need to overwrite the entire card with the image
  If nothing appears, try with gparted or kparted to identify the new card
• umount /dev/sdxx
  umount the device added if for any reason it was mounted.
  In case the card has more than one partition, umount all of them.
  Eventually better reformat the card with gparted so to have a single partition but is not necessary.
• copy the entire image downloaded on the sd card with the command:
  
  dd bs=4M if=name_image_downloaded.img of=/dev/sdx
  
  where name_image_downloaded is the path/name of the downloaded Raspbian image and sdx is the name of the unmounted device (DEVICE !  NON PARTITION !)
  
  CAUTION!  Take your time and triple check ! If you use the wrong /dev you can lose your data !

At this point you have the SD card ready to be inserted in the Raspberry Pi.
Do it, be sure to have connected the board to the network, no need to have HDMI and keyboard/mouse, you can operate via ssh.

The image installed allows for the default user named 'pi' and password 'raspberry'.
Hook up  a terminal to the board, for example in ssh, is possible to login with:

- ssh pi@192.168.xxx.xxx   (address of the board - see your DHCP assignment)
- password : raspberry

Once gained access, is better to do an update with :  sudo apt-get update

After the reboot is better to configure Raspbian running the command sudo raspi-config.
At least run the option
- Expand Filesystem and the
- Advanced Options/A6 I2C in order to enable the I2C support.

No need to run other options.

The Raspberry Pi B (or B+) board is ready for the next step.

TeirmiLab - Designing a laboratory thermometer

Sometime is necessary to "reinvent the hot water".
In a  laboratory is necessary to measure the temperature of liquids and not always are easily available the last technological gadgets or practical one.

This article describes very generally some characteristics, requirements and usage of the gadget to design, a thermometer to be used in a laboratory

Important ! This project is based on specific requirements. Is not meant to be a "universal laboratory thermometer" but rather an instrument with specific characteristics needed in a specific laboratory.
The idea is that it can become a starting base for similar lab thermometers.

So here this project trying to design and build quickly a thermometer suitable to be used in a laboratory : the TeirmiLab

Lets start with the name.
The name is invented taking the first part of the Irish translation of "thermometer" (teirmiméadar) and of course "Lab" does not need of explanation.
Why Irish ? Well, I liked the sound of the name. The beauty of globalization.

The idea is to have a versatile and flexible instrument, capable to collect temperatures with probes attached to the display unit, measuring the current temperature, the minimum one, the maximum and work optionally as data logger.

The TeirmiLab can be also connected to a network (enhanced version), adding the possibility to see the current measurement in real time over a browser and adding graphic capabilities, remote setting of the unit and so on.

On the market do exists a lot of thermometers for laboratory use, but one of the goal of the project is to create an open platform and a thus customizable one, without spending up to thousand dollars.

The precision of the TeirmiLab initially is set as the sensor used, the DS1820. 

Requirements

The TeirmiLab should be able to performs these functions (the list has no particular priority)

Basic

• minimal and intuitive user interface
• read one sensor. The sensor should be detachable to be able to change it or clean it
• display the temperature away from the sensor
• display the temperature in Celsius or Farheneit or Kelvin
• Alarm
• Capability to offset the reading locally (setup)
• Capability to set the alarm locally

Enhanced

• read more than one sensor
• display locally the min and max temperature
• data logger capability
• capability to store locally temperatures for an amount of time
• setting for the measurement interval
• setting for start and stop
• capability to transfer the log to a remote computer
• remote connection capability
• setting alarms
• offsetting a probe
• download log
• reset log
• remote display capability
• (optional) print results locally
• (optional) RFID reader for identification 

Let see more in details some requirements for the basic version/

Minimal and intuitive user interface

In a world of "apps" it is easy to forget that sometime is more important a practical approach rather than a fancy one.
The user interface of the instrument is based on a "traditional" LCD display and few push-buttons.
No fancy touch screen with nice graphics.
A lab instrument needs to be first of all simple and immediate to use and sturdy, ANYBODY should be able to use it after 5 minutes and the tools itself must be capable to work in an hostile environments (spills, dirt, etc.)

Alarm

The TeirmiLab should have the capability to generate an alarm if a specific temperature is reached.
The alarm can be visual (change color of the display for example), audio (buzzer) or web based (browser pop up).

Remote display from the sensor

The sensor should be detached from the main unit, i.e. connected via cable.
The thermometer should be placed away (inches) from the source to measure so to easily locally display the temperature on a local display

Local settings

It must be possible to set locally some functionality, like setting an alarm or setting up an offset.
So a mini keyboard with at least three pushbutton is necessary.
Alternatively is possible to use a rotary digital  encoder with a pushbutton.

Keyboard/Keypad

Here a button requirements:

• Mode
  The Mode button allows to change the state of the instrument.
  There are 4 modes :
• Run  (default mode)
  In this mode the temperature read from the sensor is displayed in real time (every second).
  If the alarm is set, the display will show the normal temperature in Green and will switch in Red when the alarm is reached.
• Measurement unit
  By default the measurement unit is in Celsius.
  Alternatively is possible to select Fahrenheit or Kelvin
  The selection of the measurement unit automatically update the current values (alarm/offset)
• Alarm Set
  In this mode is possible to enter the alarm temperature, using other two pushbutton to increment or decrement such value
• Offset Set
  Some sensors can have an offset. This mode allows to add a value to the reading to offset the sensor.
• Increment
  The Increment button (+) allows to increment a value
• Decrement
  The Decrement button (-) allows to decrement a value

Digital Rotary Encoder

The pushbutton on the encode select the mode, then rotating the encoder clockwise will increase a value. Rotating the encoder counterclockwise will decrease a value.

• Mode
  The push button  allows to change the state of the instrument.
  There are 4 modes :
• Run  (default mode)
  In this mode the temperature read from the sensor is displayed in real time (every second).
  If the alarm is set, the display will show the normal temperature in Green and will switch in Red when the alarm is reached.
• Measurement unit
  By default the measurement unit is in Celsius.
  Alternatively is possible to select Fahrenheit or Kelvin
  The selection of the measurement unit automatically update the current values (alarm/offset).
  Rotating the encoder will change the selection
• Alarm Set
  In this mode is possible to enter the alarm temperature, rotate the encoder clockwise or counterclockwise to increase and decrease the alarm temperature
• Offset Set
  Some sensors can have an offset. This mode allows to add a value to the reading to offset the sensor.
• Reset
  This option reset the TeirmiLab in a known configuration
• Unit used : Celsius
• Alarm disabled
• Alarm value = 0
• Offset = 0
• Setting
  When in a specific mode, rotating the encoder clockwise or counterclockwise will change the selection.

Raspberry Pi - reading a DS18S20

One of the most common things for any embedded device is the capability to read temperatures.

Raspberry Pi doesn't has any ADC by default, so unless to hook one, the common way to read temperatures is via digital chips, like the DS 18S20.

The DS 18S20 is a 1-wire protocol chip-set from Dallas.
Fortunately somebody already wrote a bit banging support for the 1Wire protocol used by this chip-set , so it is only matter to connect the chip and enable some kernel modules to do so, at least in Raspbian (Wheezi).

I was able to duplicate the results described in the article RaspberryPI DS1820 without problems.
The example is based on a Perl script using the kernel services.

Here some my extra notes (I don't understand why so many people stopped to draw standard electronic schematics in favor of "cartoon" schematics).

Basic schematic to connect a DS1820 to the Raspberry Pi Gpio port.

Raspberry Pi GPIO pinout

DS1820 pinout

By default (as described in the article) the kernel module capable to handle the 1-Wire is disabled.
As first thing is necessary to enable it.

Open a terminal, then :

• sudo modprobe wire
• sudo modprobe w1-gpio  
• sudo modprobe w1-therm

After that, to test if the DS1820 is ready and connected correctly :

• cat /sys/bus/w1/devices/w1_bus_master1/w1_master_slave_count

The result should be the number of DS1820 connected.

To retrieve the serial number of the chip-sets :

• cat /sys/bus/w1/devices/w1_bus_master1/w1_master_slaves

This is the Perl script used to read a sensor, copied from the article of David Mills,  RaspberryPI DS1820 (read that article for more details and how to read two sensors).

#!/usr/bin/perl

$mods = `cat /proc/modules`; 

if ($mods =~ /w1_gpio/ && $mods =~ /w1_therm/) 

{ 

   print "w1 modules already loaded \n"; 

} 

else  

{ 

   print "loading w1 modules \n"; 

   $mod_gpio = `sudo modprobe w1-gpio`; 

   $mod_them = `sudo modprobe w1-therm`; 

} 

$sensor_temp = `cat /sys/bus/w1/devices/10-*/w1_slave 2>&1`; 

if ($sensor_temp !~ /No such file or directory/) 

{ 

   if ($sensor_temp !~ /NO/) 

   { 

      $sensor_temp =~ /t=(\d+)/i; 

      $tempreature = (($1/1000)-6); # My sensor seems to read about 6 degrees high, so quick fudge to fix value  

      print "rPI temp = $tempreature\n";  

      exit; 

   } 

   die "Error locating sensor file or sensor CRC was invalid";  

}