Raspberry Pi and DS18S20 temperature measurement

This page records some work on using DS18S20 with Raspberry Pi and plotting using AWK, SVG and JavaScript.

Using the kernal extensions ( see links ) the Raspberry Pi can use the "one wire" interface to read the Dallas 18S20 temperature chips.

I use a shell script to poll the chips and append the readings to a file of JavaScript function calls and other text files.

An awk script is used to extract the text and populate the gbF() function calls. If written to a file, the file can be included into an SVG file.

Using JavaScript in an SVG file, I plot the data as a simple graph. The SVG file does a location.reload() to update.

This is run in the Midori 0.4.3 web browser that renders the SVG file.

example: http://www.dougrice.plus.com/raspberryPi_ds1820/loopDS18S20reportSVG.svg

files: http://www.dougrice.plus.com/raspberryPi_ds1820/

Raspberry Pi and DS18S20

One wire - DS18S20 reader

Used GPIO4 pin 7 - middle pin. 3v3 to power gnd to gnd

		/ 3v3  	
DS18S20	- top (|- buss --GPIO4--[4k7]--/
	  	\ gnd

Web pages to help:-

http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/hardware

http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/ds18b20

Shell Script - loop.sh

The script below starts the kernel module for "OneWire" and loops polling all the devices onthe Bus.

I have 4 DS18S20, which I read and set userfield1,userfield2,userfield3,userfield4 parameters in gbF() guestbook Function. This is appended to gbookFtemp.js on the desk top. The date is set to when I read the devices.

#! /bin/bash
#	
#  Shell Script to poll temperature chips 
#  usage:	 bash loop.sh
#
# http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/hardware
#
echo "---------------------"
ls /sys/bus
echo "---------------------"
sudo modprobe w1-gpio
sudo modprobe w1-therm

echo "---------------------"
ls /sys/bus
echo "---------------------"

while [[ 1 ]]
do
  echo "========" 		    > ~/Desktop/tmp.txt
  date 				   >> ~/Desktop/tmp.txt
  cat /sys/bus/w1/devices/10-*/name >> ~/Desktop/tmp.txt
  cat /sys/bus/w1/devices/10-*/w1* >> ~/Desktop/tmp.txt
  echo " "			   >> ~/Desktop/tmp.txt
  #
  # use AWK to extract the temperatures. appends gbF() to gbookFtemp.js
  #
  cat ~/Desktop/tmp.txt
  awk -f loop.awk ~/Desktop/tmp.txt 

  cat ~/Desktop/tmp.txt >> ~/Desktop/loop_log.txt
  sleep 3 
  
done

Awk Script loop.awk

This awk script extracts the temperature and puts the results into the javascript include file.

#
#
# loop.awk
#
# usage: 	awk -f loop.awk loop_log.txt
#
#
# pull out the temperature from loop_log.txt written by loop.sh 
# Appends to "gbookFtemp.js"
#
#
#//gbF( name,email,postedOn,IPaddress,userfield1,userfield2,userfield3,userfield4,comments){


BEGIN {
  FS="="

  # zero the temperatures
  ln[1]=0
  ln[2]=0
  ln[3]=0
  ln[4]=0
  # print "" > "gbookFtemp.js"
  notFirst = 0
}

/====/{
  print $0
  getline
  print $0
  
  lnp=1
  cnt +=1
  if ( notFirst ){
    print "gbF( 'awk','t@pi','" lastDate " ','127.0.0.1'," ln[1] "," ln[2] "," ln[3] "," ln[4] ",'comments');" >> "gbookFtemp.js"
  }
  # prepare for next readings
  notFirst = 1
  ln[1]=0
  ln[2]=0
  ln[3]=0
  ln[4]=0
  lastDate = $0
}

/t=/{
  # found a line with a temperature
  ln[lnp] = ($NF/1000) 
  lnp ++
}

END {
  cnt +=1
  print "gbF( 'awk','t@pi','" lastDate " ','127.0.0.1'," ln[1] "," ln[2] "," ln[3] "," ln[4] ",'comments');" >> "gbookFtemp.js"
}

some "gbookFtemp.js"

The temperatures are saved wrapped in a function call.

gbF( 'awk','t@pi','Sun Feb  9 10:30:47 UTC 2014 ','127.0.0.1',17.375,18,17.5,17.312,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:30:53 UTC 2014 ','127.0.0.1',17.312,18,17.5,17.312,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:00 UTC 2014 ','127.0.0.1',17.375,19.187,17.562,17.375,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:06 UTC 2014 ','127.0.0.1',17.375,19.187,17.562,17.437,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:13 UTC 2014 ','127.0.0.1',17.437,23.25,17.562,17.5,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:20 UTC 2014 ','127.0.0.1',17.437,24.375,17.625,17.562,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:27 UTC 2014 ','127.0.0.1',17.5,25.375,17.687,17.562,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:33 UTC 2014 ','127.0.0.1',17.5,26.062,17.687,17.562,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:40 UTC 2014 ','127.0.0.1',17.5,26.687,17.687,17.625,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:46 UTC 2014 ','127.0.0.1',17.562,27.562,17.75,17.625,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:53 UTC 2014 ','127.0.0.1',17.562,28.437,17.75,17.687,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:31:59 UTC 2014 ','127.0.0.1',17.625,28.937,17.75,17.687,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:32:06 UTC 2014 ','127.0.0.1',17.625,-1.25,17.812,17.687,'comments');
gbF( 'awk','t@pi','Sun Feb  9 10:32:13 UTC 2014 ','127.0.0.1',17.625,29.5,17.812,17.687,'comments');

SVG - loopDS18S20reportSVG.svg

The SVG below includes the readings in gbookFtemp.js and plots them.