Homekit, temperature with DS18B20

Updated 2021-04-15 !

A cheap and simple way to measure temperature, and have it displayed in the Home app, is to connect one wire (1W) DS18B20 (DS)temperature sensors direct to the Raspberry Pi(RPi) and install a DS plugin.

This assumes that You have Homebridge up and running on a Raspberry Pi 

Check this post !!  "ANY" temp source can be HomeKit enabled.

Basic setup
Enabling 1W

Start with enabling the 1W interface on the RPi, in a terminal session, editing the config file with 

$ sudo nano /boot/config.txt

add 

dtoverlay=w1-gpio

at the end of the file. (If it is not already there)

Shutdown the RPi with 

$ sudo shutdown -h now

Connect the DS
Disconnect the power and connect, to the header pins(HP), one or several DS according to the picture. 

Red     HP 1, +3,3 V
Yellow  HP 7, Data
Black   HP 9, Ground

RPi 1-Wire pinout is discussed here

Check the DS
Connect the power and start a terminal session with command

$ ls  /sys/bus/w1/devices/
28-051693ec41ff  w1_bus_master1

One or several "28-" folders will show and this corresponds to the connected DS id. 
In every "28-" folder there will be a file w1-slave which holds the actual temperature.

So checking the connected DS:s temperature, type

cat /sys/bus/w1/devices/28-051693ec41ff/w1_slave
7f 01 4b 46 7f ff 0c 10 ba : crc=ba YES
7f 01 4b 46 7f ff 0c 10 ba t=23937

the last row holds the value "23937" which should be divided with 1000, so the temperature is 23,937 degrees Celsius and the installation is OK.

Alternative connection
In my case I have a Razberry Z-wave-controller installed on the RPi and this board covers the header pins 1-16. Therefore we move the default 1W input from GPIO 4, HP 7, to GPIO 24, HP 18, by changing the 1W configuration in /boot/config.txt to 

dtoverlay=w1-gpio,gpiopin=24

So instead connect the DS cables to

Red     HP 17, +3,3 V
Yellow  HP 18, Data
Black   HP 20, Ground

If You want more than one 1W input, for example also using GPIO 25, just change the config to 

dtoverlay=w1-gpio,gpiopin=24,gpiopin=25

Homebridge plugin installation
The plugin is installed via the UX interface or manually with

$ sudo npm install -g homebridge-ds18b20

and then You have to edit the homebridge configuration file .hombridge/config.json  adding the DS id as an accessory.

So with the DS id

28-051693ec41ff 

add the information

"accessories": [
 {
  "accessory": "DS18B20",
  "name": "Temperature Sensor",
  "device": "28-051693ec41ff"
 }
],

The name "Temperature Sensor" will appear in the Home app so change it to something useful and then do a restart  with

$ sudo reboot

If You done the all things right the temperature will show in the Home app.

The link to the Telldus and Z-Wave setup and below my complete config.json 

{
  "bridge": {
   "name": "Homebridge",
   "username": "CC:22:3D:E3:CE:30",
   "port": 51826,
   "pin": "031-45-154"
  },
  "description": "Z-Wave and Telldus Live plugin",
  "accessories": [
   {
    "accessory": "DS18B20",
    "name": "Temperature Sensor",
    "device": "28-051693ec41ff"
   }
   ],
   "platforms": [
    {
     "platform": "ZWayServer",
     "url": "http://localhost:8083/",
     "login": "admin",
     "password": "admin"
    },
    {
     "platform": "Telldus",
     "name": "Telldus Liv!e",
     "public_key": "FExxxxxxxUNU",
     "private_key": "ZUXxxxxxxxxxx6EF",
     "token": "88xxxxxxxxx0b7d",
     "token_secret": "a57xxxxxxxxxxxd5f"
    }
   ]
 }

And a link to update the Homebridge installation.

HB autostart at power on and failure, installed with a script !! , is found here.

Other HomeKit posts on this Blogg