1-Wire


The onewire platform supports sensors which that using the One wire (1-wire) bus for communication.

Every 1-wire device has a (globally) unique ID that identifies the device on the bus. The first two digits identify a device family and the last 14 digits are a globally unique number given to it during manufacturing.

Different families have different functionality and can measure different quantities.

Supported devices:

Family Device Physical Quantity
10 DS18S20 Temperature
12 DS2406(TAI-8570) Temperature (pressure when using TAI-8570)
1D DS2423 Counter
22 DS1822
26 DS2438/B1-R1-A/S2-R1-A Temperature, Voltage, Current, (pressure and humidity when using TAI-8570)
28 DS18B20 Temperature
3B DS1825 Temperature
42 DS28EA00 Temperature
EF HobbyBoard Temperature, Humidity, Moisture

Notes:

  • The TAI-8570 Pressure Sensor is based on a 1-wire composite device by AAG Electronica. It contains, above 1-wire components, also a barometer, hygrometer and illuminance sensors. This onewire platform can read and present values from that device.

  • Each 1-wire component data sheet describes the different properties the component provides. The owfs software adds some extra tools to make it easier for DIY implementers to use the component. By hobbyists, it is quite common to use DS2438 Smart Battery Monitor as a multipurpose measurement node that can place temperature, humidity and luminosity on the 1-wire bus by just adding some standard components to the DS2438. For different component types, there are ready-made algorithms implemented in owfs. Those are exposed by the owfs software and can be read by this platform. The B1-R1-A/pressure is exposed as a barometric pressure sensor. S2-R1-A/illuminance is presented as an illuminance sensor. For a more detailed description of these properties, refer to the owfs documentation. For this component, the more basic quantities temperature, VAD, VDD and IAD is exported as separate sensors.

  • Hobbyboards is a company that has been selling DIY boards of different kinds. The company has been away from the market for some time, so no reference to the boards can be made. This platform has an implementation for some of those.

Interfacing with the 1-wire bus

The 1-Wire bus can be connected directly to the IO pins of Raspberry Pi or by using a dedicated interface adapter, for example DS9490R or adapters based on DS2482-100 that can be directly attached to the IO pins on the Raspberry Pi.

It is also possible for this platform to interface with a remote 1-wire host over a network connection using ofws and owserver.

Raspberry Pi set up

In order to setup 1-Wire support on Raspberry Pi, you’ll need to edit /boot/config.txt. This file can not be edited through ssh. You have to put your SD card to a PC, and edit the file directly. To edit /boot/config.txt on the Home Assistant Operating System, use this documentation to enable SSH and edit /mnt/boot/config.txt via vi.

If you use an external pull-up resistor and the default GPIO 4 for the data line, add the following line:

dtoverlay=w1-gpio

If you don’t want to use an external resistor, you can use a built-in one using the following line:

dtoverlay=w1-gpio-pullup

It is also possible to use a different GPIO pin like this to change it to pin 15:

dtoverlay=w1-gpio-pullup,gpiopin=15

Furthermore, it is also possible to have multiple GPIOs as one-wire data channel by adding multiple lines like this:

dtoverlay=w1-gpio-pullup,gpiopin=15
dtoverlay=w1-gpio-pullup,gpiopin=16

You can read about further parameters in this documentation: Raspberry Pi Tutorial Series: 1-Wire DS18B20 Sensor.

When using the GPIO pins on Raspberry Pi directly as a 1-wire bus, the description above uses two kernel modules. 1w_gpio, that implements the 1-wire protocol, and 1w_therm, that understands the DS18B20 (family 28) components inner structure and reports temperature. There is no support for other device types (families) and hence this onewire platform only supports temperature measurements from family 28 devices.

Raspberry Pi checking connected devices via ssh

If you set up ssh, you can check the connected one-wire devices in the following folder: /sys/bus/w1/devices The device IDs begin with 28-.

Interface adapter setup

owfs

When an interface adapter is used, sensors can be accessed on Linux hosts via owfs 1-Wire file system. When using an interface adapter and the owfs, the mount_dir option must be configured to correspond to a directory, where owfs device tree has been mounted. On systems where Home Assistant runs in a Docker container. owfs cannot escape that environment and hence cannot populate the mount_dir. Use the owserver method on these systems instead.

owserver

When an interface adapter is used, you can also access sensors on a remote or local Linux host that is running owserver. owserver by default runs on port 4304. Use the host option to specify the host or IP of the remote server, and the optional port option to change the port from the default.

Configuration

To enable One wire sensors in your installation, add the following to your configuration.yaml file:

# Example configuration.yaml entry
sensor:
  - platform: onewire

Configuration Variables

namesstring(Optional)

ID and friendly name of your sensors.

mount_dirstring(Optional)

Location of device tree if owfs driver used.

hoststring(Optional)

Remote or localhost running owserver.

portinteger(Optional, default: 4304)

The port number of the owserver (requires host).

Configuration Example

When onewire is added to Home Assistant, it will generate an ID for the sensor. You can specify a friendly name for the sensor with the name configuration option.

# Named sensor configuration.yaml entry
sensor:
  - platform: onewire
    names:
      GENERATED_ID: FRIENDLY_NAME

Entities and attributes

Upon startup of the platform, the 1-wire bus is searched for available 1-wire devices. For each device that this platform handles (see list of supported devices above), the platform adds one sensor for each physical quantity it measures. The name of the sensor is the device ID with the physical quantity it measures appended.

sensor.28.FF5C68521604_temperature

Each sensor will present its value in the state variable and for presentation purposes, rounded to one decimal for analog values and as integers for counts.

Each sensor also exposes some additional attributes.

device_file: /28.FF5C68521604/temperature              << Device path in owfs file system (or on Rpi system directory)
raw_value: 31.9375                                     << The raw measurement numbers as red from device. Not rounded.
unit_of_measurement: °C                              
friendly_name: 28.FF5C68521604 Temperature

Units with multiple sensors

This platform works with devices with multiple sensors, which will cause a discontinuity in recorded values. Existing devices will receive a new ID and therefore show up as new devices. If you wish to maintain continuity, it can be resolved in the database by renaming the old devices to the new names.

Connect to your database using the instructions from Database section. Check the names of sensors:

SELECT entity_id, COUNT(*) as count FROM states GROUP BY entity_id ORDER BY count DESC LIMIT 10;

Alter the names of sensors using the following examples:

UPDATE states SET entity_id='sensor.<sensor_name>_temperature' WHERE entity_id LIKE 'sensor.<sensor_name>%' AND attributes LIKE '%\u00b0C%';
UPDATE states SET entity_id='sensor.<sensor_name>_pressure' WHERE entity_id LIKE 'sensor.<sensor_name>%' AND attributes LIKE '%mb%';
UPDATE states SET entity_id='sensor.<sensor_name>_humidity' WHERE entity_id LIKE 'sensor.<sensor_name>%' AND attributes LIKE '%%%' ESCAPE '';

Remember to replace <sensor_name> with the actual name of the sensor, as seen in the SELECT query.