DS2484 I2C-to-1-Wire Bridge

The DS2484 gives the controller a proper hardware 1-Wire bus, so you can read Dallas devices such as the DS18B20 waterproof temperature probe. This example uses the Adafruit DS2484 I2C-to-1-Wire bridge (I2C address 0x18, Qwiic connector on board).

Bench-tested with real DS18B20 probes

This bridge is verified on real hardware: two DS18B20 probes read at the same time through the DS2484 over Qwiic. The worked example, addresses, and screenshots further down are taken straight from that setup.

Why a bridge instead of a GPIO

ESPHome can bit-bang 1-Wire on a plain GPIO, but the protocol is timing-critical and WiFi interrupts can corrupt a read. The DS2484 runs the 1-Wire timing in dedicated hardware and talks to the ESP32 over I2C, which is far more reliable, especially over longer cable runs. Plug it into the Qwiic connector and it shares the same bus as the onboard HDC1080.

Dallas / Maxim 1-Wire only

The DS2484 speaks the Maxim/Dallas 1-Wire protocol: DS18B20, DS18S20, DS2401 iButtons, and similar. A DHT11/DHT22 uses a different single-wire protocol and cannot be read through this bridge.

Add it to your config

Plug the bridge into the Qwiic connector, then include the module as a package:

packages:
  hardware: ...      # your hardware-rev-*.yaml
  ds2484:
    url: https://github.com/zeroflow/wifi-fancontroller
    ref: main
    files:
      - modules/ds2484_onewire.yaml

That is enough to bring up the bus. The module also adds three diagnostic helpers to Home Assistant so you can find your sensors:

Entity	Type	What it shows
1-Wire Devices	text sensor	Comma-separated ROM addresses currently on the bus
1-Wire Device Count	sensor	How many devices were found
1-Wire Rescan	button	Re-scans the bus on demand

Find your sensors

Every Dallas device has a unique 64-bit ROM address burned in at the factory. You need that address to read the device, and the helpers above are there to hand it to you:

1. Wire your DS18B20 (or other 1-Wire device) to the bridge and power the controller on.

2. In Home Assistant, press the 1-Wire Rescan button.

3. Read the addresses off the 1-Wire Devices sensor. With one DS18B20 connected it shows something like:

   0x28ff641f7016034c

1-Wire Device Count confirms how many devices the bus sees, which is a quick sanity check that all your sensors are wired correctly.

Telling identical sensors apart

DS18B20 probes look identical and their addresses are assigned at random, so the address alone does not tell you which physical probe is which. The reliable method is to connect them one at a time:

1. Plug in a single sensor and press 1-Wire Rescan.
2. Note the one address that appears on 1-Wire Devices, and remember which physical probe it belongs to.
3. Plug in the next sensor, rescan, and note its address.

After that you know exactly which address maps to which probe, and you can give them the right names (for example “Left” and “Right”) when you add them below. 1-Wire Device Count going up by one each time is your confirmation that the new probe was seen.

Add your sensors by address

Once you have the address, add a dallas_temp sensor in your own config (not in the module). Point it at the bus the module created with one_wire_id: ow_bus and set the address you just read:

sensor:
  - platform: dallas_temp
    one_wire_id: ow_bus
    address: 0x28ff641f7016034c
    name: "Water Temperature"
    update_interval: 30s

This is a plain list entry, so it simply merges with the module. You do not need !extend for it. Repeat the block for each additional sensor with its own address. If you run a single device, you may omit address: and ESPHome uses the only one it finds, but setting it explicitly is safer once more than one device might ever be on the bus.

New to the module system?

Adding your own entities, changing module variables, and overriding module entities are three different operations. If any of that is unfamiliar, read How modules work once. It applies to every module, not just this one.

A worked two-sensor example

This is a real, bench-tested setup with two DS18B20 probes on the same bus. Each one was identified with the one-at-a-time method above, so the names match the physical probes:

sensor:
  - platform: dallas_temp
    one_wire_id: ow_bus
    address: 0xf23c01d607613d28
    name: "Right Sensor"
    update_interval: 30s
  - platform: dallas_temp
    one_wire_id: ow_bus
    address: 0x273c01d607763628
    name: "Left Sensor"
    update_interval: 30s

Both values are the exact strings the 1-Wire Devices helper reported (the screenshot near the top shows the same two addresses). Because each dallas_temp block pins its own address, the two entities stay tied to their probes even if you unplug them, replug them, or change the wiring order.

Configuration variables

Set these under the package’s files: entry with vars: (see the full example below), or as top-level substitutions: in your config.

Variable	Default	Purpose
ow_prefix	1-Wire	Prefix for the helper entity names, for example Aquarium Devices
ow_update_interval	60s	How often the helper text/count sensors refresh

IDs you can override

These are the component IDs the module defines. They are the surface you can reach with !extend and !remove from your own config.

ID	Type	Notes
ow_bus	one_wire (ds2484)	The 1-Wire bus. Attach dallas_temp sensors with one_wire_id: ow_bus.
ow_device_list	text_sensor	The “Devices” helper
ow_device_count	sensor	The “Device Count” helper
ow_rescan	button	The “Rescan” helper

For example, to drop the diagnostic helpers once your sensors are configured and you no longer need them:

text_sensor:
  - id: !remove ow_device_list
sensor:
  - id: !remove ow_device_count

Or to change the bus, for instance a board that sits at a different I2C address:

one_wire:
  - id: !extend ow_bus
    address: 0x19

Bus and prerequisites

• Requires the hardware package (it provides the shared I2C bus bus_a). This module is not standalone.
• I2C address: 0x18, fixed by the module. The Adafruit board ships at 0x18. If your board is jumpered to a different address, override it with !extend ow_bus as shown above.
• Bus speed: this module does not change the shared bus speed. The DS2484 works fine at the default, and the bus is shared with the onboard HDC1080 and any other Qwiic device. If you want a faster bus for another module, raise it yourself with !extend bus_a. See Combining Expansion Modules.

Web UI grouping

This block goes in your own configuration, not in the module. See why the assignment lives in the consuming config for the reason. version: 3 is what makes entity grouping work at all; without it, entity grouping has no effect.

web_server:
  version: 3
  sorting_groups:
    - id: grp_ds2484_onewire
      name: "1-Wire Bus"
      sorting_weight: 330

button:
  - id: !extend ow_rescan
    web_server:
      sorting_group_id: grp_ds2484_onewire
      sorting_weight: 10

text_sensor:
  - id: !extend ow_device_list
    web_server:
      sorting_group_id: grp_ds2484_onewire
      sorting_weight: 900

sensor:
  - id: !extend ow_device_count
    web_server:
      sorting_group_id: grp_ds2484_onewire
      sorting_weight: 910

The group id is fixed rather than built from ow_prefix at config time. ow_prefix is a display name whose default value, 1-Wire, contains a hyphen and cannot appear in an ESPHome id, and this module hard-codes its bus id (ow_bus) and I2C address (0x18), so a second instance is not a supported configuration for it in the first place.

Full example

A complete, compilable config: the hardware package, this module with a renamed helper prefix, and one DS18B20 read by address.

substitutions:
  wifi_ssid: "YourNetwork"
  wifi_password: "YourPassword"

packages:
  hardware:
    url: https://github.com/zeroflow/wifi-fancontroller
    ref: main
    files: [hardware-rev-3.1.yaml]
  ds2484:
    url: https://github.com/zeroflow/wifi-fancontroller
    ref: main
    files:
      - path: modules/ds2484_onewire.yaml
        vars:
          ow_prefix: "Aquarium"
          ow_update_interval: "60s"

esphome:
  name: my-fancontroller
  friendly_name: My Fan Controller

esp32:
  board: esp32-s2-saola-1
  framework:
    type: arduino

logger:
api:
ota:
  - platform: esphome
wifi:
  ssid: ${wifi_ssid}
  password: ${wifi_password}
  ap:
    ssid: "Fancontroller Fallback"
captive_portal:

# Your own sensor, added by the address the "Aquarium Devices" helper reports.
sensor:
  - platform: dallas_temp
    one_wire_id: ow_bus
    address: 0x28ff641f7016034c
    name: "Water Temperature"
    update_interval: 30s