OneWire Bridge

Serial bridge for temperature and sensor devices using the OneWire protocol.

Overview

The OneWire Bridge provides direct communication with 1-Wire (OneWire) devices such as temperature sensors, humidity monitors, and smart battery controllers. OneWire is a low-speed, single-wire protocol (plus ground) designed by Maxim Integrated for simple sensor networks.

The bridge communicates directly with a OneWire busmaster device (e.g., DS9490R USB dongle) without requiring the OneWire File System (OWFS). It accesses the native Maxim Integrated C library via Java JNI for optimal performance.

Common use cases: * Temperature monitoring (thermometers at different locations) * Humidity and environmental sensors * Battery voltage and current monitoring via smart battery controllers

Components

Bridge OneWire

Name: Bridge OneWire

Factory-PID: Bridge.Onewire

Purpose: Master bridge for 1-Wire communication with temperature and sensor devices.

Configuration:

  • id (String): Unique bridge identifier; default: "onewire0"

  • alias (String): Human-readable name; default: same as id

  • enabled (Boolean): Enable/disable this component; default: true

  • port (String): OneWire adapter port identifier; default: "USB1"

Supported Devices

Common OneWire Sensors

  • DS18B20 - Digital thermometer (-55°C to +125°C)

  • DS18S20 - Digital thermometer (older model)

  • DS2438 - Smart Battery Monitor (voltage, current, temperature)

  • DS2450 - Quad A/D converter for analog inputs

  • DS2413 - Dual addressable switch

  • DS1923 - Temperature and humidity logger

For complete device list, query the bridge via getDevices() JSON-RPC method (see "Identifying Devices" section).

Hardware Setup

OneWire Adapter

Supported adapters: * DS9490R - USB dongle (recommended, most common) * DS9481 - Serial adapter * Compatible third-party 1-Wire adapters

USB Adapter Setup

  1. Connect adapter to USB port on OpenEMS system

  2. Verify detection: lsusb | grep Maxim

  3. Configure port in OpenEMS config (typically USB1, USB2, etc.)

Serial Adapter Setup

  1. Connect adapter to serial port (/dev/ttyS0, /dev/ttyUSB0, etc.)

  2. Configure permissions: sudo chmod 666 /dev/ttyS0

  3. Set port in OpenEMS config (e.g., "/dev/ttyUSB0")

Native Library Installation

The bridge requires the native 1-Wire library from Maxim Integrated compiled for your system.

Linux Installation

  1. Download OneWireViewer: bash wget https://www.maximintegrated.com/…​/OneWireViewer-Linux.zip unzip OneWireViewer-Linux.zip

  2. Install build dependencies: bash sudo apt-get install libusb-dev build-essential sudo apt-get install openjdk-11-jdk # or appropriate version

  3. Compile native library: bash cd OneWireViewer-Linux/PDKAdapterUSB make sudo make install

  4. Configure exclusive access (DS9490R USB only): ```bash # Unload default Linux driver sudo rmmod ds2490

    # Block driver from loading on boot
echo "blacklist ds2490" | sudo tee /etc/modprobe.d/ds2490.conf
    # Reboot or apply immediately
sudo update-initramfs -u
```

Verification

Test native library loading:

cd /usr/local/lib
ls -la *1Wire*
java -Djava.library.path=/usr/local/lib YourOpenEMSApp

If library not found, check LD_LIBRARY_PATH includes /usr/local/lib.

Device Discovery & Configuration

Discovering Connected Devices

Use the getDevices() JSON-RPC method to identify all connected 1-Wire devices:

Request via OpenEMS Backend:

{
  "method": "edgeRpc",
  "params": {
    "edgeId": "edge0",
    "payload": {
      "method": "componentJsonApi",
      "params": {
        "componentId": "onewire0",
        "payload": {
          "method": "getDevices",
          "params": {}
        }
      }
    }
  }
}

Response Example:

{
  "devices": [
    {
      "address": "4D0000094xxxxxxx",
      "name": "DS18B20",
      "description": "Digital thermometer ...",
      "details": {
        "type": "TemperatureContainer",
        "temperature": 17.5625
      }
    },
    {
      "address": "6F0000022xxxxxxx",
      "name": "DS2438",
      "description": "Smart Battery Monitor ...",
      "details": {
        "type": "TemperatureContainer",
        "temperature": 19.3125
      }
    }
  ]
}

Use the address field to configure individual thermometer components (see io.openems.edge.onewire.thermometer).

Device Addresses

Each 1-Wire device has a unique 64-bit address in hexadecimal format: * Example: 4D0000094xxxxxxx * Format: FFXXXXXXXXXXXXXXXXXX where FF is family code, X is unique serial

Store these addresses for configuring thermometer components.

Source Code