Description of the 1-Wire Protocol Converter

The CAS-2700-26 Gateway with 1-Wire (AKA 1Wire/OneWire) serial driver translates data between a 1-Wire bus and popular building automation protocols such as BACnet, Modbus, and VeederRoot. For example translating a network of DS18B20 1-Wire temperature sensors to BACnet points for a JCI controller to read, or allowing a controller to interact with a DS2408 1-Wire relay device as if they were a Modbus outputs.


The 1-Wire driver can translate to the following protocols

Modbus RTU


The Gateway connects to the 1-Wire bus, periodically reads data and stores it internally. When a remote system requests data, this data is served in a form that is appropriate to the protocol.  The driver signals the remote client in the event that the connection to a 1-Wire device is lost or data cannot be CRC verified. The Gateway can also accept inputs from client protocols and translate them into write requests to 1-Wire memory and IO devices.

The Gateway can run multiple TCP/IP drivers simultaneously. Multiple RS232 / RS485 drivers cannot be used simultaneously. Drivers can be configured from web interface, but the serial port can only be changed from RS232 to RS485 with an internal jumper.

The Gateway requires minimal configuration and can be considered a plug and play component of your system. It is ready to operate out of the box with the default configuration.




  • UL, ULc, CE, and FCC approved
  • 10/100BaseT with RJ-45 connector
  • 1x RS232 / RS485 Port
  • 2MBytes flash memory, 8MBytes of SDRAM
  • Power: 7-24VDC (90mA @ 12v)
  • Operating Temperature: 0 to 70 C
  • Dimensions: 6.2″ x 3.25″ x 1″
  • LEDs: Link, Speed/Data, Power
  • RoHS Compliant


Max Nodes Supported

Gateway Mode Nodes Comments
Client 100 100x 1-Wire devices per daisy chain.
Server 100 Serve up to 100 devices.


Connection Information – Port 1: 1-Wire

Connection type:

1-Wire RJ11 connector. Open drain interface.

Baud Rates (bps):

4800, 9600, 19200, 57600, 115200

Multidrop Capability Yes
Parasitic Power Yes (up to 200 mA)
OverDrive Capability Yes.
High Power Pullup Yes.


Connection Information-Port 0: RS485/RS232 Port


Connection type: RS485/RS232 (Selectable with internal jumper)
Baud Rates (bps): 9600; 19200
Data Bits: 8
Stop Bits: 1
Parity: None
Hardware interface: N/A
Multidrop Capability Yes


Devices tested

Device Tested (FACTORY, SITE)
DS18B20 (Temperature) Tested


1-Wire Gateway Diagram 1

Picture 1


1-Wire Gateway Diagram 2

Picture 2


Driver Operation

1-Wire device discovery occurs automatically at a configurable period.  The Gateway has an internal record of sensor data which is periodically updated by reading the 1-Wire bus. The frequency at which each data point is read is configurable through the web interface. The driver retries on errors or timeouts. If the data cannot be read or fails the 1-Wire checksum it is marked as out of date or unreliable. When a client protocol makes a read request the gateway serves up its data using the appropriate conversion. When a client protocol makes a write request (for 1-Wire output devices) the Gateway updates its internal records as well as writing the data to the appropriate 1-Wire device and performing a verification.

The driver generates an HTML page which allows status to be checked and setting to be altered from a web browser.


The CAS Gateway supports discovery and self-configuration of 1-Wire devices. A routine to discover new 1-Wire devices is executed at a regular period selectable by the user.

When a new 1-Wire device is discovered a new task is created for this device and its value is added to the end of the database. This task periodically reads/writes information from the 1-Wire device at a user defined period.

The gateway supports BACnet IP, Modbus RTU, Modbus TCP protocols simultaneously.

Communications functions

Sufficient functions have been added to the product to read/write data and status from 1-Wire devices. Other functions can be added on request.


This driver was developed by Chipkin Automation Systems (CAS). CAS are proud to provide support for the driver. For support please call CAS at (866) 383-1657.


Revision History

Date Resp Format Driver Ver. Doc. Rev. Comment
2013Aug15 SWS 1.00 0 Created
2013Aug22 SWS 1.00 1 Added notes about communications functions and updated the connection diagram.
2013Oct2 REK 1.01 2 Added additional information. Modified to be general 1-Wire marketing doc.


1-Wire Links

1-Wire-Design Guide v1.0

Arduino 1-Wire SDK

DS9097U-S09 – Universal 1-Wire COM Port Adapter Datasheet

Powering Extended features of 1-Wire devices


If you liked this post;
  • Please consider subscribing to our RSS feed