DeviceNet
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DeviceNet is a communication protocol used in automation industry to interconnect devices such as sensors and actuators. It uses Controller Area Network as the backbone technology, and defines strong application layer to cover a vast range of device profiles.
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[edit] History
DeviceNet was originally developed by an American company Allen-Bradley (now known as Rockwell Automation). It was adapted from its another protocol - ControlNet. ControlNet is a more complex, higher performance, and more expensive protocol. The reason of this adaptation is obvious: CAN silicon is much cheaper than the ControlNet ASIC silicon due to the large quantity sold to the automotive industries.
In order to promote the use of DeviceNet worldwide, Rockwell Automation has adopted the "open" concept and decided to share the technology to third party vendors. Hence, it is now managed by the Open DeviceNet Vendors Association (ODVA), an independent organisation located in the North America. ODVA tries very hard to merge the DeviceNet protocol back into its origin, ControlNet, together with Rockwell Automation's another Ethernet based protocol, EtherNet/IP (stands for Ethernet Industrial Protocol, do not confuse with "Internet Protocol"), under one umbrella named the "Common Industrial Protocol", CIP, which originally stands for "Control and Information Protocol".
[edit] Technical Snapshot
- Defines the Media, Physcal, Data-Link, and Application layers of the ISO/OSI 7-layer model
- Bus (trunk) topology, with up to 6 metres of stub (drop)
- Baudrates defined: 125, 250, and 500 Kbps
- Trunk length is inversely proportional to the speed, i.e. 500, 250 and 100 metres respectively
- A not-so new flat cable was added to the specification to allow the use of the quick-fix connector. The range, however, is limited to 75 metres regardless
- Up to 64 nodes on a single logical network
- Supports master/slave as well as peer-to-peer communication, although majority of the devices work as slave
- Allows multiple masters on a single logical network
[edit] Conformance Test
To declare your product as DeviceNet conformant, a vendor needs to send their product to the ODVA test lab for the certification. ODVA used to have a few other test labs around the world, i.e. UK, Japan, and China. Is has now been consolidated into one that is in the North America.
A full-test version is called the Composite test. It consists of:
- Conformance test. Test against the protocol specification.
- Interoperability test. Test against devices from various vendors on a single, fully populated, network.
[edit] Conformance Test Procedure
The following procedure shows you how to get your product certified.
- Register as vendor with ODVA. You will be given a vendor ID.
- Puchase a copy of the DeviceNet specification. A hard and soft copy will be sent to you.
- Puchase the conformance test software and corresponding hardware interface card. Note that only selected interface cards from a few vendors can be used.
- Develop and test product in-house. You would probably need help from the discussion group, see the External links below.
- Submit your product to ODVA test lab for independent verification.
- Repeat the above two steps until your product successfully pass the independent test.
