Optical CAN/VAN OBE519 and OBE898 extenders
By OCE we mean a family of fibre optic links for extension of CAN and VAN buses.
The CAN (Controller Area Network) is a bidirectional data stream standardized by ISO specifications.
It is already popular nowadays with the automotive community as it represents the typical connection between on board controllers that exchange data. The need for passing data to and from microprocessor based units on vehicles is growing rapidly and the CAN will get even more popular in the future.
The usage of the bus is also expanding to other application areas requiring relatively high bit rates at a cheap price like industrial automation, intelligent home, etc...
Different speeds are accounted for by different standards.
Low data rates are covered by ISO 11519 part 2 and high data rates by ISO 11898.
OBE519 and OBE898 are TESEO ISO compliant fiber optic extenders.
The differences are confined to the transceivers and, in particular, to few components in the transceiver circuitry.
The reasons for utilizing a CAN bus optical extender in an EMC hostile environment are more than one:
- you may have part of the bus and attached equipment in the chamber being radiated from an antenna and part of same bus and related equipment to be kept out of the high field zone in the control room
- you may need to monitor and/or stimulate the bus during an immunity test from a remote terminal unit outside the anechoic chamber (CAN analyser)
- you have to isolate a portion of the bus
For the above and other possible cases the solution is the extension of the CAN bus by means of the OCE.
The VAN standard is covered by ISO specification 11519 part 3.
The ISO compliant TESEO product is OBE519VAN. Again the differences are confined to the transceivers.
The reasons for utilizing a VAN optical extender are the same as those explained above for CAN.
Each extender consists of:
- two identical Rx/Tx units. They are shielded and battery powered to be independent from the bus power source, for example the vehicle battery. The part number of each unit is OBE519, OBE519-F (Special version compliant with FIAT standards), OBE898 or OBE519VAN.
- two battery chargers, model CB1, to recharge the OBE internal battery
- a bifiber cable, part number FBxxx, with xxx equal to the length expressed in meters. The standard cable is the 10 meters long FB010
The connections of the OBE’s to the electrical bus are a customer’s responsibility.
The use of short twisted shielded wires is recommended.
OLE Series Optical lin extenders
By OLE (Optical Lin Extender), we mean a fiber optic link employed to extend a LIN bus.
LIN is an acronym for Local Interconnect network that is a low cost, low speed, serial communication bus for distributed electronic systems on board a vehicle. It is a sort of complement to other buses like CAN that are used for faster or more demanding applications. It is a one-wire bus and typically it connects in a very cost effective way smart sensors and actuators where bandwidth and versatility of CAN connections are not necessary.
The need for a fibre optic extension of LIN may arise mainly for the performance of immunity tests in an anechoic chamber.
In such case the EUT attached to LIN network must be radiated by a transmitting antenna while the LIN analyser or any other component appended to the LIN (Auxiliary Test equipment) is placed outside of the radiated zone, normally in the control room. The decoupling between EUT and Auxiliary Test Equipment is easily achieved by means of a fibre optic cable inserted between two transceivers that transform the electrical signal into an optic signal and vice versa. As EMC automotive tests require high field levels, at least the transceiver placed in the chamber close to the EUT must be RF shielded.
An extender consists of:
- Two identical transceivers (RX/TX units) called OBE-LINs. Each unit is shielded and configurable through a manual switch to the LIN master or slave standard. The OBE-LIN does not contain any battery. The OBE-LIN unit that is inside the chamber is supplied by the EUT 12 VDC positive battery node (VBAT, GND). The OBE-LIN unit that is outside the chamber is supplied by a 12VDC dedicated power supply.
- One OBE-LIN-ALIM power supply; 110/230Vac mains supply, 12VDC, 0,5A, to supply the OBE-LIN unit that is outside the chamber. The VBAT, LIN bus and GND pins are available on the DB9 Female connector for user connections.
- A bifibre cable FBxxx, with xxx equal to the length expressed in meter. The standard cable is FB010, 10 meter long. The fibre connectors are ST type and the fiber cable is sized 200/230 um.
- Two DB9 female connectors that the customer may use for its connections. The electrical cable between the EUT and the nearby OBE-LIN is the responsibility of the customer. In the presence of the radiating field the connection is critical and must be short.