EPOS4: USB/CAN resp. RS232/CAN Gateway

Topic:

• What has to be considered in case of using the EPOS4's USB/CAN resp. RS232/CAN gateway feature?

Solution:

If there is the gateway feature in use, the master (e.g. PC) commands and exchanges the system's data by one EPOS4 through the USB or RS232 interface. This EPOS4 receives and transmits not just its own commands and data but also forwards these in between all EPOS4s of the CAN network and the master.

Basic requirements:

The EPOS4 gateway functionality demands for a proper wiring and configuration of the required CAN network in between all EPOS4s.

• The basics of the CAN bus topology have to be fulfilled,
  e.g. no star wiring, no stub wires.
• There must be a bus terminator activated or added at both end points of the CAN network.
• Each EPOS4 must have a unique node ID configuration.
• At least one EPOS4 must have a fixed CAN bit rate configuration.
  If more than one EPOS4 has a fixed CAN bit rate configuration, these must be the same.

Restriction:

The EPOS4 gateway is not designed for real time applications. Based on the fact that any communication is processed by the master's and EPOS4's USB or RS232 interface initially (or finally) there is no real time capable PDO based data exchange with the CANopen network devices possible.

Any data exchange of the CANopen network of the EPOS4 gateway is SDO based, i.e. there are requests and replies processed for commanding resp. the exchange of each single object's data content. This communication structure and the SDO based data exchange cannot fulfill real time requirements of a fast periodic and synchronized communication. There have to be typically some milliseconds reaction time taken into account for every single command.

Some general information about the data exchange rates of Windows- or Linux-based master systems as well as maxon's "EPOS Command Library" are discussed by the following linked Support Center article:

• EPOS Command Library: Data exchange rates?

Principle network structure:

The principle hardware setup and configuration has to look like this:

Cross reference:

The basics of a CAN Bus topology, node-ID and CAN bit rate configuration, and bus termination have to be taken into account like for any CAN Bus wiring. These are described by the following linked Support Center article:

• CAN bus topology and bus termination

Note: Attached document

The attached document describes these basics too and provides some more details and screenshots of the CAN bus configuration by EPOS Studio's tools.