Communication

Communication

1. Fieldbus

1. the name of a family of industrial computer network protocols

2. real-time distributed control

3. IEC 61158

Example: (1) Profibus, (2) EtherCAT, (3) Modbus

1.1. EtherCAT

EtherCAT® is an Ethernet-based fieldbus system, invented by Beckhoff Automation.

Standard PC(TwinCAT) <--[TCP/IP]--> EtherCat Master(TwinCAT) <--[EtherCat]--> EtherCat Slave

Standard PC(PyADS) <--[TCP/IP]--> EtherCat Master(TwinCAT) <--[EtherCat]--> EtherCat Slave

http://www.autooo.net/utf8-classid123-id53533.html

http://www.ethercat.org/pdf/cn/EtherCAT_Introduction.pdf

1.1.1. TwinCAT

The TwinCAT software is the master application for EtherCAT.

2. Interface

2.1. Automation Device Specification (ADS)

1. device-independent

2. fieldbus-independent interface

device <-> ADS <-> Message Router (TCP/IP) <-> ADS <-> device

2.1.1. ADS device identification

AdsPortNr:

ADS devices in a TwinCAT message router are uniquely identified by this.

AdsAmsNetId:

Every PC on the network can be uniquely identified by a TCP/IP address, such as "172.1.2.16". The AdsAmsNetId is an extension of the TCP/IP address and identifies a TwinCAT message router, e.g. "172.1.2.16.1.1".

Q&A

1. where are EtherCat Master? @PC, or @plc-controller

2. where is ADS? PC <-> PLC?

Useful link

EasyCat: http://www.bausano.net/en/hardware/ethercat-e-arduino/easycat.html

http://jayextmemo.blogspot.de/2014/09/ethercat-raspberry-pi-asda-a2.html