Fieldbus. Introduzione terminologia. Industrial network systems. A short introduction to fieldbus for industrial applications. Systems interconnection

Transcript

1 Fieldbus Industrial network systems A short introduction to fieldbus for industrial applications Introduzione terminologia Systems interconnection Es. The OSI model (not mandatory) LAYER FUNCTION EXAMPLES Application network process to application FTP, HTTP, Telnet Presentation encryption, platform.independency,etc. MIME Session interhost communication management SOCKS, NetBIOS, RTP Transport end-to-end conn., flow control TCP, UDP Network path determination, logical addressing IPv4, IPv6, AppleTalk Data link physical addressing IEEE 802.3, (ex 100BASE-T2), ATM, Physical signal binary transmission RS232, IEEE 802.3, USB, BlueTooth,.. 1

2 Introduzione terminologia Parallel ports, bit banging, etc. not used anymore Serial chip-to-chip communication only on a PCB, or very small distances SPI - single master, multiple slaves, - select n-th slave using n-th DIO pin. I 2 C - single master, multiple slaves, - 7 bit for address: 128 nodes (slaves) - speed: 10kbit/s or 100kbit/s, recently also up to 3.4Mbit/s TX/RX (UART) need transceiver for long distance see RS232 etc. Introduzione terminologia Serial communication, higher distances RS232 - logic level up to +25V-25V - speed: up to 115,200 bit/s, - single ended; 1 master, 1 slave - bits: Data/Parity/Stop, typical 8/N/1 RS422 - differential signals (twisted pairs) - for industrial applications, long distances, immune to noise - asynchronous Tx Rx, or not - data protocol: it depends on the implementation RS485 - similar to RS422, but also with multiple slaves, etc. - can be used as a fieldbus (multidrop config.) - example: physical layer of PROFIBUS Optical fiber - larger distances (ex. SC, ST, V-PIN connectors) USB, FireWire,..- not so used for industrial automation (v. realtime, determinism) Bluetooth, ZigBee, Zwave, IrDA, etc. - wireless comm., ex. for domotics or low freq. remote sensor logging, but not for motion control etc. because not deterministic; latencies, losses,.. 2

3 Bus di campo (fieldbus) Main fieldbuses used in automation PROFIBUS MODBUS EtherCAT Ethernet/IP POWERLINK PROFINET SERCOS III DeviceNet EtherCAT Idea: use Ethernet Problem: shortest Ethernet frame = 84 bytes.. What if 100+ slaves? Solution: pack multiple slave data in a single Ethernet frame 3

4 Speed: 1, 10, 100Mbit/s (.. 1Gbit/s) Example: update time for 1000 distributed I/Os is only 30 µs. topology: line (bus), tree or star Different types of wires/connectors (layers), ex. Ethernet (100 Base TX) Copper, CAT 5 (100 m) Ethernet (100 Base FX) Fiber optic (100 km) Up to devices can be connected, 4

5 Can coexist with standard Ethernet (TCP/IP, etc) Master do not need special hardware: use default Ethernet board! Slave can use custom communication microprocessors CAN - Controller Area Network Widely used in automotive field (also in automation, aerospace, etc.) Principle: broadcast to all slaves Slaves understand if the frame is important for them 5

6 Topology: line Requires termination resistance CAN data frame Each node has an ID (to assign with jumpers) Max speed 1Mbit/s 6

7 CAN baudrate 7