CAN-GW - Ethernet-CAN-RS485 gateway

Linux embedded Wireless access (through GSM mobile phone with GPRS) Joint access of several programs to one CAN port (CAN 2.0b) The remote access to CAN ports Filtration of packages for each connection (independent) Small power consumption Appendix Detailed user's guide Developer's guide(API).

Description

The field buses, like CAN or PROFIBUS are wide used in the industrial control systems. Office PC with appropriate interface card is often used as bus controller in such systems. It is convenient solution , which is not quite optimal :

• There are difficulties in the geographical separation of terminals and controllers (CAN cable length is not more than 1000 m)
• PC has high power consumption
• There are many unreliable elements of mechanics in PC (hard drive, fan)
• The large dimensions of PC box
• The cost of PC with interface card is relatively high
• The narrow ambient temperatures range
• Problems with access of multiple users to one CAN line

The offered device (CanPort) is gateway between telemetric buses (CAN, RS485) and data transmission networks (Ethernet, RS232). GPRS modem can be used for data connection as well. GPRS connectivity can significantly speed up the target system installation in conditions of poor telecom infrastructure.

Gateway is powered by FreeScale RISC processor MPC852 with approximately 48 MIPS. There are 32 megabytes of SDRAM memory and 4 megabytes of flash with the data compression capability. Linux with kernel 2.4 is used as embedded operating system.

There are two alternative application schemes of the gateway. The first is remote CAN interface. The second is programmable logical controller (PLC).

In the first case gateway acts as TCP server and retransmits packets between IP net and CAN line. Client is any workstation in the IP net. Client software resides in the workstation and connects to the server with help of CAN library. Library shadows the client – server exchange complexity from user. So, application software works with library calls like with local CAN interface.

Some times it is not practical to transport all data from sensors. It is more convenient to process sensors information in the CAN gateway. There is possibility to develop C and C++ programs for the embedded gateway system. Some known SCADA systems can be easily adopted for gateway, for example EPICS (see http://www.aps.anl.gov/epics/ ).

CanPort gateway is completed with:

• developer SDK (with cross compiler GCC 3.2, pthread, …)
• Client library for Linux, Windows
• Portable CAN monitor software, which can be used for debugging CAN exchange and messages transmission

Example of application:

Firmware includes:

• OS Linux 2.4 (with iptables)
• Telnet server and client
• FTP server
• HTTP server
• PPP demon
• CAN driver (read, write, select, ioctl)
• Rdate (time synchronization with time servers using NTP protocol)