A Controller Area Network Layer for Reconfigurable Embedded System

1. A Controller Area Network Layer for Reconfigurable Embedded System Nithyananda Siva Jeganathan Masters Thesis Defense Department of Electrical and Computer Engineering University of Kentucky Lexington, KY October 3, 2007

2. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

3. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

4. Thesis Motivation • All safety-critical distributed systems need a reliable network for communication • The embedded network should also be fault-tolerant • Operate with limited services during faults and degrade gracefully in case of failures

5. Background • Reconfigurable distributed Apps. • Ideal platform for fault-tolerant systems • Faults will always occur • system should detect/isolate faults • Ardea is the reference framework • IDEAnix Framework • ENDURA network layer IDEAnix Framework (cont …)

6. ARDEA Background Direction Graph • ARDEA Architecture • Framework for dynamic reconfiguration using Direction Graphs (DGs) • Supports Graceful degradation • Relies on Broadcast network for sending data between nodes • IDEAnix Framework • Provides application layer with features for reconfiguration • Handles packet routing between nodes/ modules

7. Challenge • How to implement a reliable network driver that supports fault-tolerance? • How to make the implementation efficient? • What services to provide to make the network layer generic?

8. Thesis Objective • Embedded Network Driver for Use on Reconfigurable Architecture (ENDURA) • Network Interface task using Controller Area Network (CAN) • Broadcast type network with dynamic registering or unregistering of messages • ENDURA layer implementation is generic • Designed to match standard API calls • CAN layer can be replaced by any broadcast type network

9. Embedded Network Overview • Most embedded networks use ISO/OSI layer architecture • Data communication protocol • Node oriented communication • Message oriented communication • Medium Access Control (MAC) • CSMA/ CD • CSMA/ CA

10. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

11. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

12. CAN Background • CAN standard invented by Bosch GmbH for Automobiles in 1980s • CAN protocol standardized in Data Link layer and MAC layer • ISO standardized the protocols • ISO 11898-1:CAN type A (11 bit Msg Ids) • ISO 11898-2:CAN type B (29 bit Msg Ids) • ISO 11898-3 : Time Triggered CAN (TTCAN) • Maximum Payload of 8 bytes • Maximum Bandwidth 1 MBits/Sec for distance 40 meters

13. CAN Background • It is widely used in embedded networking • Many standardized Higher level protocols • CANOpen • DeviceNet • CANAerospace • Differential 2-wire signaling • EMI resistant • Fault detection/ Isolation techniques included

14. CAN Applications Overview • Small Vehicle Applications • Light Electric Vehicles (LEVs) • Marine Applications • SeaCAN architecture • NAUTILE • Space Applications • SMART-1 satellite of ESA • SOPIA • Galileo Projects

15. CAN Hardware • Variety of CAN hardware available in market • CAN Controllers • CAN transceivers • CAN cables • CAN Repeaters • CAN Connectors • There are at least 50 known manufacturers of CAN hardware

16. CAN Hardware • CAN Physical layer • ISO 11892- 2 two-wired balanced signaling • ISO 11893- 3 (two-wired) for lower speeds. • Fault tolerant • even if 1 wire is shorted to ground or cut can communicate • There is a single wire (plus ground) standard SAE j2411 for cars • Different Physical Layers as a rule, cannot interoperate • No. of Transceivers are available to make them work (sometimes)

17. CAN Hardware • CAN Transceivers • Used as an interface between CAN Bus and Controllers • Provides differential Tx capability to bus and differential Rx capability to CAN Controllers • CAN Cables • 9 pin D-sub (most common) • CAN Adaptors • Repeaters • Allow physical coupling of two or more segments of CAN Bus • Bridges • Networks different bit rates and protocols • Gateways • Enables access to other Communication networks • CANlinkII, Can@Net, CANmodem/CANOpen

18. CAN Controllers • CAN Protocol Controllers • Responsible for the protocol adherence of the bus • Responsible for Tx/Rx of Messages and RTRs • The number of Message objects available varies for manufacturers • Some companies: Bosch, Intel, Infineon • Bosch’s C_CAN processors are widely used • At least 30 known manufacturers of CAN controllers

19. Microcontrollers with CAN • Microcontrollers with CAN capabilities are the reason for widespread use of CAN • Some of the well known manufacturers • Silicon Laboratories (C_CAN chip) • Fujitsu Semiconductors (C_CAN chip) • OKI Semiconductors (C_CAN chip) • Intel Technologies (82527 chip) • Infineon Technologies

20. Silicon Laboratories • Implements CAN protocol using Bosch’s C_CAN protocol controller chip • 8051 based 8-bit Microcontroller • Has 32 Message Objects that can be configured for Rx/Tx • Supports speed upto 1 Mb/s • 9 pin D-sub connectors are used

21. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

22. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

23. CAN Protocol Overview • CAN is broadcast type network • All nodes receive all the messages • Message filtering option on processors • CAN bus is Wired-AND logic • Dominant bit is 0V & Recessive bit is +5V • If one node is transmitting 0, then the network is in that state (All other processors transmit a 1) • Acceptance Filtering is key to message Rx • Based on Message identifiers • Tx on network in Big-Endian format

24. CAN Protocol Overview • CAN bit-timing uses NRZ encoding • Neither CSMA/CD or CA is used in synchronization of bus • Bit-timing is crucial to synchronized packet transfer

25. CAN Packet Formats • CAN Data Frame • Normal packet transfer • 8 byte payload • CAN Remote Frame • Remote Request/ Response • Similar to ICMP messages • CAN Error Frame • CAN Overload Frame

26. CAN Frame Format

27. ENDURA Design Details • The ENDURA layer is a generic network implementation for Reconfigurable architecture • ENDURA layer for CAN is modularized as: • Initialization module • Register module • Unregister module • Send Packet module • Receive Packet module • Translation module • Interrupt service routine module

28. ENDURA Block Diagram

29. ENDURA Module Details • Initialization module • Sets up Bit-timing register and BRP registers • Initializes CAN engine • Register module • Registers for a msg Id with Msg Obj • Only registered packets will be received • Also have option of Rx-ing all packets • Unregister module • Dynamically disassociate a node from receiving packets • Converse of Register module

30. ENDURA Module Details • Send Packet module • Sends packet with given message identifier • packets of Type A (11-bit) or Type B (29 bit) • Variable payload from 0 – 8 bytes can be sent • Receive Packet module • Works in conjunction with Register module • Messages stored in Msg. Object after acceptance filtering • Either sent to higher layers through Queue or Stored in Software Buffers

31. ENDURA Module Details • Interrupt Service Routine module • Services the RX_OK interrupt from CAN controller • Identifies the Msg. Obj. with new data • Stores in Software buffer • Translation Module • Translates a CAN 2.0A type to CAN 2.0B type • Translates a CAN 2.0B type to CAN 2.0A type • Care not to disturb CAN 2.0A type Msg. Ids

32. ENDURA Module Interaction

33. ENDURA Translation Module

34. ENDURA Validation • ENDURA layer subjected to following tests: • CAN Conformance test • Performance Tests • Bandwidth Tests • Latency Tests • Endurance Tests • Sporadic packet Tests

35. ENDURA Performance Data • CAN Conformance test • All modules met the CAN protocol conformance • Performance Tests • Performance Tests • Endurance Test • No dropped packets at 10ms delay in packets • Pkts sent = 14,406,543 Pkts dropped = 0 • Sporadic Packet Tests • No packets dropped till packet rate of 10ms • Packets sent at 1000ms, 500ms, 100ms, 50ms, 10ms rate

36. ENDURA Performance Data • Performance Tests • Bandwidth Tests • Maximum Bandwidth measured with IDEAnix = 100 KBPS • Bottleneck due to OS context switching time • Latency in sending a packet through the CAN controller • Latency Tests • RX packet latency in ENDURA layer = 110 μSecs • RX packet latency in CAN application = 856 μSecs • TX packet latency in ENDURA layer = 924 μSecs • TX packet latency in CAN application = 9 mSeconds • Time taken by C_CAN processor to TX a pkt = 110 μSecs • Max Bandwidth that can be realized = 120 KBits/Sec

37. Bandwidth Test Data Packet Rate Vs Packets Rxd Packet Rate Vs Packets Drpd

38. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

39. Outline • Thesis Motivation and background • Objective and Problem statement • Embedded Network background • CAN Background • CAN Applications • CAN Hardware Overview • CAN Protocol Overview • ENDURA design • ENDURA Validation • Future enhancements • ENDURA Benefits • Conclusion

40. Future Enhancement • CAN Bandwidth can be improved • By improving the OS Time Tick from 10 ms • By varying the No. of OS ticks per sec from 100 • CAN Send Packet Latency can be improved • By routing the inter-module packets through the ENDURA layer instead of IDEAnix • This improves latency by 10 times • Implement CAN Gateway nodes capable of communicating to other embedded networks • CAN to Wireless Network gateway (for extending CAN network) • For forming Ad-hoc networks

41. ENDURA Benefits • Modularity of Reconfigurable architectures • Reusability of modules and dynamic addition of functionalities • Reduction of system complexity • Modules can be developed independently • Modules can be tested independently and integrated • Reduction in System design errors

42. Conclusion • Provides a fault-tolerant platform for communication between nodes • Generic implementation that can be swapped with other network implementations • Provides an infrastructure for reconfigurable architecture to perform dynamic reconfiguration • Realization of soft real-time distributed system made possible

43. ?

44. Thank you!

45. Fin!