Features of CiA 447 Application profile for special-purpose car add-on devices

Transcription

1 Features of CiA 447 Application profile for special-purpose car add-on devices Olaf Pfeiffer, Embedded Systems Academy GmbH The trend to add more distributed electronics to applications also applies to taxis, emergency response vehicles, governmental vehicles and cars with special controls for handicapped drivers. However, in modern cars it becomes more and more difficult to add electronics, as build-in electronics and airbags are a closed system and all space around the dashboard is occupied. Access to the internal vehicle networks (IVN) is a delicate matter. For safety reasons, the car manufacturers are reluctant to allow direct access to "everyone". CiA447 defines an open vehicle network with which car manufacturers provide limited access to their internal networks. As all accesses go through a gateway, the gateway can limit the access to those parameters considered "safe". As an example, where supported, buttons and displays of the car can be used by CiA 447 devices. However, the ultimate control remains within the car. In an emergency situation, the car could still override / overwrite the display with required warnings. To allow easy and simple network connections, a standard connector, extended plugand-play mechanisms as well as power-down and wake-up controls are defined. Overview of the functionality provided by CiA 447 On the physical side, CiA 447 specifies to use ISO The CiA 447 devices use an 18-pin VDA interface connector that provides up to 4A power and access to the CAN_L and CAN_H lines. An optional 2-pin 16A power connector is defined for devices requiring more than 4A. Other optional signals include things like ignition (KL15), speed pulse signal, PTT Push-To-Talk signal and audio signals. The CAN bit rate is set to 125 kbit/s. Figure 1: 18-pin VDA interface connector On the logical side, a CiA447 network is limited up to 16 nodes (versus up to 127 in CiA301 CANopen) allowing for a full SDO mesh implementation with one SDO channel from every node to every node. This requires a custom pre-defined connection set, the CAN message identifiers used for these SDO channels are different from the CiA 301 default. As a result, regular CiA 301 devices such as generic I/O modules do not work in a CiA 447 network, all nodes in a CiA 447 network must be CiA 447 compliant. The node 1 (one) is reserved for and must be used by the gateway. A gateway is mandatory for a CiA447 system to operate, as it is responsible for the network management including detecting and starting nodes. Typically the gateway is provided by the car manufacturer, however, there are also generic gateway solutions that connect to the OBD-II interface of a car to allow the connection of CiA447 compatible devices. In comparison to "regular" CiA301 CANopen, CiA447 has a few functions, protocols and techniques to satisfy the specific application requirements: a high level of plug-and-play functionality 4-11

2 numerous virtual devices (in V2.0 up to 128) signals contain status information direct SDO communication between all nodes sharing and locking of limited resources, like displays In the following paragraphs these features are explained. High level of plug-and-play functionality One of the early requests for the Taxi application was, that it must be possible to quickly exchange components. Drivers need to be able to do this (like replacing a printer) without requiring the help of a specially trained technician. This functionality was provided by enhancing the LSS (Layer Setting Services) protocols of CiA305 with the "Fast Scan" protocol. The enhancements allow scanning for unconfigured nodes based on their LSS- (128bit device from Object Dictionary entry 1018h). Detecting a single node and assigning it a node takes less than two seconds using the Fast Scan protocol. The plug-and-play support in CiA447 is the gateway's responsibility. It detects nodes, assigns node s and monitors heartbeat messages to do so. A known limitation of the plug-and-play support comes from devices with a fixed node, which in general are allowed in CiA447. If devices with fixed node s are used, the person doing the "plugging" is responsible for ensuring that no other device on the network is currently using a node that is already present on the network. True plug-and-play is therefore only available for those devices supporting the LSS Fast Scan protocols. Extensive use of Virtual s The concept of using Virtual s is essential to CiA447. Initially only up to 32 virtual devices were supported. Since V2.0 of CiA 447 the number of bits used to define virtual devices was extended to support up to 128. These are located in the Object Dictionary at index 6000h at the subindexes one to four. These entries are one of the first read by communication partners, to determine which node implements what and which resources are available where. As an example, a roof bar controller would check which nodes implement roof bars and from then on focus on the communication with that device, ignoring others. Virtual device IVN gateway class 0 IVN gateway class 1 IVN gateway class 2 IVN gateway class 3 Fire extinguishing system Emergency fresh-air system Power supply Discrete inputs Terminal GPS Navigation system Taximeter Printer Real time clock (RTC) Driver identification Tariff display Taxi alarm system Radio Audio switch Roof bar light Roof bar sound Blue light flasher module Roof bar controller Radio controller Handicap controller Radio hand-free conversation Tester/tool Information signaler Video Data recorder Switch keypad Input output switch Engine control Active speed control Figure 2: list of virtual devices Type Tester Generic device Generic device 4-12

3 Signals contain status information In CiA447 signals that normally only have a binary on and off state use two bits to represent a total of four states: 00 off 01 on 10 failure 11 signal not available As a result, consumers of such signals can directly determine if the signal is valid without requiring an extra parameter or mechanism. A similar setup has been implemented for analog values. In an analog value, all bits set stand for "signal not available" and all bits set minus one for "failure". For example, object 605Ah defines the displayed vehicle speed using a 16bit value. The value range is from 0 to 0FFEh representing 0.1 local distance unit per hour. Values 0FFFh to FFFDh are reserved, FFFEh stands for failure and FFFFh for signal not available. Direct node-to-node SDO communication: SDO mesh In CiA447 each node has 15 or 16 SDO server and 15 SDO clients, allowing each node to send direct SDO requests to any other node. This allows CiA447 devices to independently scan the network for communication partners and get direct access to all their Object Dictionary, not limited to data that is mapped into PDOs. For the pre-defined connection set (how CAN message identifiers are used for SDOs and PDOs) this means that 480 CAN identifiers (of 2048 available) are used to provide these communication channels. Table 1 and 2 of CiA447-4 show which CAN identifiers are used. C1-241 h 242 h 243 h 244 h 245 h 246 h 247 h 248 h 249 h 24A h 24B h 24C h 24D h 24E h 24F h C2 250 h h 253 h 254 h 255 h 256 h 257 h 258 h 259 h 25A h 25B h 25C h 25D h 25E h 25F h C3 260 h 261 h h 264 h 265 h 266 h 267 h 268 h 269 h 26A h 26B h 26C h 26D h 26E h 26F h C4 270 h 271 h 272 h h 275 h 276 h 277 h 278 h 279 h 27A h 27B h 27C h 27D h 27E h 27F h C5 340 h 341 h 342 h 343 h h 346 h 347 h 348 h 349 h 34A h 34B h 34C h 34D h 34E h 34F h C6 350 h 351 h 352 h 353 h 354 h h 357 h 358 h 359 h 35A h 35B h 35C h 35D h 35E h 35F h C7 360 h 361 h 362 h 363 h 364 h 365 h h 368 h 369 h 36A h 36B h 36C h 36D h 36E h 36F h C8 370 h 371 h 372 h 373 h 374 h 375 h 376 h h 379 h 37A h 37B h 37C h 37D h 37E h 37F h C9 440 h 441 h 442 h 443 h 444 h 445 h 446 h 447 h h 44A h 44B h 44C h 44D h 44E h 44F h C h 451 h 452 h 453 h 454 h 455 h 456 h 457 h 458 h - 45A h 45B h 45C h 45D h 45E h 45F h C h 461 h 462 h 463 h 464 h 465 h 466 h 467 h 468 h 469 h - 46B h 46C h 46D h 46E h 46F h C h 471 h 472 h 473 h 474 h 475 h 476 h 477 h 478 h 479 h 47A h - 47C h 47D h 47E h 47F h C h 541 h 542 h 543 h 544 h 545 h 546 h 547 h 548 h 549 h 54A h 54B h - 54D h 54E h 54F h C h 551 h 552 h 553 h 554 h 555 h 556 h 557 h 558 h 559 h 55A h 55B h 55C h - 55E h 55F h C h 561 h 562 h 563 h 564 h 565 h 566 h 567 h 568 h 569 h 56A h 56B h 56C h 56D h - 56F h C h 571 h 572 h 573 h 574 h 575 h 576 h 577 h 578 h 579 h 57A h 57B h 57C h 57D h 57E h - Table 1 SDO CAN-s for request client to server (S) C1-1C1 h 1C2 h 1C3 h 1C4 h 1C5 h 1C6 h 1C7 h 1C8 h 1C9 h 1CA h 1CB h 1CC h 1CD h 1CE h 1CF h C2 1D0 h - 1D2 h 1D3 h 1D4 h 1D5 h 1D6 h 1D7 h 1D8 h 1D9 h 1DA h 1DB h 1DC h 1DD h 1DE h 1DF h 4-13

4 C3 1E0 h 1E1 h - 1E3 h 1E4 h 1E5 h 1E6 h 1E7 h 1E8 h 1E9 h 1EA h 1EB h 1EC h 1ED h 1EE h 1EF h C4 1F0 h 1F1 h 1F2 h - 1F4 h 1F5 h 1F6 h 1F7 h 1F8 h 1F9 h 1FA h 1FB h 1FC h 1FD h 1FE h 1FF h C5 2C0 h 2C1 h 2C2 h 2C3 h - 2C5 h 2C6 h 2C7 h 2C8 h 2C9 h 2CA h 2CB h 2CC h 2CD h 2CE h 2CF h C6 2D0 h 2D1 h 2D2 h 2D3 h 2D4 h - 2D6 h 2D7 h 2D8 h 2D9 h 2DA h 2DB h 2DC h 2DD h 2DE h 2DF h C7 2E0 h 2E1 h 2E2 h 2E3 h 2E4 h 2E5 h - 2E7 h 2E8 h 2E9 h 2EA h 2EB h 2EC h 2ED h 2EE h 2EF h C8 2F0 h 2F1 h 2F2 h 2F3 h 2F4 h 2F5 h 2F6 h - 2F8 h 2F9 h 2FA h 2FB h 2FC h 2FD h 2FE h 2FF h C9 3C0 h 3C1 h 3C2 h 3C3 h 3C4 h 3C5 h 3C6 h 3C7 h - 3C9 h 3CA h 3CB h 3CC h 3CD h 3CE h 3CF h C10 3D0 h 3D1 h 3D2 h 3D3 h 3D4 h 3D5 h 3D6 h 3D7 h 3D8 h - 3DA h 3DB h 3DC h 3DD h 3DE h 3DF h C11 3E0 h 3E1 h 3E2 h 3E3 h 3E4 h 3E5 h 3E6 h 3E7 h 3E8 h 3E9 h - 3EB h 3EC h 3ED h 3EE h 3EF h C12 3F0 h 3F1 h 3F2 h 3F3 h 3F4 h 3F5 h 3F6 h 3F7 h 3F8 h 3F9 h 3FA h - 3FC h 3FD h 3FE h 3FF h C13 4C0 h 4C1 h 4C2 h 4C3 h 4C4 h 4C5 h 4C6 h 4C7 h 4C8 h 4C9 h 4CA h 4CB h - 4CD h 4CE h 4CF h C14 4D0 h 4D1 h 4D2 h 4D3 h 4D4 h 4D5 h 4D6 h 4D7 h 4D8 h 4D9 h 4DA h 4DB h 4DC h - 4DE h 4DF h C15 4E0 h 4E1 h 4E2 h 4E3 h 4E4 h 4E5 h 4E6 h 4E7 h 4E8 h 4E9 h 4EA h 4EB h 4EC h 4ED h - 4EF h C16 4F0 h 4F1 h 4F2 h 4F3 h 4F4 h 4F5 h 4F6 h 4F7 h 4F8 h 4F9 h 4FA h 4FB h 4FC h 4FD h 4FE h - Table 2 SDO CAN-s for response server (S) to client (C) Resource sharing CiA447 allows sharing a car's resources, such as a dashboard display. In order to provide controlled access, a locking mechanism with confirmation is required to manage the access to such shared resources. The locking and release mechanism for the "Display 1" is used as an example here to demonstrate how the locking mechanism works. Object 6098h is an 8bit command for Display 1. For simplicity in this example, Display 1 access is provided by the gateway (node 1). Using an SDO write request, any CiA447 node can now write a command to the display control. Writing a value of 1 requests a lock (device wants to access display), writing a value of 2 requests the release of a previously granted lock. After writing a lock request, the device needs to read the display status. Object 6097h is an 8bit status value for Display 1. Using an SDO read request, any CiA447 node can read 6097h to determine the display status. A value of 2 to 17 means that it is currently locked to node 1 to 16. So by reading back the status, a node requesting a lock can check if a written lock request was successful. Once a lock is established, the node "owning" the lock can use the resource, in this case writing to the display. Such locking mechanisms have been defined for all displays and buttons. Note that it is the responsibility of the resource manager to determine potential priorities, including canceling locks. A dashboard controller will prioritize messages from the car over any other CiA447 request. If an internal warning needs to be displayed, an established lock may be canceled. Olaf Pfeiffer Embedded Systems Academy Bahnhofstr Barsinghausen Tel: Fax: opfeiffer@esacademy.com

5 Appendix Selection of gateway signals defined by CiA447 The following is a summary of some of the signals defined for gateways. Most of them are optional, so it is up to the individual car/gateway manufacturer to decide if they want to provide this signal or not. PDO Data that transmits periodically (typically every 100 ms) or on change-of state ignition, flaps (doors and hatches), illumination level and car lights, wiper system, central locking system, belt buckles, turn indicator, seat adjustments, accident detection, horn, anti-theft system Car power train engine and wheel data Steering wheel and dashboard inputs steering wheel, dashboard and console switches H user terminal user terminal (display/switches), function and control keys GPS position latitude and longitude Status of add-on devices SDO Data that needs to be requested VIN (vehicle identification number), steering wheel angle, temperatures and climate control Car power train odometer, displayed speed, tank, fuel consumption, gear SDO Commands that may be supported lights and illumination, locking system, windows, doors, hatches, seat adjustment, wiper system, climate control, terminal displays 4-15