CAN Based Protocols in Avionics MustRead

DASC - Colorado Springs 2014

CAN Based Protocols in Avionics

2

Agenda

> Introduction

ARINC 825

ARINC 812A

CANOpen

Motivation for CAN FD

What is CAN FD?

CAN FD Use Cases

CAN FD Summary

Summary

CAN FD Additional References

3

Introduction

CAN Bus Basics

Introduced by Bosch in the 1980s, first installed in Mercedes Benz cars

Cost effective

Robust, even in harsh environments

Long term availability

Weight saving over non-networked implementations

Built-in message priority scheme

Built-in error recovery mechanism

For Aerospace Applications

Certain aspects of CAN technology still need to be adapted to airborne equipment

ARINC 825 standards

4

Introduction

Current CAN Bus Application Areas: First application on A318 and A340 for cabin ventilation system control

2005 : A380 => 75 CAN buses, 420 CAN nodes

2009 : A400M => max. 118 buses depending on A/C configuration

2013 : A350 => more than 100 buses

A380 Example: Reduction from 90 single wires to a single 2 wire CAN bus for flight deck control panels

CAN bus is used for environmental control system, fire detection, door controller, water & waste, oxygen systems, galley, seat actuation, cargo loading systems,…

CANopen is used for space applications (ESA programs)

5

Agenda

Introduction

> ARINC 825

ARINC 812A

CANOpen


What is CAN FD?

CAN FD Use Cases

CAN FD Summary

Summary


6

ARINC 825

Motivation for ARINC 825:

The ARINC 825 standard was driven by Airbus and Boeing and defines a communication standard for airborne systems using CAN

Developed by the CAN Technical Working Group of the Airlines Electronic Engineering Committee (AEEC)

Members included Airbus, Boeing, Rockwell Collins, GE Aviation, Vector Informatik

Design Targets:

CAN may function as either a primary or ancillary network

CAN may be integrated into a larger networked architecture to ensure:

Local CAN networks are easily connected to the aircraft network

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ARINC 825

Design Targets:

Provide maxium interoberability and interchangeability of CAN connected LRUs (Line Replaceable Unit)

Maintain configuration flexibility: easy addition, deletion and modification of bus nodes

Simplify interconnection of systems Traffic can easily cross systems and network boundaries

Integrated error detection and error signaling

System level functions such as on-board data load may be implemented

Maintain low cost

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ARINC 825

Scope of ARINC 825:

Characterizes access and data flow relative to CAN and certain aspects of data flow across network boundaries

General concept description Role of CAN in aircraft communication

Network domain characteristics, protocol architecture and bus topology

Data flow across domains

Physical Layer Standard: Electromagnetic protection requirements

Transceiver requirements

Controller requirements (Bus Speed, Bit timing, Bit Encoding/Decoding)

Cabling, connectors and installation

Data Link Layer ISO compliance with CAN2.0B, 29 bits extended identifier standard

Error handling

Bus Arbitration

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ARINC 825

Scope of ARINC 825: CAN Communication

Protocol concept: anyone-to-many and peer-to-peer communication

CAN identifier usage: logical communication channel definition

Interoperability: Data Formats, axis definitions and sign convention

Periodic Health Status: Health Status Message Identifier, Data payload content

Node Service Interface: Concept, Test and Maintenance Support

Bandwidth Management: Bus load calculation

CAN Gateways between other Networks Gateway model specifications

Protocol conversion

Bandwidth management

Data buffering and fault isolation

General Design Guidelines

Recommendations/considerations to avoid network design issues

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ARINC 825

Example: LCC - Logical Communication Channel

Logical Communication Channels provide independent layers of communication

The value of the LCC bits has the highest impact on message prioritization. Channels are arranged according to their overall system importance.

31 24 23 16 15 8 7 0

29 bit CAN Identifier LCC

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ARINC 812A

Motivation for ARINC 812A: Aircraft galley insert equipment has historically been developed without any uniform and concise industry guidance.

Galley inserts designed with unique and non-interchangeable interfaces between functionally similar catering equipment.

Created tremendous inflexibility in galley configurations

Ability to upgrade/retrofit in-flight meal service components reduced

Restricting airlines‘ ability to openly select products between suppliers

Driving up industry costs.

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ARINC 812A

Design Targets:

Functionality for the Master Galley Control Unit (MGCU)

Data Transfer (data up/download)

Network Monitoring

Remote Operation (start/stop catering process, change state, flight information..)

Power Control

Failure monitoring (diagnosis)

Galley inserts (GAIN) shall have at least the following functionalities:

GAIN with Data Transfer

GAIN with Network Monitoring

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ARINC 812A

MGCU-GAIN architecture: • MGCU present on galley

bus • Each GAIN functionality is

controlled and monitored by MCGU

GAIN-GAIN architecture: • Decentralized power

control • MGCU not present on the

galley data bus

GAIN Architectures

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ARINC 812A

Scope of ARINC 812A: Definition of CAN communication for standard data interfaces for Galley Inserts Equipment

E.g.: beverage maker, oven, refrigerator, trash compactor

Related documents:

ARINC 810 for definition of physical interfaces

ISO 11898: Interchange of digital information – CAN for high speed communication

ISO 11898-1: CAN

ISO 11898-2: High Speed Transceiver

ISO 16845: CAN, Conformance Test plan

ARINC 825 for definition of: Physical and transfer layer

Bit and Byte order

Data transfer protocol

CAN-identifier usage

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15

Agenda

Introduction

ARINC 825

ARINC 812A

> CANOpen


What is CAN FD?

CAN FD Use Cases

CAN FD Summary

Summary


16 16

device fromvendor B

device fromvendor C

device fromvendor A

CAN

messageutilization

CAN

messageutilization

CAN

messageutilization

CANOpen

Usage of CAN according to manufacturer specific rules:

pin assignment on CAN adaptors

bit rate

different meaning of messages with the same CAN identifier

different communication concepts

System Integrator’s problem:

17 17

CANOpen

device fromvendor B

device fromvendor C

device fromvendor A

CAN

messageutilization

CAN

messageutilization

CAN

messageutilization

Standardizing

bus physics

meaning of messages

communications model

Makes it much easier to setup and integrate networks.

Easier Integration through Standardization:

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CANOpen

functionality of device classes

usage of messages

configuration interface

network management

error handling

electrical interface, bit rates, connectors

DeviceProfile A

CAN

DeviceProfile B

DeviceProfile C

ISO/OSI Layer 7: Application - CANopenCommunication Profile

ISO/OSI Layer 2: Data Link

ISO/OSI Layer 1: Physical

Defined by CANopen standard:

What is defined by CANOpen?

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Applications:

Aircraft systems

Systems development activities

Integration of COTS devices

Test systems

Space systems

ESA - EXOMARS (Entry Descent & Landing and Rover Modules)

ESEO – European Student Earth Orbiter

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CANOpen

20

Agenda

Introduction

ARINC 825

ARINC 812A

CANOpen

> Motivation for CAN FD

What is CAN FD?

CAN FD Use Cases

CAN FD Summary

Summary


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Why?

The ever increasing electrification of previous mechanically controlled systems, as well as, new electrical features drive the need for higher data throughput.

More LRUs

More nodes

More networks

More data

But at what cost?

Engineering effort

Financial

Physical dimensions (weight & size)


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CAN networks reached practical maximum of data transfer

Many CAN buses have reached 50%-95%+ bus load level

CAN messages contain

At most, only ~40-50% of the bandwidth is used to exchange useful data

Current CAN bus speeds 1Mbit/s Limited by physical characteristics of the wiring

Most networks at 500Kbit/s or less

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CAN bus speed is limited by the In-Frame Response mechanism

ACK generation delay in CAN controller +

Propagation delay through the transceiver +

Propagation delay over wire

Other protocols have much higher data throughput rate

Ethernet UDP – ~64K bytes/datagram, 64 bytes overhead (IPV4)

FlexRay – 254 bytes/frame, 8 bytes of overhead

CAN_H

CAN_L

CAN-ECU

RT

CAN-ECU

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Agenda

Introduction

ARINC 825

ARINC 812A

CANOpen


> What is CAN FD?

CAN FD Use Cases

CAN FD Summary

Summary


25

What is CAN FD?

CAN FD is an improved CAN protocol

CAN FD is a serial communications protocol based on CAN 2.0

Two new features added:

Support dual bit rates within a message Arbitration-Phase – same bit rate as standard CAN

Data-Phase – bit rates higher 1 Mbit/s are possible (up to ~5 Mbit/s)

Support larger data lengths than “classic” CAN Up to 64 bytes/message

System cost similar to standard CAN

Smooth migration at reasonable cost

Classic CAN and CAN FD LRUs can be mixed under certain conditions

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What is CAN FD?

CAN FD Oscilloscope Trace

Arbitration

Phase

Data

Phase Arbitration

Phase

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What is CAN FD?

Combining CAN and CAN-FD:

Scenario 1

Mix of classic CAN and CAN FD nodes:

Communicate only with classic CAN messages

Switch off the classic CAN nodes and only interact with CAN FD nodes (e.g. during flashing)

Scenario 2

All nodes are CAN FD capable:

Classic and FD messages can be mixed

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CAN FD Use Cases

Use cases for CAN FD:

Reduce bus loading on an existing bus

Avoid splitting networks

Avoid splitting data into multiple frames

Increase # of LRUs on the bus

Communicate with high data volume LRUs

Accelerate communication on long bus lines

Faster software loading within aircraft

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CAN FD Summary

Serial communication networks require increased bandwidth

Due to high bus load levels

For program loading applications

CAN FD can provide significantly increased bandwidth

Due to increased data clock rates

Due to larger data payloads

CAN FD is an improvement of well known CAN technology

Event triggered system

Consistent arbitration and acknowledge mechanism

30

Agenda

Introduction

ARINC 825

ARINC 812A

CANOpen


What is CAN FD?

CAN FD Use Cases

CAN FD Summary

> Summary


31

Summary

CAN increasing use in aerospace applications

ARINC 825 – standardized CAN for airborne use

ARINC 812A – standardized CAN for galley insert (GAIN) equipment

CANOpen has found application in aerospace systems

Satellite sensors (ESA)

Integration of COTS components

CAN-FD “next-gen” CAN solution for high data rate applications

Lower overhead

Higher data throughput

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Thank you for your attention.

For detailed information about Vector and our products please visit

www.vector.com

Author:

Arne Brehmer Vector Informatik GmbH

Vector Cantech, Inc. Rick Lotoczky

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Paper “CAN with Flexible Data Rate” – Florian Hartwich, Robert Bosch GmbH;CAN in Automation, iCC 2012, March 2012

Presentation “CAN FD CAN with Flexible Data Rate” – Florian Hartwich, Robert Bosch, GmbH; Feb. 15, 2012

CAN with Flexible Data Rate – Specification Version 1.0 (Released April 17, 2012), Robert Bosch, GmbH; April, 2012

http://www.bosch-semiconductors.de/en/ubk_semiconductors/safe/ip_modules/can_fd/can.html

M_CAN Controller Area Network User’s Manual, Revision 2.0.1, Robert Bosch, GmbH; March 12, 2012

CAN Based Protocols in Avionics MustRead

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