Embedded Systems Academy

The 15th international CAN Conference took place in Vienna on October 27th and 28th 2015. On two days, a total of 23 papers were presented. Topics included current application examples, security and IoT (Internet of Things)  issues and “everything” CAN FD (Flexible Data Rate) related. CAN FD with its increased data rate was the major topic of this conference, many papers were directly related to it.

As CAN FD is not backward compatible to CAN, one of the session topics was migration from CAN to CAN FD. Mixing CAN and CAN FD controllers is only possible if the CAN FD messages are hidden from the CAN controllers as they would generate error frames upon reception. One approach is using partial networking transceivers where traditional CAN controllers are put to sleep during CAN FD communication. After seeing a specific sleep message, transceivers for partial networking can keep the connected CAN controller in sleep mode until a specific wake up message is received – no other message on the network causes a wake-up.

NXP presented a paper about their “FD Shield” transceiver. This transceiver is used to connect legacy CAN controllers to a CAN FD network. The CAN FD traffic is somewhat “shielded” from the CAN controller, only regular CAN traffic passes through but CAN FD messages are blocked as soon as they can be detected. However, there is a side effect: Each CAN FD frame on the network causes a local, not propagated receive error at the CAN controller side. As a result the CAN controller may go error passive. However, as transmits works fine, it will not go bus off and can still be used. Although not perfect, this is a quick and easy solution during a migration phase from CAN to CAN FD.

Another way to quickly connect to CAN FD networks is using Microchips external CAN FD controller using an SPI connection to the host controller. Here designers need to carefully choose the clock rate used on the serial interface side; depending on the CAN FD data rate used the SPI clock might need to be 10 or even 16Mhz. If a CAN FD data rate of 8Mbps is used, then a 10Mhz clock rate on the SPI side is sufficient to handle 100% bus load. However, the host controller of course needs to be able to handle the 10Mhz SPI traffic, too.

Other papers showed how CAN FD can be used in Linux systems, AUTOSAR and J1939, In general, the physical layout for CAN FD networks is not as flexible as it is with regular CAN. With faster bit rates ringing and reflections become more of a problem as they used to be. As usual, if an application tries to get close to the physical limits that a technology provides, more care must be taken when determining the physical layout and terminations.

With more and more CAN networks also getting some “remote access” option or even a gateway/firewall to the Internet, security of CAN networks suddenly becomes more important. In the past, CAN networks could be regarded as “closed” (inside a machinery, no remote access) so no precautions were taken in regards to security. Once a CAN network goes “online”, even if it is by the means of some firewall and even if it is only part-time, the entire security concept needs to be re-evaluated. Recent car hacks have shown that once hackers are past the firewall, they can do “anything” because there is no security layer in the CAN network.

Papers from Robert Bosch GmbH and the CiA showed some possible options to add encryption also to CAN communication, however, that directly has an impact on debugging and testing. If communication between two ECUs is secure, how do we monitor or debug it? So the debugger/tester/logger needs to part of this equation, too. It will be interesting to see where this goes, will at some point security be added to all CAN communication or will it be limit to “relevant” transmissions like commands that actually do something to the system?

Once the papers are added to the CiA’s server system, they will be available for download.

With about 900 exhibitors the Embedded World reached a size where it is impossible to “see it all”. Yes, you can still walk by all booths in a day, but you might easily miss hidden highlights. It was quite obvious that IoT – the Internet of Things – is a current hype. To me this is quite astonishing as already some 10+ years ago we built an “Embedded Internet Demo” – at that time based on a Philips 8051 with a dial-up modem connected. The main difference between now and then is that now smart phones are widely spread and we are “always online” and now can access our embedded devices “at any time”. Among the visitors one could recognize a lot of skepticism for what exactly we really need the IoT, other then it being hip and cool to be able to control “everything” with our smart phone.

An unusual approach to get remote access to embedded applications was shown by Raisonance (http://www.iotize.com) – they have a miniature NFC or Bluetooth module that connect to the JTAG/SWD debug port of an application. So it can be added to any application with debug port, sometimes even without the need to re-compile the code, if you have the knowledge where in memory the variables are that you want to have remote access to. A great tool to get started with IoT without requiring a re-design of existing hardware.

At the CiA (CAN in Automation) booth a CAN FD demo integrated devices and tools from multiple vendors. CAN FD (Flexible Data) allows higher bit rates and longer contents (up to 64 bytes) of the data frame. Especially bootloader applications and other software update features benefit from the higher data throughput. For such applications it seems to be possible to increase the effective data throughout 8 fold easily, potentially even more.

We at ESAcademy further enhanced our portfolio of CANopen Diag products. There is now a second hardware, based on PEAK’s mini Display, that offers a subset of the diagnostic features provided at a price point of well below 1000 Euro. The CANopen Test Machine System part of the CANopen Diag now allows to create tests based on MS Visio graphs. The transitions in a state diagram can be used to transmit or receive a CAN/CANopen message or to influence/set/test/query variables or timers. More details and examples will be published shortly.

This year the Embedded World (www.embedded-world.de) in Nuremberg expects 30k+ vistors from 35+ countries. Show days are from 24th to 26th of February. For companies “into CAN” one of the hot topics is CAN FD – more and more products (microcontrollers as well as interfaces) are now available supporting the new standard supporting higher data rates. You can see the Bosch CAN FD demonstrator at the CiA booth (booth 608 in hall 1). This demo includes our CANopen Magic software connected to a CAN FD bus using the latest PEAK CAN interface. If you have questions and would like to meet us, come over to our partner PEAK System (booth 606, hall 1, just next to the CiA booth). Looking forward to seeing you!

On March 5th, ESAcademy will conduct the following classes at the iCC together with NXP Semiconductors:

08:30 to 09:30 Everything CAN and NXP CAN Controller Intro
A 30 year old technology, here to stay for another 30 years

An overview of the almost 30 year old CAN technology, where it came from and where it goes. CAN is used in many new electronic designs, also thanks to continuous advancements in CAN controller technology. Comparison of various CAN controller technologies.

09:45 to 10:30 CANopen Essence
New to CANopen? Learn the key features in just 45 Minutes

With its 4000+ pages the CANopen drafts and standards are overwhelming to newcomers. Join this class to get an overview of the common technical key features that make CANopen work.

11:30 to 13:00  Introduction to NXP CAN microcontrollers and Co-Processors
CAN controllers, CANopen Co-Processor, J1939 Co-Processor

Specialties of NXP CAN controllers and how an LPC11C24 can be used as a communication Co-Processor. Using the LPC11C24 with integrated CAN transceivers to implement a Co-Processor to implement and handle a higher-layer protocol, offloading this task from a host processor system. The host system communicates with the gateway via
UART, I2C or SPI.

Participants may qualify for a free NXP Evaluation Kit (must be present to qualify, 50 kits available).

For more information about the international CAN conference visit: www.can-cia.org

For many years the maximum bit rate of CAN (Controller Area Network) has been 1Mbps. Not only was it a maximum for the bit rate, it also resulted in a “touchy” physical layout: cable length restrictions were as low as 30m.

The limits of speed vs. cable length comes from the requirement, that in CAN a bit needs to be stable on the entire bus, before the next bit may start. Some bits can be over-written, a feature which is used for arbitration, acknowledgments and error handling.

Bosch, the inventor of CAN, now introduced a white paper “CAN with Flexible Data-Rate” showing how a higher data rate can be achieved. The main suggested feature here is to allow switching between a low (backward compatible) bit rate and a much higher bit rate within a single message.

In short, a single CAN message consist of control data at the beginning and the end of a message with the data field “in the middle”. The core idea is to use the lower bit rate for the control data and the higher bit rate for the data field only. In addition the maximum data field size is increased from previously 8 bytes to now 64 bytes.

If the higher bit rate is 8 times higher than that of the base rate it would be possible to achieve an 8 times higher data-throughput WITHOUT changing the real-time behavior.

For more info, see the white paper at:
www.semiconductors.bosch.de/media/pdf/canliteratur/can_fd.pdf