An Introduction to the CAN Bus: How to Programmatically Control a Car
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Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#2Interesting - never realized there would be multiple CAN buses in a car. That probably makes it a lot easier to not screw things up - if you know that the medium speed bus is only connected to non-safety-critical systems, then it's easier to trust that when you send out your hand-crafted CAN packets, you're not going to cause anything too drastic to happen.
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#3Does anybody know where the trend is going? Do electric cars have standard buses or are they moving to proprietary (and not published) buses?
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#4Does anybody know where the trend is going? Do electric cars have standard buses or are they moving to proprietary (and not published) buses?
CAN will stay for quite a while, as will LIN. However, higher speed buses (esp. FlexRay and MOST) are very, very slowly being replaced by Automotive Ethernet (which uses a proprietary physical layer, called BroadR-Reach). Where CAN used checksums (additional, application layer checksum in addition to the protocol layer) to prevent tampering (modifying live data), the Ethernet based protocols will use what AUTOSAR calls Secure On-Board communication, which features ECU-to-ECU end to end protection.
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#5Does anybody know where the trend is going? Do electric cars have standard buses or are they moving to proprietary (and not published) buses?
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Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#6Interesting - never realized there would be multiple CAN buses in a car. That probably makes it a lot easier to not screw things up - if you know that the medium speed bus is only connected to non-safety-critical systems, then it's easier to trust that when you send out your hand-crafted CAN packets, you're not going to cause anything too drastic to happen.
You want to keep "unimportant" (think radio) away from "important" (drive train). Also, there are only so many IDs you can use.
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#7Interesting - never realized there would be multiple CAN buses in a car. That probably makes it a lot easier to not screw things up - if you know that the medium speed bus is only connected to non-safety-critical systems, then it's easier to trust that when you send out your hand-crafted CAN packets, you're not going to cause anything too drastic to happen.
Security (or safety) is one reason for multiple CAN buses. Another is saturation of the bus (too many messages).
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#8Does anybody know where the trend is going? Do electric cars have standard buses or are they moving to proprietary (and not published) buses?
CAN will stay for quite a while, as will LIN. However, higher speed buses (esp. FlexRay and MOST) are very, very slowly being replaced by Automotive Ethernet (which uses a proprietary physical layer, called BroadR-Reach). Where CAN used checksums (additional, application layer checksum in addition to the protocol layer) to prevent tampering (modifying live data), the Ethernet based protocols will use what AUTOSAR cal…
Oh interesting. I left the car industry when flexray was the newest bus available and MOST wast only used by Audi (for their backseat screens or some such entertainment systems).
The problem with flexray was that it was supposed to be reliable with redundant cabling, but manufacturers immediately turned around to use redundancy to double the bandwidth.
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#9Love CAN, beautifully simple. Of course the "arbitration id" needs to be unique to an ECU, but each can send multiple different ones - the purpose of the ID is to always send the one with the lowest number. When designing the system, this ID defines the priority of each message - e.g. brake lights are more important than radio volume up :)
Re: An Introduction to the CAN Bus: How to Programmatically Control a Car
#10Can you imagine the havok when terrorists figure out they can program cars to hunt and kill pedestrians in crowded spaces? Currently the terrorist needs to drive the vehicle, which makes it a suicide mission. How much more deadly would it be if it was reduced to just the cost of the car and a low chance of getting caught? How can we defend against this?