Listen to your hosts Dave Jones & Chris Gammell talk about electronics design and the electronics industry in general. If you have any interest in electronics at all, from hobbyist/hacker/maker to engineering professional you'll find something of interest here.
Ken heard episode #631 where Chris was talking about a Noisy Rude Bus and he objected. Stringently (it seems Ken has since pulled down the posts, but they were in good fun)
Chris had been planning to talk about Ken’s recent awesome post about CAN hacking and cars being stolen, so he asked Ken to be on the show!
CAN was invented to reduce weight in car cable harnesses, which were increasing rapidly with more electrical features being included.
CAN vs LIN
CAN was expensive, but LIN is cheap because it’s bit banging the protocol from a microcontroller
There are bridges to go between CAN and LIN buses.
Modern cars have 20-100 ECUs (controllers), but it depends on the features the car has. But that’s not just microcontrollers, Ken estimates that could be as high as 700.
Chris and Ken both had dealth with Philips / Freescale / NXP / Motorola as silicon vendors in the automotive space
How does a tiny microcontroller get data onto the bus?
Prioritized traffic
CAN indentifier field has priority baked in
Bus works like a giant AND gate where the lowest address wins
11 bits
How to unwind CAN traffic
Packing signals into CAN frame
Tools to reverse engineer
Protocol decoder for sigrok
CAN HG
250kb is slow
CAN bus bandwidth
There is Ethernet in cars now, especially with more and more cameras
Bandwidth vs latency
Addressing through a gateway
Atomic broadcasts means you know that each device has processed it
Protocol hacking
Trucks aren’t OEM based so more vertically integrated
SAE J1939 standard in trucks
If say Toyota develops the CAN messages, DBC files decode everything.
But manufacturers don’t publish them, so some car messages are reverse engineered
Accessories bus
Who has access to DBCs?
Diagnostic systems
OBD2
CARB
CAN is physical ISO 11898
CAN XL has IP packets, so you can use wireshark
Ken has written about wireshark
CAN 2.0, CAN FD
Devices on a bus are normally all bare metal or RTOS because of the timing requirements
OSEK standard
Embedded system abstraction
Dealing with the magnitude of decisions making in the automotive industry
Chris asked about whether self-driving will happen in 5 or 20 years? (ie. does he agree with Chris or Dave). It was the latter, sadly.