CAN bus - wassat?

[The Other PaulG]

So what's CAN bus then?

My net search offered some advice...

The CAN Bus interface uses an asynchronous transmission scheme controlled by start and stop bits at the beginning and end of each character. This interface is used, employing serial binary interchange. Information is passed from transmitters to receivers in a data frame.

...but nothing I could even begin to understand.

Please could any of you extremely bright people describe in laymans terms how a CAN bus system differs from a traditional electrical set-up?

Should get the grey matter stirred up on a Friday afternoon...!

Cheers,

PG

 

[TheWarlock]

Paul,

to put it very simply, it's a computer network.

Imagine you have multiple PCs in an office and you want them all able to talk to each other and other servers (network yeah?). You don't run a wire from each of them to each other and down the corridors to the servers. You plug them into a network connection, simply put, on the wire.

This is how CanBus works. A single wire network. Every electrical item on it acts similar to a PC with an identification code that it attaches to all communications similar to TCP/IP and the bike computer / brain / ECU deciphers it all and supplies current for everything required as and when needed.

That's the theory and also explains why people are so scared of it as we all know how reliable IT networks are. However BMW and Mercedes and some others have been using the technology in their cars for a number of years now quite successfully, so it should work. I hope.

Any minute now there will be other, brighter, folk along to tell me how wrong I am and that I am talking complete bo*&ox. What you gonna do?

 

[TheWarlock]

The other thing to remember with CanBus is that the systems tend not to have fuses as at system start / boot, it does a system check to make sure everything is working correctly. If there is a problem, the system shuts down the affected portion in order to safeguard the rest of the network. This means that if you go interfering with a CanBus system, you can very easily end up in the situation where nothing works beyond the affected or interfered with part.

I know of one example where a person from an agricultural background decided to hook up a trailer with faulty lighting to the trailer lighting socket on a new vehicle. This resulted in all light on the rear of the vehicle failing to work along with the trailer. When the vehicle was returned to the dealers, he conveniently forgot to mention the trailer and simply informed them that the lights had stopped working. It took some time before the dealers eventually got an admission from him as to the course of events. Naturally enough fault codes gave some indication, but as the trailer was external, not enough.

Fun, fun, fun.

 

[The Other PaulG]

Thanks - that's a great description, I can understand that perfectly.

But I could still fix it with my swiss army knife, sitting on the roadside 100km outside Ouarzazate, couldn't I.....?

 

[cookie]

a more difficult question: what benefit is it to me as a rider apart from not having to carry a spare fuse?

 

[TheWarlock]

Paul,

Absolutely Sir. And has Sir considered a Leatherperson Multitool with additional bit set and CanBus resetting tool?

 

[TheWarlock]

a more difficult question: what benefit is it to me as a rider apart from not having to carry a spare fuse?

Simply put, weight saving. It's one of the primary ways they managed to save the 33kg on the 1200 GS over the 1150 GS. Have you ever held the full wiring loom from a motorcycle, never mind a car? They are not light.

 

[avrolancaster]

R1150GS loom 3.125 kg
R1200 loom 2.450 kg

 

[cookie]

why is it lighter?

all components need a live feed to them, as do switches etc. where's the saving on a bike? i realise on a car, there are seperate controller units each end of the car, so they only need a couple of control wires & a live running the length of the car, but a GS12 does not have that or does it?

i suppose the weight of the fusebox is saved. i guess that's the 0.675kg right there.

 

[wessie]

a more difficult question: what benefit is it to me as a rider apart from not having to carry a spare fuse?

It reduces the amount of copper wire in the bike. This not only has weight benefits but is much cheaper to source and assemble.

I was involved in a project that introduced CANbus to the last genreation of analogue photocopiers. We managed to save hundreds of pounds per machine. Mainly by reducing our labour cost.

Making a wiring harness is expensive. Much of the assembly is done by people. Machines are very good at fitting tags and chopping wire to the right length. They are crap at assembling the harness into the right shape.

With CANbus much of the "wiring" is on printed circuit boards or in ribbon cables. These can be made by machines.

Final assembly of these PCBs and ribbon cables is also much cheaper as it reduces man hours considerably.

So, the benefit to you should be a cheaper product. However, I guess with BMW, they will just trouser any extra profit for themselves...

 

[Daffy]

Call me a cynic (if thats how you spell it) but the benefits of CANBus are more to do with forcing you to take your bike to the dealer when it goes wrong, its a fact that once a machine (car, bike truck etc etc) gets to a certain age it will generally be maintained outside of the manufacturers network. CanBus ensures that only your franchised dealer can fix many faults, therefore keeping the dealer wealthy and also ensuring that you don't buy your parts from a factor.

There is legislation that prevents BMW (or anyone else) from witholding info or tools but most manufacturers get around that by putting lots of obstacles in the way.

Dont think the weight or cost savings will benefit you, when did you ever look at a new jacket or your belly and think thats too heavy it might slow me down?

 

[st247]

So what's CAN bus then?

My net search offered some advice...

The CAN Bus interface uses an asynchronous transmission scheme controlled by start and stop bits at the beginning and end of each character. This interface is used, employing serial binary interchange. Information is passed from transmitters to receivers in a data frame.

...but nothing I could even begin to understand.

Please could any of you extremely bright people describe in laymans terms how a CAN bus system differs from a traditional electrical set-up?

Should get the grey matter stirred up on a Friday afternoon...!

Cheers,

PG

There's quite a good description/comparison of the can bus vs standard wiring systems here.

 

[Spout]

There's quite a good description/comparison of the can bus vs standard wiring systems here.

I was trying to find that link to post on this thread. Excellent bit of writing (although I had to read it a few times )

 

[cookie]

It reduces the amount of copper wire in the bike. This not only has weight benefits but is much cheaper to source and assemble.

I was involved in a project that introduced CANbus to the last genreation of analogue photocopiers. We managed to save hundreds of pounds per machine. Mainly by reducing our labour cost.

Making a wiring harness is expensive. Much of the assembly is done by people. Machines are very good at fitting tags and chopping wire to the right length. They are crap at assembling the harness into the right shape.

With CANbus much of the "wiring" is on printed circuit boards or in ribbon cables. These can be made by machines.

Final assembly of these PCBs and ribbon cables is also much cheaper as it reduces man hours considerably.

So, the benefit to you should be a cheaper product. However, I guess with BMW, they will just trouser any extra profit for themselves...

can i refer you back to post #9?

from what i've seen, the 1200 wiring looks much the same as an 1150, with little evidence of the pcbs & ribbon cables you mention.

 

[Yoda]

But I could still fix it with my swiss army knife, sitting on the roadside 100km outside Ouarzazate, couldn't I.....?

Switzerland isn't in the EEC and hence I feel it's unlikely that it will be compatible.

You'll need either a Belgian chip knife, or a Manchester screwdriver.

 

[TheWarlock]

R1150GS loom 3.125 kg
R1200 loom 2.450 kg

Well, I did say someone would be along.......

 

[Rob Farmer]

can i refer you back to post #9?

from what i've seen, the 1200 wiring looks much the same as an 1150, with little evidence of the pcbs & ribbon cables you mention.

There isn't. The only real Can-bus link on the 1200 is from the main processor to the Speedo/display unit everything else is just Input/outputs. Because the inputs are simply low voltage status inputs they have no need to carry any significent current which is why everything stops working at the slightest sign of any dirt or moisture - Should be Fine when everything is new and shiney but a pain in the arse a few years down the line when the connections and switch terminals start to corrode.

Ties you in nicely to the dealer network and theorecticaly allows for dumbing down of vehicle technicians because all they have to do is plug in a computer and it's diagnose the problem for them.