Canbus description help

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windmill john
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Canbus description help

Postby windmill john » Sat Jun 23, 2018 5:07 pm

Okay, don’t get too technical!
I get the reduce wiring, I get it’s about signals to and fro.

Okay, I know my way round a carb and normal wiring.... sort of!

My Luddite view is, if canbus gets old, nightmare.

Can someone calm my fevered brow.

Is there a Fisher Price, dorling kindersley guide to canbus?

If I bought a newish canbus bike and I generally rely on me to work on them, how much grief am I in!

I’d like to think if I had a buggered heated grip, I could tap into the wiring etc, fit a relay and fit some aftermarket grips. Is this out of the question with canbus.

I need an overview, but not a high brow overview, my brain would explode.

Cheers

John
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!

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Galactic Greyhound
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Re: Canbus description help

Postby Galactic Greyhound » Sat Jun 23, 2018 6:04 pm

John,

You are familiar with computers - think of CanBus as a programmable logic box with lots of input and output ports.

All the 'Inputs' such as Horn button, Starter Button, Headlight switch, Heated grips switch etc are connected to the Input Ports.

All the 'Outputs' such as the Horn, Starter Relay, Headlight, Heated grips etc are connected to the Output ports.

There are NO direct physical connections between the Input ports and the Output ports.
The connection is made by the software logic programming e.g.

HORN PROGRAMMING:

1. IF the Horn button Input port is operated (short circuit across Port) THEN send +12v to the Horn Ouput port (Horn sounds).

2. IF the current in the Horn Output port exceeds 7 Amps then shut down Horn Output port.
(There are NO fuses with CanBus, the software determines if unsafe current is flowing and cuts the power to the Ouput circuit. Power will be restored when the current flowing in the Output circuit does not exceed the programmed value).


If a logic Input/Output circuit fails e.g. Horn, you can physically wire an aftermarket Horn button, Horn and Horn relay (if desired) via an Ignition switched +12v supply and in-line fuse to bypass the CanBus Horn circuit.
Ced.

R1100RT 1996.
Sent by Boson Quantum Transmission from the Starship 'Galahad'.
http://www.researchgate.net/publication ... ing_bosons" - It works!

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Re: Canbus description help

Postby Mjolinor » Sat Jun 23, 2018 6:37 pm

As far as testing it goes it is very easy to just make sure that both wires go where they should. It is a two wire system with "differential signals" << Google that if you want to know why or I will explain if you want.

The thing that often gives problems is that a can bus should be terminated at each end with a 120 ohm resistor (Usually internal to the end device). This is one of the first things to check. If someone has added to the can then it may or may not have the termination inside, if it has and you put it in the middle of the can wiring it can give problems, if it hasn't and you put it at the end of the can then that too can give problems. If you measure the resistance between the two can wires then it should be 60 ohms ( 2 X 120 ohms in parallel). If you see 120 then you have a broken wire somewhere, if you see infinite resistance then you have two broken wires, one either way on the bus. Anything other than that needs more investigation.

The starting point for checking is always the OBD socket itself, that will have both can wires on it so buzz from there to everywhere it should go if your resistance between the two is not 60. Check for shorts to ground or 12 volt.

It is simple and easy but be careful because there may be more than one can bus depending perhaps on signal priorities. An injection signal for example will be a lot higher priority than a horn with ABS being somewhere in between those two. It is not hard to work out the priorities but more often now the low priority stuff is done with LIN rather than CAN as it is a one wire protocol so cheaper.

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windmill john
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Re: Canbus description help

Postby windmill john » Sat Jun 23, 2018 8:20 pm

Thanks chaps.

Ced, I got your input/output description.
Mjolinor, I think I need to reread yours. I appreciate your help. I’m one of those guys who finds some circuitry a little confusing, when return feeds for example go through a Miriad of devices and therefore cause some confusion when troubleshooting. Although saying that, I am offay with circuit testing on a bike, not at the electronic level.

What is the affect of corrosion on can bus wiring? I imagine higher resistances cause different affects than on ‘normal’ circuits.
What is the canbus equivalent of a multi meter? Or is there different diagnosis equipment to each make?

Thanks

John
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!

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Re: Canbus description help

Postby Mjolinor » Sat Jun 23, 2018 8:35 pm

The bus does not go "through" it really is just two wires that each device connects to.

The terminations are only on the end devices. The designer of the vehicle knows which devices those are and fits the correct resistance only in those devices.

In terms of understanding the way they are wired just imagine a battery with two wires 5 yards long and you have a series of bulbs with short wires. Where ever you connect the bulb wires between the two battery wires it will light up, as many as you want. CAN is the same, any devices you want connected across the two CAN wires.

As far as the communication goes you should start by thinking that there is one master device and it can request a connection to any of the slave devices on the CAN.

The actual CAN spec allows for multi master but generally in practise on a vehicle there is mostly just one master. The multi-master gets complex in terms of collisions and re transmissions but I think you should just know that it is possible, you are unlikely to ever be troubled by multi-master problems.

Broken wires are the most common problem by a long way, followed by a short to ground or between the two CAN wires. A transmitter fault that does not totally destroy the comms is very rare but also fairly easy to trace as you disconnect each item from the bus it will suddenly spring back to life when you disconnect the faulty device. Often if one of the CAN devices has failed there will be a fault stored in the ECU pointing to a can bus error from a particular device.

It is worth reading the wikipedia page: https://en.wikipedia.org/wiki/CAN_bus

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windmill john
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Re: Canbus description help

Postby windmill john » Sat Jun 23, 2018 8:54 pm

Thanks Mjolinor, a bit clearer now :smile:

Looking at the last bit, I guess that is what the GS911 is for, just read about it, didn’t know about it.

I bought a basic OBD-11 for my car which helped tremendously when a coil pack packed up. A £50 item saved me taking the car in.

John
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!

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DEEP DIVER
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Re: Canbus description help

Postby DEEP DIVER » Sat Jun 23, 2018 9:06 pm

Thanks chaps.


What is the affect of corrosion on can bus wiring? I imagine higher resistances cause different affects than on ‘normal’ circuits.

Thanks

John
Hi John, I can tell you if you get any corrosion it can cause loads of issues. We had a forklift a few years back with corrosion inside the fuse block and it sent the canbus loopy!
Another fault on the same type of truck was the truck computer which controls everything made it engage fwd and rev at the same time.
Give me good old wiring any day.
I tried to be normal once, worst two minutes of my life.
Blue belt in Serious tea drinking.

Barry the old goat!!!!
1985 R80ST being rebuilt #-o
1985 R80RT Touring dream :smile:
2 Harley sportsters being rebuilt #-o
And a VW trike so I don't fall off :shock:

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windmill john
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Re: Canbus description help

Postby windmill john » Sat Jun 23, 2018 9:24 pm

Lord knows what will happen when I stop using acetylene lighting for my headlight! :wink:

I just need to be dragged kicking and screaming into the 21st century.

Know my way around points, grey mist descends on latest electrickery
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!

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DEEP DIVER
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Re: Canbus description help

Postby DEEP DIVER » Sat Jun 23, 2018 9:42 pm

Lord knows what will happen when I stop using acetylene lighting for my headlight! :wink:

I just need to be dragged kicking and screaming into the 21st century.

Know my way around points, grey mist descends on latest electrickery
Headlights are a easy fix. Firebugs.
And that electrickery stuff you can get online in a paper bag. #-o

You should think about a hot bulb engine, works great.
I tried to be normal once, worst two minutes of my life.
Blue belt in Serious tea drinking.

Barry the old goat!!!!
1985 R80ST being rebuilt #-o
1985 R80RT Touring dream :smile:
2 Harley sportsters being rebuilt #-o
And a VW trike so I don't fall off :shock:

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raesewell
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Re: Canbus description help

Postby raesewell » Sun Jun 24, 2018 5:17 pm

Think of CanBus as an electronic fuse, if there is a problem with a circuit CanBus shuts it down until the problem is fixed.
That's the simplest way to explain it.

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Galactic Greyhound
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Re: Canbus description help

Postby Galactic Greyhound » Sun Jun 24, 2018 5:55 pm

..……...
You should think about a hot bulb engine, works great.

...and I thought it worked off the headlamp..... :sad:

https://en.wikipedia.org/wiki/Hot-bulb_engine
Ced.

R1100RT 1996.
Sent by Boson Quantum Transmission from the Starship 'Galahad'.
http://www.researchgate.net/publication ... ing_bosons" - It works!

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windmill john
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Re: Canbus description help

Postby windmill john » Sun Jun 24, 2018 6:24 pm

Not changing the subject, but the bike I was looking at was sold to a friend of the owner...

It was the the twin 650GS, hence the canbus question.

I did look at the earlier 650, but am very surprised how low it is!! 30 inch seat height with the normal seat, 1 inch off the ground with the lower seat :roll:

Schorsch is 34 inches, I am surprised at a traillie being four inches lower!!!!
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!


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