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CanBus ?


Janson

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Some one mentioned that¬† the T7 are wired via Canbus ,¬† in a tread abaut fitting usb socket . How can that be , i mean all those fuses does not comput with canbus ore are im out saling here ?¬†ūü§Ē

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Excelent question, I really don't think there is a can-bus system on the T7? I can't really find any mention of it in the service manual.

RTW Ténéré 700, UK to India & back on Honda CB500X

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Indeed . Lots of talk abaut CanBus on the forum . BUT ! CanBus systems do NOT need fuses as the computer will shut down faulty systems . Futher more  less cables are needed and this is the gain . Less weight ! 

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19 hours ago, Janson said:

Indeed . Lots of talk abaut CanBus on the forum . BUT ! CanBus systems do NOT need fuses as the computer will shut down faulty systems . Futher more  less cables are needed and this is the gain . Less weight ! 

Not necessarily. It depends on how the ECM is configured.

-audifan

 

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CAN bus doesn't mean solid state. If you run electrical switching via solid state circuits then you can use logic rather than fuses and relays. But if you walk out and look at your car you will find a fuse box or two with ease. And all vehicles currently use some for of CAN language. A CAN bus is nothing but a two wire computer network that "speaks" in a specific language. It is only there to transfer data which requires very little power. Sometimes that data asks a device to function, but that doesn't mean that circuit doesn't need to be protected by a fuse. It also doesn't mean you cant use power wires on the bike for other items. 

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For a CAN bus system to work you have to have a module at either end of the communications circuits. I can't see them putting a module in a power plug because there is no need for this when it can be done an easier way. A CAN bus consists of at least 2 controller modules and 2 circuits, a CAN Hi and a CAN Lo with a resistor joining the 2 circuits at each end which is usually incorporated in the modules. I can't see anything that looks like a CAN bus in the wiring diagrams. I can see a communication wire from the Engine Control Unit to the ABS Electronic Control Unit, but it is only a single wire so can't be a CAN bus. I'd say it's a serial data circuit that communicates at high speed between the Engine Control Unit  and the ABS, seeing as the front and rear wheel speed signal goes directly to the Engine Control Unit. This is a white and yellow wire.

Edited by Whitey66
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15 minutes ago, sbeck09 said:

CAN bus doesn't mean solid state. If you run electrical switching via solid state circuits then you can use logic rather than fuses and relays. But if you walk out and look at your car you will find a fuse box or two with ease. And all vehicles currently use some for of CAN language. A CAN bus is nothing but a two wire computer network that "speaks" in a specific language. It is only there to transfer data which requires very little power. Sometimes that data asks a device to function, but that doesn't mean that circuit doesn't need to be protected by a fuse. It also doesn't mean you cant use power wires on the bike for other items. 

The CAN bus circuit itself is protected by the terminating resistors at each end of the can bus. I've never seen a fuse on a CAN bus but would be happy to be proven wrong, there are fuses protecting the modules that contain the CAN bus, but not on the CAN bus circuits. You can't just tap into a CAN bus for power, it's for communication only.

Edited by Whitey66
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"CAN Bus" is a networking standard for microcontrollers - it's a way for the various controllers in a vehicle to send messages in the digital domain, rather then using analog signals such as PWM, resistance, varying voltages and so on. Other examples of networking standards are Ethernet and WiFi. ODB2 works on the Canbus standard, so any vehicle with OBD2 technically has a Canbus system.

 

There are three controllers that I count in the T7, that form three nodes in a Canbus network. The engine controller - 'ECU', the ABS controller and there is also a controller in the dash board display (which Yamaha refer to as the 'meter') These form three nodes in a Canbus network. OBD2 works using the Canbus standard - so if you connect a scan tool, you essentially have a fourth node in the network.

 

Canbus does not have a host or server node. Any connected controller can send a message and it can be read by any connected node. It's akin to sitting in a group and talking (which might seem like a foreign concept given current world conditions ūüôā ). One person speaks and everybody hears it. But what each person does with that information is up to them.

 

 

An example of Canbus in use on the T7 would be: (note i'm assuming most of this based on engineering intuition & experience. This level of detail is something manufacturers typically do not publish, certainly not in the service manual because it's somewhat irrelevant to vehicle repair.)

 

The ABS controller has a direct connection to the wheel speed sensors and continually reads the wheel speed. The Engine ecu and dash board meter do not have this connection. 

The ABS controller sends a Canbus 'message' with a reading of the speed. (the front wheel speed, usually)

The ECU reads that message and uses the speed data to calculate and record the odometer reading.

The meter controller also reads the message and uses it to display the speed to the rider.

 

The ECU sends a message containing the odometer reading, which the meter controller reads and displays.

 

The ECU can determine the engine speed. It then sends a Canbus message with the current engine speed:

THe ABS ecu ignores the message because it's not fundamental to the operation of anti-lock braking systems.

However the meter does read the message and displays the engine speed.

 

 

If you want to delve into the more nefarious side of things - Canbus does not have any security measures. Messages are often very short and in very basic formats using no encryption. This makes it susceptible to 'man in the middle' attacks. An example of such an attack would be a device that sits between the Canbus network and the meter controller. This device reads every incoming message. It passes through most all messages unmolested - but when it detects an odometer reading message, it alters the message before passing it on. That's how to 'roll back' the odometer on a modern vehicle ūüėČ

 

 

 

 

 

 

 

 

 

 

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16 minutes ago, Whitey66 said:

The CAN bus circuit itself is protected by the terminating resistors at each end of the can bus. I've never seen a fuse on a CAN bus but would be happy to be proven wrong, there are fuses protecting the modules that contain the CAN bus, but not on the CAN bus circuits. You can't just tap into a CAN bus for power, it's for communication only.

Correct, we agree. I should have been more clear. My point was that the bike having a CAN bus wouldn't stop you from tapping power like any other harness. You just have to make sure you arent using the CAN wires.

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I just had a better look at the wiring diagram on my PC instead of my phone, looks like there is a CAN bus joining the Engine Control Unit, the ABS and the instruments. The blue and black, and the blue and red wires are the comms. The speed signal goes into the Engine Control unit then communicated to the other modules from there.

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  • 2 weeks later...
On 5/29/2020 at 5:30 PM, sbeck09 said:

Correct, we agree. I should have been more clear. My point was that the bike having a CAN bus wouldn't stop you from tapping power like any other harness. You just have to make sure you arent using the CAN wires.

Yes, and another thing you have to be careful of is running other non genuine wiring next to the CAN bus wires that may interfere with the signal. The CAN bus wires are usually twisted together to reduce the chance of this happening and this is called a "twisted pair"¬†, and no, i'm not talking about King Jong-un and Donald Trump¬†ūüėĚ

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On 6/6/2020 at 4:14 PM, Whitey66 said:

Yes, and another thing you have to be careful of is running other non genuine wiring next to the CAN bus wires that may interfere with the signal. The CAN bus wires are usually twisted together to reduce the chance of this happening and this is called a "twisted pair"

I can  tell you from experience that the CAN wires are low frequency and not known to cause interference, but they are susceptible to it. Interference is typically an issue near ignition wires. Given that the coils are mounted on top of the engine, this can become an issue pretty easily with motorcycles due to limited space. The best way to protect signal wires from this is by using shielded wire. The outer layer is grounded with these. We do it all the time with cars/trucks. 

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