Canbus wiring - Ducati Supersport 939 Forum
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post #1 of 28 (permalink) Old 11-10-2019, 10:21 AM Thread Starter
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Canbus wiring

I'm investigating adding the IMU to the SS harness. Blackbox etc will be changed too.

My question is whether or not adding wires onto the canbus Hi and Low wire which runs throughout all the electronic equipment, will it have an influence based on resistance and volt drops. If soldered then the volt drop will increase and maybe make some functions fail. I don't know, I'm hoping the knowledgable guys can provide some advice how I can integrate the IMU wires..
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post #2 of 28 (permalink) Old 11-10-2019, 01:54 PM
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So I'm not getting a clear picture of what you are trying to do in my head... However it sounds like you are modifying the existing harness to add components from another Ducati. I say if you match how the other harness is designed it should be fine.

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post #3 of 28 (permalink) Old 11-10-2019, 03:14 PM Thread Starter
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I think the penny has dropped.
The voltage is merely a carrier for the data packets. Voltage drop shouldn't impact it. The canbus is the network cable carrying lots of bytes of info. I'm a bit old and slow but I figured it out in the end.
Onward and upward!!!

Last edited by amoslws; 11-10-2019 at 03:42 PM.
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post #4 of 28 (permalink) Old 11-11-2019, 01:25 AM
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I'm not so sure. by adding wires + component will definitely change the values and therefor would be read differently unless it is within the programmed variables. I spent a lot of time talking to people who knew a lot about the Cam Bus on various Ducati. and always the news wasn't good if changes were made. A common problem in the past was the loom heating up from not being insulated enough and that would cause false readings. My understanding is that you would have to know the whole protocols and cause and effects and have the ability to reprogram the ECU / Black box and I just don't know how you would get that info. An example being if understand it right The rear tail light and the Fan motor (as well as other things )share the same message route to the computer. if the bulb goes on the tail light, the values are predictable and a warning light is triggered (Lamp out) but if the engine temp rises it sets off the Fan regardless of the tail light being out. I know we all know this but if the fan motor has stopped working (The protocol would put it into limp mode all based on the values returned to the Black box) My point is if you change the value you wont know till you turn your indicator on and it throws your bike into limp mode. The spent Months trying to find the Fault and cause of !!!!! in my Loom and gave up (and that was with confirming the values of all components being correct.
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post #5 of 28 (permalink) Old 11-11-2019, 02:29 AM Thread Starter
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Quote:
Originally Posted by Rhino View Post
I'm not so sure. by adding wires + component will definitely change the values and therefor would be read differently unless it is within the programmed variables. I spent a lot of time talking to people who knew a lot about the Cam Bus on various Ducati. and always the news wasn't good if changes were made. A common problem in the past was the loom heating up from not being insulated enough and that would cause false readings. My understanding is that you would have to know the whole protocols and cause and effects and have the ability to reprogram the ECU / Black box and I just don't know how you would get that info. An example being if understand it right The rear tail light and the Fan motor (as well as other things )share the same message route to the computer. if the bulb goes on the tail light, the values are predictable and a warning light is triggered (Lamp out) but if the engine temp rises it sets off the Fan regardless of the tail light being out. I know we all know this but if the fan motor has stopped working (The protocol would put it into limp mode all based on the values returned to the Black box) My point is if you change the value you wont know till you turn your indicator on and it throws your bike into limp mode. The spent Months trying to find the Fault and cause of !!!!! in my Loom and gave up (and that was with confirming the values of all components being correct.
Thanks for the warning... or scaremongering
Each sensor is allocated data codes, for example 02XX could be the tail light faulty and 0X20 could be headlight faulty. I don't know what all the codes are but I'm guessing they are the same as the error codes found using the obd reader. When operational the eproms are passing on the relevant codes for input and reaction.
Those numerous operational codes are transferred to each of the eproms on the canbus network and each eprom is programmed to give their output. Like the fuel injection for traction control, the dash eprom pings a light and the main ecu cuts the fuel, the Blackbox registers it and sends the code to each of the eproms and then they each react.
I intend going the full hog and change all the eproms so that each can work seamlessly. Namely, abs, dashboard, Blackbox, ecu, and IMU.
I have decided not to solder the IMU wires in incase there's an issue.
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Last edited by amoslws; 11-11-2019 at 02:33 AM.
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post #6 of 28 (permalink) Old 11-11-2019, 04:06 AM
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Iím not sure I get what your wanting to do and why. What is the end game ? Iím sure you know but Iíve read through and Iím missing something.
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post #7 of 28 (permalink) Old 11-11-2019, 04:08 AM Thread Starter
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I found this on Google and it is this that worries me.

"The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines"

I suspect these wires are 18awg since they are not current carriers. Can lines are milli amp carriers.

It could be fruitful if some of the electrical / electronic fundies could join in. Unless we don't have any members with that background of course.
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post #8 of 28 (permalink) Old 11-11-2019, 06:09 AM
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The CAN bus is a twisted pair with a termination resistance of 100Ω. I'm unsure where you get the idea that a soldered joint will drop volts as it will have less resistance than practically any other kind of joint and therefore have a minimum voltage drop and with the tiny currents involved probably next to none.
Quite a lot of good info here : https://www.csselectronics.com/scree...us/language/en
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post #9 of 28 (permalink) Old 11-11-2019, 06:35 AM Thread Starter
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Quote:
Originally Posted by Derek View Post
The CAN bus is a twisted pair with a termination resistance of 100Ω. I'm unsure where you get the idea that a soldered joint will drop volts as it will have less resistance than practically any other kind of joint and therefore have a minimum voltage drop and with the tiny currents involved probably next to none.
Quite a lot of good info here : https://www.csselectronics.com/scree...us/language/en
Twisted pair for cancelling the variance in electrical noise.
Intuitive video you posted. Cheers.
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post #10 of 28 (permalink) Old 11-11-2019, 09:12 AM Thread Starter
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@Derek
I see you've had online conversations in the MS forums regarding the canbus decoding. I have zero programming knowledge, well I did some at university over 25 yrs ago but it was not my thing, per say.
Do you know of any friendly solutions for reading, decoding and developing. Just wondering if you'd dabbled in it.
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