CAN Bus, How our cars modules communicate
6/4/14, 07:13 PM
#21
A Man Just Needs Some....
6/4/14, 08:14 PM
#25
A Man Just Needs Some....
I just wanted a better explanation why everything has gone to CAN. What factors proved a need for it? Or was it just more unnecessary technology?
Honestly by this time I would probably prefer no answer at all.
6/5/14, 12:34 AM
#27
Mach 1 Member
Great read and breakdown of the can implementation.
I've been reading up on can as its huge for racing efforts to be able to tap into all the cars' built in sensors and calculations and bringing that into the telemetry picture to help drive competitive performance. There's a lot to learn from the outside looking in, however.
Also in VW/Audi land, apps like vag-com allow testing of those modules and changes with a interface that's almost friendly for end users (maybe not down to the sub-blue collar level alscobra trolls around in) but I hadn't seen a lot of equivalents on the ford side. I know there's some Chinese ebay kits out there and will be the first thing I try to see what I can learn and find.
I've been reading up on can as its huge for racing efforts to be able to tap into all the cars' built in sensors and calculations and bringing that into the telemetry picture to help drive competitive performance. There's a lot to learn from the outside looking in, however.
Also in VW/Audi land, apps like vag-com allow testing of those modules and changes with a interface that's almost friendly for end users (maybe not down to the sub-blue collar level alscobra trolls around in) but I hadn't seen a lot of equivalents on the ford side. I know there's some Chinese ebay kits out there and will be the first thing I try to see what I can learn and find.
6/5/14, 01:19 AM
#28
Bullitt Member
Wow this is waste of a read. Should have titled this one (look what I know).
Why do we need it? What are the advantages?
If you can tell me why we need to do it your way, maybe I might consider it. Unfortunately the answer usually is only the pursuit of technological advancements because it's not necessary. Lol
Why do we need it? What are the advantages?
If you can tell me why we need to do it your way, maybe I might consider it. Unfortunately the answer usually is only the pursuit of technological advancements because it's not necessary. Lol
I suppose you could use a simple handle to do the FLUSH; but, you're right, it wouldn’t be as cool!
I just use the lawn. Ha!
6/5/14, 08:38 AM
#29
A Man Just Needs Some....
Great read and breakdown of the can implementation. I've been reading up on can as its huge for racing efforts to be able to tap into all the cars' built in sensors and calculations and bringing that into the telemetry picture to help drive competitive performance. There's a lot to learn from the outside looking in, however. Also in VW/Audi land, apps like vag-com allow testing of those modules and changes with a interface that's almost friendly for end users (maybe not down to the sub-blue collar level alscobra trolls around in) but I hadn't seen a lot of equivalents on the ford side. I know there's some Chinese ebay kits out there and will be the first thing I try to see what I can learn and find.
6/5/14, 08:39 AM
#30
A Man Just Needs Some....
I think I can answer that. The engineers needed to come up with a CAN to handle the enormous amount of output created during a multi-module DUMP. The CANanalyser will display the programmed timing of the module FLUSH sequence which is how the PCM will know when to WIPE the BUFFER. You want to keep your BUFFER clean in case of a SHTF collision on the network. Otherwise you get 0x7B7 00 AA BB CC DD FF FF FA all over the place! I suppose you could use a simple handle to do the FLUSH; but, you're right, it wouldn’t be as cool! I just use the lawn. Ha!
6/5/14, 11:21 AM
#31
Legacy TMS Member
We already know that with current emmision controls, the PCM is needed to regulate and optimize the running of the engine.
Manufacturers also claim that there is less wiring, and that is the case. But it is also save money in the designing and manufacture.
For an instrument cluster, a supplier only needs to know what signals the cluster will receive, and are supposed to design and make the cluster for Ford based on these signals without worrying about how the signal needs to be generated.
I found this article that I found helpful:
Manufacturers also claim that there is less wiring, and that is the case. But it is also save money in the designing and manufacture.
For an instrument cluster, a supplier only needs to know what signals the cluster will receive, and are supposed to design and make the cluster for Ford based on these signals without worrying about how the signal needs to be generated.
I found this article that I found helpful:
Most carmakers buy the instrument clusters fully assembled from a supplier, who designs them to the carmaker's specifications. This makes the job of designing the instrument panel a lot easier, both for the carmaker and the supplier.
It is easier for the carmaker to tell the supplier how each gauge will be driven. Instead of having to tell the supplier that a particular wire will provide the speed signal, and it will be a varying voltage between 0 and 5 V, and 1.1 V corresponds to 30 mph, the carmaker can just provide a list of the packets of data. Then, it is the carmaker's responsibility to make sure that the correct data is output onto the communications bus.
It is easier for the supplier to design the instrument panel because he doesn't need to know any details of how the speed signal is generated, or where it's coming from. Instead, the instrument panel simply monitors the communications bus and updates the gauges when it receives new data.
These types of communications standards make it very uncomplicated for carmakers to outsource the design and manufacture of components: The carmaker doesn't have to worry about the details of how each gauge or light is driven, and the supplier who makes the instrument panel doesn't have to worry about where the signals are coming from.
It is easier for the carmaker to tell the supplier how each gauge will be driven. Instead of having to tell the supplier that a particular wire will provide the speed signal, and it will be a varying voltage between 0 and 5 V, and 1.1 V corresponds to 30 mph, the carmaker can just provide a list of the packets of data. Then, it is the carmaker's responsibility to make sure that the correct data is output onto the communications bus.
It is easier for the supplier to design the instrument panel because he doesn't need to know any details of how the speed signal is generated, or where it's coming from. Instead, the instrument panel simply monitors the communications bus and updates the gauges when it receives new data.
These types of communications standards make it very uncomplicated for carmakers to outsource the design and manufacture of components: The carmaker doesn't have to worry about the details of how each gauge or light is driven, and the supplier who makes the instrument panel doesn't have to worry about where the signals are coming from.
6/5/14, 11:50 AM
#32
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Wow this is waste of a read. Should have titled this one (look what I know). So to most people here, none of this informations matters. Now my ash tray and glove box can talk to my doors and transmission. One big communicating family under one roof. To a few that are trying to put factory accessories in their car from newer models, it matters a little I guess. But I have questions for all the engineers that obviously like to share knowledge. We all now know what CAN is from you guys now.
Why do we need it?
What are the advantages?
This is why I ask. They don't save on wiring. If anything it only complicated a very simple system or function. Now a switch or motor will not work because a module won't communicate. The systems are still 12V so what's wrong with switches and relays? They are reliable and proven. I don't design communication systems but my background is repairing them after you guys call them great. Diagnostics, reliability, and repairs, are something that is not a concern when you're in a cubicle. I deal with engineers every day. If you can tell me why we need to do it your way, maybe I might consider it. Unfortunately the answer usually is only the pursuit of technological advancements because it's not necessary. Engineers just need job justification and manufacturers like to say they have the latest technology even though they don't need it. It's high dollar bragging rights that cost us more in the long run. Thanks a lot guys. Lol
Why do we need it?
What are the advantages?
This is why I ask. They don't save on wiring. If anything it only complicated a very simple system or function. Now a switch or motor will not work because a module won't communicate. The systems are still 12V so what's wrong with switches and relays? They are reliable and proven. I don't design communication systems but my background is repairing them after you guys call them great. Diagnostics, reliability, and repairs, are something that is not a concern when you're in a cubicle. I deal with engineers every day. If you can tell me why we need to do it your way, maybe I might consider it. Unfortunately the answer usually is only the pursuit of technological advancements because it's not necessary. Engineers just need job justification and manufacturers like to say they have the latest technology even though they don't need it. It's high dollar bragging rights that cost us more in the long run. Thanks a lot guys. Lol
Steering Angele
Yaw Rate
Lateral Acceleration
Longitudinal Acceleration
Pressure Sensor
Vacuum Sensor
Engine Torque
Engine Speed
Wheel Speed Sensors
Park Brake apply status
Throttle Position
Brake pedal position
Clutch position
..... and so on
A lot of other modules also use the same information. So if you were to use relays and run separate wires to ESP module, ECM, BCM, PTM etc you would have a ridiculous web of wires running all over the car.
Instead, the ESP module reads in the Wheel Speed Sensors (hardwired), does filtering, processing, compensation and monitoring on them, and broadcasts the wheel speed to every other module that needs it on the CAN bus. 4 wires instead of 40. Same goes for quite a few other signals. And CAN bus has a well defined protocol so there is no voltage level/A2D conversion, or scaling issues to worry about.
Also now OEs are moving to Flexray because CAN isn't fast enough. As El Coyote said, the sheer volume of information transmitted is astronimical, and with semi-autonomous and fully autonomous features which we're working on now the volume needs and data transfer speed needs are higher and higher.
Is this sort of what you were looking for?
Last edited by 5.M0NSTER; 6/5/14 at 11:51 AM.
6/5/14, 03:27 PM
#33
A Man Just Needs Some....
I think the answer is simple. Look at the Electronic Stability Control system for example. It needs the following information: Steering Angele Yaw Rate Lateral Acceleration Longitudinal Acceleration Pressure Sensor Vacuum Sensor Engine Torque Engine Speed Wheel Speed Sensors Park Brake apply status Throttle Position Brake pedal position Clutch position ..... and so on A lot of other modules also use the same information. So if you were to use relays and run separate wires to ESP module, ECM, BCM, PTM etc you would have a ridiculous web of wires running all over the car. Instead, the ESP module reads in the Wheel Speed Sensors (hardwired), does filtering, processing, compensation and monitoring on them, and broadcasts the wheel speed to every other module that needs it on the CAN bus. 4 wires instead of 40. Same goes for quite a few other signals. And CAN bus has a well defined protocol so there is no voltage level/A2D conversion, or scaling issues to worry about. Also now OEs are moving to Flexray because CAN isn't fast enough. As El Coyote said, the sheer volume of information transmitted is astronimical, and with semi-autonomous and fully autonomous features which we're working on now the volume needs and data transfer speed needs are higher and higher. Is this sort of what you were looking for?
6/5/14, 03:36 PM
#34
A Man Just Needs Some....
We already know that with current emmision controls, the PCM is needed to regulate and optimize the running of the engine. Manufacturers also claim that there is less wiring, and that is the case. But it is also save money in the designing and manufacture. For an instrument cluster, a supplier only needs to know what signals the cluster will receive, and are supposed to design and make the cluster for Ford based on these signals without worrying about how the signal needs to be generated. I found this article that I found helpful:
Nobody cares about cluster or any other parts manufacturers. If they want the contract, they will build to work with whatever system the car uses. It's just technology for tech sakes. That's all it is. It's here now so were stuck with it till the next evolution but we definitely didn't need it for anything.
6/5/14, 05:27 PM
#35
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It's the better one so far. It's a whole lot of data transferred and collected. But how much of this data is needed? Other than maybe a near crash adjustment for the stability system, what use does it have? The dampers on your mustang don't adjust on their own. Brake pressure doesn't adjust much unless there is a traction loss. My point is it is unnecessary data and unnecessary technology. Stand alone systems would work much better and require less effort. Lighting, comfort, and entertainment have nothing to do with engine and emission controls. They don't need to communicate with the ECM at all. It's putting space shuttle technology in a red wagon. The mustang is still a pretty primitive vehicle as well as many of today's vehicles. In a tech and engineering world, it's cool and innovative. But real world usefulness it's overkill and just a waste. For the choice few people that will actually utilize this data, it might be a good thing. Like I said, engineers need job stability too and if they are not innovating, they don't keep their jobs. Leaving well enough alone is a good idea sometimes too though.
Think about autonomous braking alone. You have to have a radar/camera unit detecting objects and measuring the distance. Then it calculates a deceleration target/distance. The ECU has to communicate with the Camera/Radar sensors. Then the ECU has to send a brake request to the Brake ECU. The brake ECU must monitor wheel speeds, yaw, pressures, deceleration, it must communicate with the power train to ask for a engine tq reduction, apply the brake lights, notify all other systems that emergency braking is in progress, so cruise control knows to disengage and so on and so forth.
I work on some projects were in addition to the standard ABS, Traction Control and Stability control functions we offer over 35 value-added functions. This trend is also on the rise. And autonomous driving is coming. This makes the data demand and processing demand sky high. It's literally aircraft system like redundancy, and each ECU has to have 2 or 4 cores, memory protection, data integrity and fail-operational capability.
The nice thing about CAN is that ALL the information is on it, and everyone is networked together. Each module can just pick and chose what info it needs to do it's thing. In the last 5-7 years there has also also been a separation of different can busses. One project I work on has 3. One for driver info (and the many touch screens and wifi/4g controllers and infotainment on it, one for power train and drive train, the electric motors and batter, and one for chassis).
It's only gonna get worse. Enjoy your Mustang while it's still simple.
Last edited by 5.M0NSTER; 6/5/14 at 05:48 PM.
6/5/14, 06:48 PM
#36
A Man Just Needs Some....
Hey Als, I think you make some good points. It used to be more stand alone, but another trend in the auto industry today is centralizing, or combining more features into one ECU. Otherwise you'd have over 100 controllers all networked to one another in some way. Now there are ~35 or so. Now the trend is to combine as much as possible. For example the brake system ECU also performs electrical park brake duties, driveline protection, traction control, hill start assist, vehicle hold, full speed range cruise control, parental controls, autonomous emergency braking, trailer sway control, hill descent control, hydraulic boost force compensation, and about 25 other functions. To do this all, and do it safely when sub systems fail a tremendous amount of information is needed. Pus there are systems backing up other systems, so there is a need for redundancy of data availability. Think about autonomous braking alone. You have to have a radar/camera unit detecting objects and measuring the distance. Then it calculates a deceleration target/distance. The ECU has to communicate with the Camera/Radar sensors. Then the ECU has to send a brake request to the Brake ECU. The brake ECU must monitor wheel speeds, yaw, pressures, deceleration, it must communicate with the power train to ask for a engine tq reduction, apply the brake lights, notify all other systems that emergency braking is in progress, so cruise control knows to disengage and so on and so forth. I work on some projects were in addition to the standard ABS, Traction Control and Stability control functions we offer over 35 value-added functions. This trend is also on the rise. And autonomous driving is coming. This makes the data demand and processing demand sky high. It's literally aircraft system like redundancy, and each ECU has to have 2 or 4 cores, memory protection, data integrity and fail-operational capability. The nice thing about CAN is that ALL the information is on it, and everyone is networked together. Each module can just pick and chose what info it needs to do it's thing. In the last 5-7 years there has also also been a separation of different can busses. One project I work on has 3. One for driver info (and the many touch screens and wifi/4g controllers and infotainment on it, one for power train and drive train, the electric motors and batter, and one for chassis). It's only gonna get worse. Enjoy your Mustang while it's still simple.
And I'm glad to hear from someone actually working on these systems. I know you need job security and this looks a lot like an approval pitch to management. Lol.
But would you admit that it really is just unnecessary on a vehicle that will never see any of these options? Maybe it's just a good proving ground for the future but it causes a lot of hard parts to be completely obsolete if a car is wrecked and will kill a lot of aftermarkets also. Just doesn't seem like good business.
6/5/14, 06:53 PM
#37
Shelby GT500 Member
Geez I'm not asking you for sex. I doubt if you're my type of guy anyways. Get over yourself.
I just wanted a better explanation why everything has gone to CAN. What factors proved a need for it? Or was it just more unnecessary technology?
Honestly by this time I would probably prefer no answer at all.
I just wanted a better explanation why everything has gone to CAN. What factors proved a need for it? Or was it just more unnecessary technology?
Honestly by this time I would probably prefer no answer at all.
6/5/14, 09:04 PM
#39
Shelby GT500 Member
Sorry, I'm not skinny nor am I into any type of guys or guys at all. But...
I like big butts and I can not lie
You other brothers can't deny
That when a girl walks in with an itty bitty waist
And a round thing in your face
I get sprung!!
I like big butts and I can not lie
You other brothers can't deny
That when a girl walks in with an itty bitty waist
And a round thing in your face
I get sprung!!
6/5/14, 09:44 PM
#40
A Man Just Needs Some....
I am quite the booty aficionado myself.
Mostly girl booties.
