request info on OBD II / CAN - Tilted Forum Project Discussion Community

Silvy · 11-24-2006, 01:19 PM

I'm trying to get to grips with collecting vehicle performance data.

The company I work for has performed analysis on such data in the past and is looking for the way to collect that data (vehicle speed, fuel consumption and such).

I've read up on the (E)OBD (I/II) standards. I've looked at some OBD-II scantools. We've worked with a CAN converter before...
Some questions remain however:

- What is the relationship (technology-wise) between OBD-II and CAN?
(I gather from tha intarweb that OBD-II is a request-answer protocol whereas the CAN bus can have broadcasting elements in addition to a question-answer system). Is the CAN bus just a main databus in the car, on which the (required) OBD-II plug is just a filter?
Or are they two separate ways of sending data through the vehicle?

- Is there a CAN-standard similar to OBD-II for which vehicle data is transferred? Is there a standard CAN-plug definition?

- Can you give me some pointers/opinions on hardware solutions for accessing basic vehicle metrics like vehicle speed, fuel consumption (such as provided by OBD-II).

The idea behind this is creating a manufacturer-independent on-board recording unit for basic vehicle data. OBD-II appears to be most commonly available, but from experience we know that the CAN bus on recent vehicle models contains a lot of interesting messages. So while OBD appears sufficient for now, if a CAN solution is feasible then it might be more interesting.

As I said, we've worked on the data before, and we've developed on-board hardware/software before. We've just never used that hardware to collect that data.

Right now I'm looking at some bluetooth OBD-II connectors that hopefully we'll be able to connect to and read with our current hardware (which is BT enabled).

lt1s10 · 11-25-2006, 05:42 PM

I don't know if a can solution would be something feasible right now. I only have some experience with Ford, BMW, Mercedes/Chrysler, and VW implementations. Because they all have implemented it in different ways using different software and hardware I don't think there is an easy way to interpret the data independent of the manufacturer yet.

What I see and think from working with the manufacturer scan tools and software is that the CAN bus is similar to one of the middle layers of the OSI (network layer or transport layer maybe) the upper layers (application layer) where the specifics lie are still very manufacturer dependant.

You may look into how Vetronix is capturing crash-data from cars. They do have a tool/software that will retrieve basic data at the time of the crash from supported manufacturers vehicles. I think the common factor here is that their SRS control modules probably share similar implementations between the manufacturers and vehicle models.

Another implementation you may look into is the X-431 scan tool from Launch. It's has wireless capture/logging abilities (may be bluetooth) and also supports CAN bus. They don't support all the manufacturers, data, or vehicles but so far it has the widest coverage of the generic scan tools I've been able to try and use. Other tools I've used are various Genisys tools, the Snap-On Modis, Inova, and the Matco scan tools (I believe these are rebadged Genisys tools). If you can get your hands on the manufacturer's tools then you may be able to figure out how they work. BMW and Ford are software based and run on laptops. As well as Vag-Com for the VW/Audi etc. cars.

Deltona Couple · 11-28-2006, 11:24 AM

CAN or "Candi" as is the common term is a completely different type of communication between different modules in a vehicle. CAN stands for "controller Area Network" It is the way which modules having the CAN wiring are able to communicate high speed information. It is totally different than the OBDII Which is STILL in use, and in most cases, works side-by-side with CAN. However the CAN network and OBDII network are on different communication wires, and are NOT interactive. The details would get too lengthy to try and describe here, so if you were a little more specific in what you need to know I would be glad to try and help.

11-24-2006, 01:19 PM	#1 (permalink)
Silvy paranoid Location: The Netherlands	request info on OBD II / CAN I'm trying to get to grips with collecting vehicle performance data. The company I work for has performed analysis on such data in the past and is looking for the way to collect that data (vehicle speed, fuel consumption and such). I've read up on the (E)OBD (I/II) standards. I've looked at some OBD-II scantools. We've worked with a CAN converter before... Some questions remain however: - What is the relationship (technology-wise) between OBD-II and CAN? (I gather from tha intarweb that OBD-II is a request-answer protocol whereas the CAN bus can have broadcasting elements in addition to a question-answer system). Is the CAN bus just a main databus in the car, on which the (required) OBD-II plug is just a filter? Or are they two separate ways of sending data through the vehicle? - Is there a CAN-standard similar to OBD-II for which vehicle data is transferred? Is there a standard CAN-plug definition? - Can you give me some pointers/opinions on hardware solutions for accessing basic vehicle metrics like vehicle speed, fuel consumption (such as provided by OBD-II). The idea behind this is creating a manufacturer-independent on-board recording unit for basic vehicle data. OBD-II appears to be most commonly available, but from experience we know that the CAN bus on recent vehicle models contains a lot of interesting messages. So while OBD appears sufficient for now, if a CAN solution is feasible then it might be more interesting. As I said, we've worked on the data before, and we've developed on-board hardware/software before. We've just never used that hardware to collect that data. Right now I'm looking at some bluetooth OBD-II connectors that hopefully we'll be able to connect to and read with our current hardware (which is BT enabled). __________________ "Do not kill. Do not rape. Do not steal. These are principles which every man of every faith can embrace. " - Murphy MacManus (Boondock Saints)

11-28-2006, 11:24 AM	#3 (permalink)
Deltona Couple Addict Location: Spring, Texas	CAN or "Candi" as is the common term is a completely different type of communication between different modules in a vehicle. CAN stands for "controller Area Network" It is the way which modules having the CAN wiring are able to communicate high speed information. It is totally different than the OBDII Which is STILL in use, and in most cases, works side-by-side with CAN. However the CAN network and OBDII network are on different communication wires, and are NOT interactive. The details would get too lengthy to try and describe here, so if you were a little more specific in what you need to know I would be glad to try and help. __________________ "It is not that I have failed, but that I have found 10,000 ways that it DOESN'T work!" --Thomas Edison

11-25-2006, 05:42 PM	#2 (permalink)
lt1s10 Crazy	I don't know if a can solution would be something feasible right now. I only have some experience with Ford, BMW, Mercedes/Chrysler, and VW implementations. Because they all have implemented it in different ways using different software and hardware I don't think there is an easy way to interpret the data independent of the manufacturer yet. What I see and think from working with the manufacturer scan tools and software is that the CAN bus is similar to one of the middle layers of the OSI (network layer or transport layer maybe) the upper layers (application layer) where the specifics lie are still very manufacturer dependant. You may look into how Vetronix is capturing crash-data from cars. They do have a tool/software that will retrieve basic data at the time of the crash from supported manufacturers vehicles. I think the common factor here is that their SRS control modules probably share similar implementations between the manufacturers and vehicle models. Another implementation you may look into is the X-431 scan tool from Launch. It's has wireless capture/logging abilities (may be bluetooth) and also supports CAN bus. They don't support all the manufacturers, data, or vehicles but so far it has the widest coverage of the generic scan tools I've been able to try and use. Other tools I've used are various Genisys tools, the Snap-On Modis, Inova, and the Matco scan tools (I believe these are rebadged Genisys tools). If you can get your hands on the manufacturer's tools then you may be able to figure out how they work. BMW and Ford are software based and run on laptops. As well as Vag-Com for the VW/Audi etc. cars.