Raw data from can bus

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nothin
Posts: 5
Joined: Sat Feb 25, 2017 7:42 pm

Raw data from can bus

Post by nothin »

Hello

I've been trying to get raw data from the can bus to the serial output, using datalogger as an example. However, datalogger seems to have a filter so it only sends out the pids that was requested. I would like to have either the entire can bus frame or something divided in ID and data, for processing on a computer.

Does anybody have a sketch with only this output or could point me in the direction, it would be nice.

For clarification, I am not interested in freematics data. All I want to, is read what is continously written on the can bus line by the car.

Regards
protomor
Posts: 99
Joined: Wed Oct 14, 2015 9:17 am

Re: Raw data from can bus

Post by protomor »

The OBD2 port is an interface to the CAN BUS system. It is not direct access to it. The port will only answer to commands. Each PID you poll responds within a certain time frame. So you could theoretically throw the whole PID book at the port. But each request will take time to respond. I'd imagine a full round would take at minimum a few seconds.

Short answer: No. Inherently what you want is not possible through the OBD2 port.
nothin
Posts: 5
Joined: Sat Feb 25, 2017 7:42 pm

Re: Raw data from can bus

Post by nothin »

Thank you for your reply.

What goes trough the obd port is manufacturer dependent. I know for a fact that some cars, uses a double can bus system, where the obd will be connected to one can bus system and will request from the other can bus system. As you described. Other cars, on the other hand, only has one can bus, which is directly wired to the odb port.

I tried hooking up the port to an oscilloscope which showed constant data transfer when nothing was connected. This is the data that I want to read.

But if I were to go through all the enabled pids of a car, would I then get all the information that the car offers or are there parts of the car that does not respond to a pid request?
protomor
Posts: 99
Joined: Wed Oct 14, 2015 9:17 am

Re: Raw data from can bus

Post by protomor »

The OBD2 port ONLY responds to certain things. Manufacturers purposefully block things from fully being read through the port. So you cannot read everything from that port. What you want to do is what car manufacturers specifically try not to let you do.
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