Add support for ISO TP

[hardbyte]

Originally reported by: toonst (Bitbucket: toonst, GitHub: toonst)

---

Support for ISO TP is not yet built in SocketCAN by default, but there exists an implementation:
https://github.com/hartkopp/can-isotp

It would be great to be able to use this from python-can.

Since I really could use this functionality, I might take stab at implementing it. Could someone list the changes that are needed to make it work? I'm not familiar with the python-can code, so I don't know if this is feasible.

---

• Bitbucket: https://bitbucket.org/hardbyte/python-can/issue/45

[hardbyte]

Original comment by Brian Thorne (Bitbucket: hardbyte, GitHub: hardbyte):

---

This is very feasible. Every interface has been contributed by someone different.

Take a browse through the can/interfaces folder and at the BusABC in can/bus.py. Do you think you can write a concrete implementation that is compliant with the abstract base class?

[christiansandberg]

As I understand it ISO TP is a small protocol layer that abstracts away the limitations of regular CAN like the 8 byte limit. Other real protocols like UDS uses this. On one hand it could make sense to have this here since it is closer to the CAN layer and not an actual protocol. On the other hand it makes sense to keep python-can clean from everything but the lowest level.

[felixdivo]

On the other hand it makes sense to keep python-can clean from everything but the lowest level.

I agree with this and would recommend implementing that in a new repository if someone decides to do this. We can still link from one to the other and python-iso-tp can depend on python-can.

We could also consider making something existing compatible with python-can, like https://github.com/pylessard/python-can-isotp.

I would suppose we close this ancient issue after we decided on that.

[inorick]

python-can-isotp is only a wrapper around the Linux kernel‘s native ISO-TP implementation and not an implementation of the protocol itself. The only one in pure Python that I could find is part of pyvit and it only implements a subset. So I think unless there is another dedicated ISO-TP project, python-can would be a good place for a platform independent implementation of ISO-TP.

[felixdivo]

Okay, I'm fine with that as long as it resides in it's own package (like isotp), and not in can.*. Btw.: Pull Requests are always welcome. ;)

[felixdivo]

Also see socket.CAN_ISOTP.

[christiansandberg]

That would also just work for socketcan. I think we can close this issue since it is easy and cleaner to keep protocols in separate packages.

[felixdivo]

Well, as long as no one has the time to tackle this, I doesn't matter anyway.

[hardbyte]

This also lines up with what we did for the J1939 protocol which was to put it in an external library - https://github.com/milhead2/python-j1939

Agree we should link to these higher level libraries from our docs.

[polybassa]

Hi, I we created an ISOTPSoftSocket inside the Scapy project. This ISOTPSoftSocket can use any python-can interface object for the lower layer. Unfortunately, we didn't wrote the docs, yet. Usage examples can be found in the unit-test-file. Just search for ISOTPSoftSocket https://github.com/secdev/scapy/blob/26eac7e85fd89af2e71c85dcf7fea8416103fbe9/scapy/contrib/isotp.uts#L967.
Maybe this is useful for someone.

[syntroniks]

Some hardware interfaces have support for ISOTP.
The Neovi devices from ICS will both send and accept flow control frames. You can send >8 bytes and the interface/driver handle the rest. Receive calls return individual frames, however.

[christiansandberg]

@pylessard is implementing support for python-can in udsoncan now and I have implemented an asyncio ISO-TP library.

[pylessard]

Actually, the IsoTP layer is implemented in can-isotp module which I use in udsoncan. The IsoTP implementation is functional but not released yet.

[polybassa]

Well, the downside of the can-isotp implementation is the fact, that it runs only on linux and python3. If you have, for example a Vector interface or you are forced to use windows, you can not use Hartkopp's isotp kernel moduls.

[pylessard]

Sorry for the confusion. There is a python implementation, I just haven't updated the documentation yet, give me a week or 2. Vector on Windows works, I tested it with some hardware. I'll write an example on how to use it with Vector soon. In the mean time, you can have a look at the isotp.protocol module, you should find what you are looking for.

[polybassa]

Alright. Thanks for this information. I'm always interested in other approaches. I'll leave you one or two remarks.

[pylessard]

This is now fully supported by can isotp and can be used with python-can.