How to change SocketCan bitrate at runtime?

[mauriciocirelli]

Dear,

I would like to implement an auto-baud feature in my application. The idea is to probe the bus for incoming messages until we find the right bitrate from a list.

Is it possible to do that using socketcan interface? If so, how could I do that? Do I have to create new bus instances everytime I change the bitrate or can I reuse the same instance?

Thank you!

[felixdivo]

This is how you set the bitrate: https://python-can.readthedocs.io/en/stable/interfaces/socketcan.html#real-device. I don't think that can be done with syscalls when that interface has already been created but I didn't look at the socketcan specification.

[mauriciocirelli]

I see. I was hoping for a Python API. I think I will have to run this shell command from my Python app. Thank you. Em qui, 18 de abr de 2019 18:27, Felix Divo <notifications@github.com> escreveu:

…

This is how you set the bitrate: https://python-can.readthedocs.io/en/stable/interfaces/socketcan.html#real-device. I don't think that can be done with syscalls when that interface has already been created but I didn't look at the socketcan specification. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#549 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAIVLG33TDKZOG6MCMYZWSLPRDRSVANCNFSM4HFLERWA> .

[hardbyte]

Maybe we could make an abstract driver interface and implement socketcan calls as a Python api.

[mauriciocirelli]

It seems that it is possible using ioctls:

https://stackoverflow.com/questions/45967947/setting-socketcan-bitrate-programmatically

The source code for libsocketcan is here:
https://github.com/lalten/libsocketcan/blob/gh-pages/src/libsocketcan.c

There is a can_set_bitrate function that use system calls to setup the netlink.

[felixdivo]

I would like to implement an auto-baud feature in my application

You could also implement this in the library

[iurly]

Hi @mauriciocirelli,

I'm also interested in such a feature, did you manage to get around this issue?
So far I've been calling sudo ip link (which would be the equivalent of what libsocketcan does) using subprocess.call() , but that raises a few issues with sudo being required and configured.
I assume the same would apply to the equivalent syscalls made from within the python application (whether from pure-Python or a C extension).
Did anyone get around this somehow?
Thanks!

[mauriciocirelli]

Hi, I am doing the same... The difference is that I do not need (nor have) sudo as I am working on a embedded system. But it would be great to have such feature in the API. Mauricio Cirelli www.futuragames.com.br Em dom, 13 de out de 2019 às 10:22, iurly <notifications@github.com> escreveu:

…

Hi @mauriciocirelli <https://github.com/mauriciocirelli>, I'm also interested in such a feature, did you manage to get around this issue? So far I've been calling sudo ip link (which would be the equivalent of what libsocketcan does) using subprocess.call() , but that raises a few issues with sudo being required and configured. I assume the same would apply to the equivalent syscalls made from within the python application (whether from pure-Python or a C extension). Did anyone get around this somehow? Thanks! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#549?email_source=notifications&email_token=AAIVLGYY5W5MHTJUP6RTV6LQOMOLBA5CNFSM4HFLERWKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEBCWFSI#issuecomment-541418185>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAIVLGYULWA2MXECGQXTYC3QOMOLBANCNFSM4HFLERWA> .

[cperkulator]

Maybe we could make an abstract driver interface and implement socketcan calls as a Python api.

So would a PR be welcomed to do something like:

def change_baudrate(self, baudrate):
    raise NotImplementedError()

in the BusABC.

Also when it relates to changing the baudrate on socketcan, it looks like there are a couple options:

• libsocketcan
• pysocketcan
• netlink sockets directly

Does anyone have any experiences with these? Or is there a suggestion for a place to start with switching baudrate on socketcan?