SocketCAN problem

Support Cyphal & UAVCAN
1

Hello,

I am trying to use the Babel module with Ubuntu 20.04.4 LTS in a C++ program.

The module is connected through an USB interface, and via CAN bus to a µC that only sends heartbeat messages.
Using “uavcan_gui_tool” this heartbeat message is displayed and updated.

In my C++ program I am using the socketcan.h/cpp and libcanard libraries.
After launching

sudo slcand -o -s8 -t hw -S 3000000 -F /dev/serial/by-id/usb-Zubax_Robotics_Zubax_Babel_320042000757424E3430302000000000-if00

with the answer

[5] attached TTY /dev/serial/by-id/usb-Zubax_Robotics_Zubax_Babel_320042000757424E3430302000000000-if00 to netdevice slcan0

in the C++ program the socketcanInit (&ifCAN, “slcan0”) returns 0, the ioctl() with SIOCGIFFLAGS returns IFF_RUNNING, but the write() in socketcanTransmit() returns with errno==ENETDOWN…

Any hint?

Thanks!

2

I think you need to bring the iface up, like ip link slcan0 up. Here’s a script that is more convenient than running slcand manually:

Not directly related but new applications should be using OpenCyphal.

3

Thank you Pavel! I’ll try this tomorrow.

4

It works flawlessly (the exact command is

sudo ip link set up slcan0

).

Thanks again Pavel!