CODEWITHSUNDEEP
pythonlinuxusb
Eric Hewett
Eric Hewett

Reputation: 557

How do identify a USB modem /dev on LINUX with Python

If I have a USB modem that I am accessing using Python pyserial module, it requires the device to be identified '/dev/ttyACM0 for example. If the modem is attached to a USB hub it no longer appears in /dev/tty...

How do identify it programmatically from my Python code so regardless of whether it has been changed or not, or the machine rebooted I can locate the modem?

Note: I can always see the device using lsusb, but if it is attached to a USB hub it does not appear as /dev/tty... device

Upvotes: 2

Views: 4902

Answers (2)

tuomur
tuomur

Reputation: 7098

Instead of doing some voodoo in Python, try writing a udev rule which gives your device a much more useful name like /dev/my-serial-thingy. Using that from Python is way easier.

Upvotes: 1

Aaron Digulla
Aaron Digulla

Reputation: 328754

This sounds like a bug in the linux kernel. If you can, try a more recent version.

If that fails, check the last few lines of the output of dmesg or in the file /var/log/messages (the latter depends on your distribution; if that file doesn't exist or doesn't contain what you're looking for, then check the other files in /var/log; sorting by time with ls -rt helps).

After identifying the device, you might see a pattern.

Another approach is the major and minor number. If you run ls -l /dev, you'll see output like this:

crw--w----   1 root tty         4,   0 2011-12-19 09:15 tty0

The c means "character device" and the 4, 0 means it's the console device unit 0.

The 4 is the major number which identifies the type of device. See /proc/devices for a list of major numbers and the respective device drivers.

If you plug in the model directly, note the major number. After plugging it into a hub, try to find devices with the same number.

Upvotes: 1

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