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I am communicating with a USB device (LED screen) serially, via ttyUSB0 (visible in /dev/ttyUSB0).

However, it will not power off on shutdown or on suspend. Only via the terminal command 'reboot' or if I close the software communicating with the device.

Does anyone know why? I've tried manipulating the settings in /sys/bus/usb/devices/usb1/power with little effect.

System: Debian 8 (Jessie)

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Do you mean that only the power/energy remains, or is the video signal also maintained?

If it's just about power, some USB ports, on some computer (like Lenovo), are set up to stay awake when the system shuts down / hibernate. It's called "Always On USB", and can be disabled from the BIOS

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  • Video signal is maintained too, i.e. it continues displaying the information before the suspend or shutdown. There are no options like that in the BIOS of this ITX board.
    – Cheetaiean
    Jul 21, 2021 at 18:28
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/bin/sleep 1 in a systemd/system-sleep shell script appeared to solve the issue - maybe the commmand makes the USB idle long enough for auto suspend to be activated.

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