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Trying to solve this problem (ttyUSB0 that works properly than stop working after about 1hr)I'm thinking on if disconnecting and reconnecting the usb device could be a good fix.

So, it is possibile to cut down power to the USB device and repower it programmatically (bash)? 

# lsusb -t                                        
1-1:1.0: No such file or directory                                              
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=musb-hdrc/1p, 480M             
    |__ Port 1: Dev 2, If 0, Class=vend., Driver=, 12M                          
    |__ Port 1: Dev 2, If 1, Class=vend., Driver=cp210x, 12M

On am335x, kernel 3.2.0, ubuntu core armhf.

[    1.784332] usb 1-1: cp210x converter now attached to ttyUSB0

At the moment I need a complete power cycle to have ttyUSB0 back.

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JosephITA
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    If you find the solution to your own question, you should post an answer. You can even accept your own answer if noone offers a better one. – OJFord Aug 04 '14 at 10:49

2 Answers2

16

This is the solution:

  • Find the identity of your usb device.

    # tree /sys/bus/usb/drivers/cp210x/
/sys/bus/usb/drivers/cp210x/
|-- 1-1:1.1 -> ../../../../devices/platform/omap/musb-ti81xx/musb-hdrc.1/usb1/1-1/1-1:1.1
|-- bind
|-- module -> ../../../../module/cp210x
|-- remove_id
|-- uevent
 -- unbind

So 1-1:1.1 is the identifier of my ttyUSB0(it can be discovered also via dmesg).

  • Then, disconnect the device (as root):

    # echo -n "1-1:1.1" > /sys/bus/usb/drivers/cp210x/unbind

  • reconnect it

    # echo -n "1-1:1.1" > /sys/bus/usb/drivers/cp210x/bind

At this point I had the same device but with a different name, it was now ttyUSB1 instead of ttyUSB0. - To avoid this I added a new rule in /etc/udev/rules.d/ by creating a new file named 99-usb-serial.rules with this line:

SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea70", ATTRS{serial}=="002DCFAF", SYMLINK+="sameName", MODE:="0666"

where idVendor, idProduct and serial must be the values of your device. This rule will create a new device called sameName linked to the ttyUSB* device normally generated from the OS.

Robert Harvey
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    to get identifier of my device from dmesg i use this: `dmesg | grep ': pl2303 converter detected' |sed -e '$!d'| awk '{ print $2}'|sed 's/.$//'` – snex Sep 29 '17 at 09:57
  • but this doesn't, power off the usb serial device? how to power off the usb serial – 3bu1 Jul 13 '18 at 10:20
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As @Robert Harvey Said,

You first need to find our driver that will help you 'unplug and plug' the usb. Type: ls /sys/bus/usb/drivers which should print something like this: btusb ftdi_sio hub usb usbfs usbhid usbserial_generic uvcvideo. These, are all the drivers for each usb device. Now, lets say mine is ftdi_sio, which is a device i use to program my arduino (atmega328p chip). I am not sure how Your/other usb devices name themselves there. Like, i dont know which of these is my mouse. Now, you can see the driver's commands using: ls /sys/bus/usb/drivers/ftdi_sio/, which will print something like: 1-4:1.0 bind module uevent unbind, Where 1-4:1.0 is the device's characteristic code, and the bind and unbind command, which are the 'plug' and 'unplug' command respectively.

Now, if i want to unplug programatically the ftdi usb port, i will type: echo -n "1-4:1.0" > /sys/bus/usb/drivers/ftdi_sio/unbind and, to plug it again: echo -n "1-4:1.0" > /sys/bus/usb/drivers/ftdi_sio/bind

Now, we can combine all the commands together, with a ';':

echo -n "1-4:1.0" > /sys/bus/usb/drivers/ftdi_sio/unbind ; echo -n "1-4:1.0" > /sys/bus/usb/drivers/ftdi_sio/bind

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