Disconnect and reconnect ttyUSB0 programmatically in Linux

Question

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.

Answer 1

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.