Reseting USB from script

[Aivaras]

Hello, 
I was wondering if there is a command that would allow me to reset USB port? 
I am using LM5 Lite and I'm using USB for rs232 communication, but the problem I have is it sometimes hangs and does not send nor receive any commands and the only way I can make it come back alive is rebooting LM, so maybe only rebooting USB port would be a possibility?

[admin]

Check system log in system config. Most likely your USB device reconnected and changed the port name from /dev/ttyUSB0 to /dev/ttyUSB1.
You can use this function to find the port name. It will return nil if no port is found.

Code:

function findport()
  local path = '/sys/bus/usb-serial/devices'
  local ports = io.ls(path) or {}

  if type(ports) == 'table' and #ports > 0 then
    return '/dev/' .. ports[ 1 ]
  end
end

You should check for read errors to detect USB disconnect:

Code:

res, err = port:read(...)
if err == 'read error' then
  -- USB disconnected
end

[Aivaras]

Check system log in system config. Most likely your USB device reconnected and changed the port name from /dev/ttyUSB0 to /dev/ttyUSB1.
You can use this function to find the port name. It will return nil if no port is found.

Code:

function findport()
  local path = '/sys/bus/usb-serial/devices'
  local ports = io.ls(path) or {}

  if type(ports) == 'table' and #ports > 0 then
    return '/dev/' .. ports[ 1 ]
  end
end

You should check for read errors to detect USB disconnect:

Code:

res, err = port:read(...)
if err == 'read error' then
  -- USB disconnected
end

Hello admin,

Unfortunately the problem is still here.

USB does not change the port name. err displays: timeout

system log puts out:

Apr 24 13:57:01 LogicMachine kern.err kernel: [14656.417881] pl2303 1-1:1.0: pl2303_vendor_write - failed to write [0000]: -110
Apr 24 13:57:01 LogicMachine kern.err kernel: [14656.297931] pl2303 ttyUSB0: pl2303_get_line_request - failed: -110
Apr 24 13:57:01 LogicMachine kern.err kernel: [14656.177891] pl2303 ttyUSB0: pl2303_set_control_lines - failed: -110
Apr 24 13:57:01 LogicMachine kern.err kernel: [14656.057986] pl2303 1-1:1.0: pl2303_vendor_write - failed to write [0000]: -110
Apr 24 13:57:01 LogicMachine kern.err kernel: [14655.937909] pl2303 ttyUSB0: pl2303_set_line_request - failed: -110
Apr 24 13:57:01 LogicMachine kern.err kernel: [14655.818029] pl2303 ttyUSB0: pl2303_get_line_request - failed: -110
Apr 24 13:57:00 LogicMachine kern.err kernel: [14655.697920] pl2303 1-1:1.0: pl2303_vendor_write - failed to write [0009]: -110
Apr 24 13:57:00 LogicMachine kern.err kernel: [14655.578120] pl2303 1-1:1.0: pl2303_vendor_write - failed to write [0008]: -110
Apr 24 13:57:00 LogicMachine kern.err kernel: [14655.457913] pl2303 ttyUSB0: error sending break = -110


Any solutions? Or maybe I can restart USB port?

[admin]

Try a different USB adapter. PL2303 is not very stable from my experience. Use CP2102 or genuine FTDI chips.

[Aivaras]

Try a different USB adapter. PL2303 is not very stable from my experience. Use CP2102 or genuine FTDI chips.

Hello admin,

I have replaced USB adapter with genuine FTDI chip (FT232RL). The problem is still here. Any other ideas?

[admin]

Are you using an extension cable? Most likely there's a noise source nearby that's causing USB interference.