Reseting USB from script

[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