The solution to the problem that occurs when running handsfree_hw

Problem Description

Error with timeout when running roslaunch handsfree_hw handsfree_hw.launch.

Open the terminal and enter the command to see if there is a handsfree usb device
```
lsusb
```
Open the terminal and enter the command to see if there is a /dev/HFRobot device
```
ls /dev/HFRobot
```

Check if there are handsfree usb devices and /dev/HFRobot device

If there is neither handsfree usb device nor /dev/HFRobot device , it may be the following problems
- The robot is not powered on
- The USB serial cable is not plugged in properly or is not plugged in correctly
- The master control has a hardware failure or the connection inside the robot is loose
If there is a handsfree usb device but no /dev/HFRobot device character, it may be the following problems
- When configuring the development environment, there is no set usb rule, resulting in the USB device not being mapped to /dev/HFRobot, please refer to Configuring ROS and HandsFree Development Environment, reset the usb rules.
If /dev/HFRobot deviceis found, it may be the following problems
- The handsfree_hw driver is run repeatedly, or the driver that was run last time did not exit normally, resulting in the USB serial port device still being occupied by the previous program. Restarting the computer can solve the problem. Solution: Please use "ctrl+c" instead of "crtl+z" to exit the handsfree_hw program every time.
- The robot firmware program version and the host computer driver version do not match.