Please skip this part if your serial port is called /dev/ttyUSB0. Only proceed if this is not the case.

If you do not know what your serial device is called, you can do the following.

• Disconnect the serial device and run ls /dev/tty*. Did you notice something missing compared to the previous printout?
• Now connect the serial device, wait 5-10 seconds and run ls /dev/tty* again. Do you see a new device in the list?
• If you do not see a new serial device, the device may not be compatible with Linux. Run dmesg to see if it is detected. In my case it is detected, and is named ttyUSB0:

• To update the vmodem.sh script stored in /boot/vmodem/, do the following:
• Edit /boot/vmodem/vmodem.sh by running sudo nano /boot/vmodem/vmodem.sh
• Find the line serport=ttyUSB0 and update it to reflect the correct serial device. For example, if your USB device is called “ttyAMA0”, then type in serport=ttyAMA0.