High Speed USB UART  Board  Question & Answer


 Persistent names for usb-serial devices


Q: Is there a way in Linux to fix the /dev/ttyUSBx assignment for a specific FT232 ? When I have more than one plugged into a system, the /dev/ttyUSBx assignments get shuffled and this breaks scripts that I have written.

 Fix ttyUSB0 to ttyCOM1

 1. Every USB device has a Vendor ID and a Product ID as seen for instance in lsusb output:


2. find serial number for each USB serial Port

udevadm info -a -n /dev/ttyUSB0 | grep '{serial}' | head -n1


3. find other USB device information use 

udevadm info --name=/dev/ttyUSB0 --attribute-walk


4. make udev rules

inside the /etc/udev/rules.d  make file  99-usb-serial.rules

SUBSYSTEM=="tty",ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A504W0XN", SYMLINK+="ttyCOM1"
SUBSYSTEM=="tty",ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A504W0XQ", SYMLINK+="ttyCOM2"
SUBSYSTEM=="tty",ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A504W0XO", SYMLINK+="ttyCOM3"
SUBSYSTEM=="tty",ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A504W0XP", SYMLINK+="ttyCOM4"


5 .reboot  &  check system

use command    ls /dev     you will see ttyCOMx  & ttyUSBx


6. use command   ls -l /dev/ttyCOM1   check



*** 4x USB UART/8x USB UART application

Setting Serial Console Server with ser2net


1. search USB port in your system

dmesg | grep tty  


2.install ser2net  software 


sudo apt-get install ser2net -y


3. Configuration

sudo nano /etc/ser2net.conf


make ser2net.conf to telnet from other Pi or PC


BANNER:banner:\r\nser2net port \p device \d [\s] (Debian GNU/Linux)\r\n\r\n

2000:telnet:600:/dev/ttyCOM1:9600 8DATABITS NONE 1STOPBIT banner
2001:telnet:600:/dev/ttyCOM2:9600 8DATABITS NONE 1STOPBIT banner
3000:telnet:600:/dev/ttyCOM3:9600 8DATABITS NONE 1STOPBIT banner
3001:telnet:600:/dev/ttyCOM4:9600 8DATABITS NONE 1STOPBIT banner


4 from another Pi use telnet to the serial port

install telnet     use command  sudo apt-get install telent


Host Name

telnet ?
usage: telnet [-l user] [-a] host-name [port]


telnet pi4-4p.local  3000





    udev.sh        - collect 4 USB serial number and save file for udev rules

    udev8.sh     - collect 8 USB serial number and save file for udev rules 

   p4-send-order.py    -  send 4 port in order to make sure ttyUSB0, ttyUSB1...ttyUSB3

   p4-u8-send-order.py  -  send 8 port in order to make sure ttyUSB0,ttyUSB1....ttyUSB7



    Green LED ON in order TXD,TXD2,TXD3,TXD4  to make sure ttyUSB0,ttyUSB1..ttyUSB3 in correct order.



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