How to enable USB-Serial Port adapter (RS-232) in Ubuntu Linux

Though some might argue that Serial port are things in the past, it is still the most popular port for those who are into electronic DIY. Building electronic device with serial port interface is cheaper than buiding one that uses USB. That is the reason why people still sell USB-Serial adapter to those electronic DIY enthusiast.

Here’s how to enable USB-Serial port adapter in Ubuntu Linux (with credit to Freeman from RepRap forum)


Linux DIY USB Serial Port Adaptor

First plug in the USB-Serial Port adaptor to one of your USB port. Wait for a couple of second, then run “dmesg”. You should see these message at the end of dmesg output.


usb 1-1: new full speed USB device using uhci_and address 2
usb 1-1: configuration #1 chosen from 1 choice

After that, unplug the device and type “lsusb”. You will see a list of output similar to this.

Bus 003 Device 001: ID 0000:0000
Bus 002 Device 007: ID 03f0:4f11 Hewlett-Packard
Bus 002 Device 006: ID 05e3:1205 Genesys Logic, Inc. Afilias Optical Mouse H3003
Bus 002 Device 004: ID 15d9:0a33

Plug in the USB-Serial Port converter back, and run “lsusb” again, and you shall see an additional line, like this.


Bus 003 Device 001: ID 0000:0000
Bus 002 Device 007: ID 03f0:4f11 Hewlett-Packard
Bus 001 Device 002: ID 4348:5523 --- --- --- (notice the additional line!)
Bus 002 Device 006: ID 05e3:1205 Genesys Logic, Inc. Afilias Optical Mouse H3003
Bus 002 Device 004: ID 15d9:0a33

Now we know the vendor id and the product id of the USB-Serial Port converter, this will enable us to load the linux kernel module “usbserial” to activate the device, like this :


sudo modprobe usbserial vendor=0x4348 product=0x5523

Run “dmesg” again and you shall see lines similar like this :

usbserial_generic 1-1:1.0: generic converter detected
usb 1-1: generic converter now attached to ttyUSB0
usbcore: registered new interface driver usbserial_generic

As you can see, the new serial port device is mapped to /dev/ttyUSB0. You can instruct Ubuntu to load this module automatically by include the line : “usbserial vendor=0x4348 product=0x5523″ inside “/etc/modules” file.

Bonus: What application benefits from usb-serial port adaptor?
For starters, there are modems which uses RS-232 serial port. Some home-made devices includes Infrared remote control which uses LIRC which also depends on the serial port.

I use the adaptor to hook up my morse keyer in order to send morse code through the internet using Xchat CWIRC plugin. The site has an excellent circuit diagram to build such interface.

You can see my home-made morse code oscillator here : My Homemade Morse Code Practice Oscillator

Where can I get USB to Serial port converter?
You can get it from your local computer stores or order it online !

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