CT-S280 adopts an USB-serial converter chip manufactured by FTDI.
The chip equips a virtual COM driver on the USB side only, so an instruction for CUPS is listed on below web site as an instruction of a virtual COM driver.

http://www.citizen-systems.co.jp/english/support/download/printer/driver/cups/source/vcom.en.html

You can download source files from below FTDI's web-site if you do not find files instructed on the above in Linux.

http://www.ftdichip.com/Drivers/VCP.htm

Virtual COM of printers except for CT-S280 is designed to be compatible with FIDI's chips. The instruction is applicable to virtual COM of other printers.
Note that each the operation of FIDI's chip and the virtual COM varies among different versions.

Our virtual COM is based on a specification of an old FTDI's chip. Some printers may recognize it as newer one.
Printers does not work properly (garbled characters) due to the recognition error.
To correct the error, change ID of USB described on the above site or run an additional batch file as below.

Apply the batch file "file ftdi_determine_type" in addition of "VID=0x2730,PID=0xfff" for CT-S280.
---------------------------------------------------------------------
The row described as "version = le16_to_cpu(udev-> …" is found in the first part.
Subsequently, add(not replace) the sentence "if( version == 0x002 ) version = 0x400;" just below the "if" sentence to make "bcdDevice” to be treated like 4.
---------------------------------------------------------------------
the changed setting may affect the operation in case that the same PC is connected with the device equipping a FTDI chip. The printer may print what appeared to be random garbage just after the connection even in the manner.