I need a usb to serial RS232 DB9 adapter to connect a printer. I bought an adapter with a very common-used Prolific PL2303XHD chip, but I have many many troubles with flowcontrol. I tried to switch to hardware than to software but this adapter always fails to manage flowcontrol and fills the printer's input buffer. I'm quite sure the problem is in this adapter because I also try with a pci serial board and with the same configuration the connection works stopping its flow while the printer are printing a long job. I tried to change the usb adapter, I bought another one, but inside I found the same chip and obviously it has the same problem. Do you have any experience with flowcontrol and usb-serial adapter? I can use both XON/XOFF or CTS/RTS flowcontrol.


  • When you use hardware flow control, are you using a connection/cable that supports the necessary 5 to 7 wires? – chux - Reinstate Monica Dec 26 '13 at 1:12
  • Yes, of course. Moreover I found a good chip: FTDI, it has a full XON/CTS support. – Tobia Dec 27 '13 at 10:57

For me the definitive answer is to use FTDI chip instead of Prolific.


I just replaced a FTDI with a PL2303 adapter because I was getting overrun error in Linux at 9600 and losing messages. The PL2303 has fixed the problem, no more overruns in DMESG.

  • 1
    How does your answer help OP please give more information – yass Apr 9 '17 at 14:10

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