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I have a RS232C/USB cable to connect an electronic device to my iMac Intel (MacOSX SnowLeo 10.6.3).

Is there a utility program that allows for sending ASCII characters on the USB port that the RS232C device will understand?

If possible, I'd rather avoid programming. I'd prefer an Automator script or a simple program with a GUI.


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Normally your cable should have a Prolific PL-2303 component to implement USB to serial port. Drivers can be downloaded here. Once installed you can use a terminal emulator to send characters to your device. You have these choices (untested for me as I don't have the hardware with me):

  • use ZTerm (It is very old and shareware)
  • use and see this article
  • use QuickTerm (might be the best solution, but again untested)
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I'm still waiting for my USB/RS cable (from HK). I'll give a try to QuickTerm as soon as I get it. Will let you know – Olivier May 24 '10 at 23:21

You will not interact with the USB device. The USB device should provide drivers that will create a virtual serial device in /dev/ when you plug in your device. Once the device is plugged in and the driver has created the virtual serial device, communication takes place over the callout device file /dev/ or the TTY device file /dev/xxx.tty (where xxx is particular to your driver). Communication might be as simple as catting a text file with stdout redirected to that path. Failing that, a serial-aware interface such as those mentioned by CharlesB might be necessary. If you are looking for a command line tool, try socat, which has flags to configure the baudrate, parity, and bitwidth of messages sent across a serial port.

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