USB to RS232 driver PL2303 doesn't work on Mac OS X 10.6.8


I wonder if anyone could help me out here.

I’ve followed instructions at… to install the PL2303 driver, version 1.5 on my macbook pro running os x 10.6.8. After restarting my mac, I checked my system profiler and found the device is still not being recognised. Please see the screenshot. !](](

I then tried to remove it by running:
sudo rm -rf /System/Library/Extensions/ProlificUsbSerial.kext
and reinstall it a few times didn’t help either.

Also I followed tips from this web page:…, didn’t work for me either.

I’m really stuck now, don’t know if this usb to rs232 convertor is going to work on my mac at all? Thanks for any suggestions.

Hi Binjie,

Thank you for contacting us about your USB to Serial adapter. I’m sorry you are having troubles with it.

The adapter and driver should work without any problems with OS X 10.6.8.

We have a tool that can gather the appropriate system information to help troubleshoot this.

Could you install the driver (…), plug in the USB to Serial adapter, then follow the instructions for Mac at:
It’s at

Also, if you haven’t already, could you try plugging it directly into each USB port on your Mac, just to make sure a USB port issue isn’t the problem?


Plugable Support

Hi David

Thank you for your reply. I’ve given up on that USB-serial convertor, changed to a FTDI USB serial convertor and seems ok. At least it’s showing up in the system profiler correctly.
But when I tried to screen the usb port it doesn’t give me anything back at all, just a blank screen. See the command below:
screen /dev/cu.usbserial-00001004 115200
Any ideas?

Many thanks.

Hi Binjie,

I can’t say about the FTDI device, but if I plug two Plugable USB to Serial adapters connected by a null modem cable into my Mac mini, open two terminals, and issue screen /dev/cu.usbserial 115200 in one terminal, and screen /dev/cu.usbserialx (x=the number assigned to the second adapter) 115200 in the other, I can pass data back and forth between the two. I’m running OS 10.8.4, but I don’t think that should make a difference.

If you cd to the /dev directory and do an ls, do you see the /dev/cu.usbserial device, or any cu.usbserialx devices? You should also see a tty device.

Actually, the /dev/cu.usbserialx command should give you a blank screen. What you type there will go out the port to whatever is attached to it. And whatever comes in through that port should be displayed.