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As previously mention in this article, I had been happily using a serial console cable on my Macs (here after known as an SCC) (mine is an Aten UC-232A) without incident, until I upgraded my Mac Book Air to Lion.  Then it all broke again.

Here’s what I had to do to fix it…

First, I had to download the new 1.4.0 driver from here.  But that is only the start of it.  You need to follow the instructions contained in the Zip file and once the driver is installed, boot the Mac.

Next you need to edit the Plist file to reflect your actual hardware.  It is owned by root so you will need to sudo to be able to edit it. You need to plug your SCC and use System Profiler to get it’s Product ID and Vendor ID.  Remember these are in Hex, but when you edit the Info.plist the entries are in Decimal.  I found it easier to create a whole new <dict> entry rather than trashing the original installed by the driver.

Mine looks like this in System Profiler

Product ID: 0x2008
Vendor ID: 0x0557  (ATEN International Co. Ltd.)
Version: 3.00
Speed: Up to 12 Mb/sec
Manufacturer: Prolific Technology Inc.
Location ID: 0x04100000 / 4
Current Available (mA): 500
Current Required (mA): 100

So…

sudo vi /System/Library/Extensions/ProlificUsbSerial.kext/Contents/Info.plist

I added the following section after the original <key>067B_2303</key> Section

<key>0557_2008</key>
<dict>
   <key>CFBundleIdentifier</key>
   <string>com.prolific.driver.PL2303</string>
   <key>IOClass</key>
   <string>com_prolific_driver_PL2303</string>
   <key>IOProviderClass</key>
   <string>IOUSBInterface</string>
   <key>bConfigurationValue</key>
   <integer>1</integer>
   <key>bInterfaceNumber</key>
   <integer>0</integer>
   <key>idProduct</key>
   <integer>8200</integer>
   <key>idVendor</key>
   <integer>1367</integer>
</dict>

Once this is complete and saved you need to unplug the the SCC (very important) and load the edited kext file.

sudo kextload /System/Library/Extensions/ProlificUsbSerial.kext

Plug the SCC back in and do an ls on /dev and you should see your SCC in there now.  Mine looks like this…

crw-rw-rw-  1 root    wheel      18,   6  9 Feb 13:42 tty.usbserial

So if all has gone well you can now connect to your serial device again. For me that is any number of Cisco Routers or switches and the command is…

screen /dev/tty.usbserial 9600

Have Fun!