We are using Cables Unlimited USB-2925 USB-to-Dual-DB9 serial cables, which use the Moschip MCS7720 controller. We have downloaded the newest driver from http://www.moschip.com/mcs7720.php, but that driver was last updated in 2005. It does not seem to be working with Macs running OS X 10.6 Snow Leopard.

We have sent emails to the support addresses for both Cables Unlimited and Moschip. Cables Unlimited says they are checking with Moschip. No responses from Moschip yet.

Does anyone know of any updates for this driver, or are there any ways to get the driver to work with Snow Leopard?


Update: When MosChip updated their website (and, shortly thereafter, their management), they bounced driver downloads to ASIX Electronics Corp.. The latest(?) available version is v1.0.0.8, dated 08 March 2007, which is the same version as that listed in @pridkett's comment, below, but not the same date (his link says 22 Jan 2010). It's described as being for "10.4 - 10.2", x86 and PowerPC, but who knows...

Here are drivers for other OSes, and drivers for other MosChip / Axis / MCS77xx and MCS78xx chips.

(Thanks to @pridkett for pointing out that the original links had disappeared from MosChip).


There is a solution to force this exact cable to work with Snow Leopard while waiting for Moschip to update their drivers.

Be very careful while you are making this change. You will need to execute these commands as the root user.

  1. Install the latest driver from Moschip and reboot.

  2. Locate the file /System/Library/Extensions/MCS7720Driver.kext/Contents/Info.plist

  3. Open the file and locate the line that reads <integer>30496</integer>

  4. Change the number from 30496 to 30485. Save the file.

  5. Execute the command "touch /System/Library/Extensions".

  6. Wait a few minutes and plug in your USB cable. You should see a screen pop up that alerts you that two new network interfaces have become available. You'll note that they're named /dev/tty.USB-Serial0.0 and /dev/tty.USB-Serial1.1.

  7. You're good to go. If the software is ever updated by Moschip, it will likely overwrite this change.


Unfortunately, I don't have a suggestion for drivers for the controller you're currently using. I've always found the Keyspan High Speed USB Serial Adapter (USA-19HS) to be an excellent product for my USB-to-Serial needs and it is well supported under Mac OS X (including Snow Leopard, although I haven't tested this yet).


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