Serial ADTPro communication

Subjects covered in this post:
Mac OS X serial drivers
Serial cables
I don’t know about you but I was raised to make use of what you had, and if you had fun along the way then you’d learned something.  I certainly did, with this blog post spelling out where I had troubles establishing a working serial connection between any of my laptops and the Apple Super Serial Card.  I could have spent money on the suggested cables and adaptors or even splurged on an Uthernet II

This post may be a tedious read and is intended more for documentation should someone have connectivity issues like I did that are not addressed in the excellent ADTPro website. I referred to this website countless times and if you’re going down the same path you will too.

Serial communication on Mac OS X 10.11 El Capitan, where to begin.  I had two USB to Serial adapters in the collection, a silver Dolphin Peripherals and a more solid-looking one with no label.  The Dolphin Peripherals seemed the better choice (wrong) as it had an LED indicator light and a model number.  My mac wouldn’t recognise the device as a serial port so I set about finding drivers.

Dolphin USB to Serial Adapter
Model No: XH6451
Chipset:  FT8U232AM

The fact that Mac OS X supports an extreme range of printers with over 168 pages of drivers drivers, it does not include built in support for once common chipsets as made by Prolific and FTDI.

Fun fact: Mac OS X lists my serial device as both, like “/dev/tty.usbserial-A700dYoR” and “/dev/cu.usbserial-A700dYoR.  Keith Kaisershot explains that “tty” == TeleTYpe and “cu” == “Calling Unit.  Martin Crockett further elaborates “tty is the traditional Unix name for serial ports as in to connect a serial terminal. cu is also a serial port but traditionally used to connect two systems together, a bit like ADTPro connections.”
I was able to find Mac drivers thanks to this Whirlpool Forum thread which support PowerPC-based Apple computers.  No worries I thought – after all one of the great advantages to having an Apple computer collection is being able to walk over to shelf and pick out the model I need, where I chose an iBook G4 running 10.5.5 and installed the drivers which worked as ADTPro would recognise it as TTY or CU serial port.

There is a glitch though – reboot the computer and the serial port is lost.  A technical note I found explains
2. The device cannot be accessed after the computer has

The background to this problem is that FTDIUSBSerialDriver has a dependency on  This is an Apple driver and it is not a Root driver.  This means
that at “root” (boot) time, the driver’s dependencies cannot be satisfied, and the driver does not participate in the extension loading process.

Apple’s position on this problem is as follows :-

“Apple will not (for the foreseeable future) be able to provide a root version of  It depends on other components that are not available at boot time.”

This presented a serious annoyance as ADTPro could crash (for me) if the disk transfer was interrupted on the Apple IIe which was happening randomly.  I would have to hard reboot the iBook and reinstall the driver every time.  This situation was almost enough for me to give up on the idea as it also meant I had to have another computer on my computer desk for at least as long as it took to image the educational software I had.   I decided to keep using the iBook and Dolphin serial adapter with the limitations for the time being.

Note: I even went as far as swapping my SSC for a spare which was an earlier revision.
Moving on to connecting the Apple Super Serial Card (SSC) to the USB Serial adapter.  The SSC uses a DB-25F (25-pin female) port and the USB serial adapter a DB-9M (9-pin male).  I went to storage tub which had a DB-9M to DB-9F cable in new condition and a DB25 to DB9 converter.  This was supposed to be the solution – all the plugs fitted and it wasn’t uncommon to use a solution like this with a modem as I had experienced all those years ago when dialup was a thing.

I had the cable, working serial port, and ADTPro server software ready.  Nothing I tried could get the ADTPro client software running on a real Apple IIe to talk to the Macbook.  I blamed the USB Serial adapter and grabbed a Dell Precision laptop with 32-bit Windows XP on it and a real COM port.  What a time suck.  Would you believe the laptop was running Windows XP Service Pack 2 and Java needs service pack 3?  Would you believe the Microsoft support page for downloading a network install .exe of SP3 redirects to a Windows 10 upgrade page?

Needless to say I persevered like I always do and found a slow mirror for XP SP3 and installed the latest version of Java for XP.  Updates completed I ran ADTpro, connected up the Apple II to the ‘real ‘ COM port expecting things to finally work.  They didn’t.  Same problem as before – no communication between the Apple IIe and computer.

I wrote to the Apple ][ Australia mailing list to basically debrief my frustration and see what trouble shooting options I had.

At this point I considered anyone who had ADTPro working a magician as I had tried everything I could, and decided to walk away from the project for a few days to regroup.  A new cable and adapter from the USA possibly offered a solution but the thought of buying another serial cable and the postage costs to Australia pointed me back to doing things the hard way and using what I had

I decided a new cable was needed and went to a local charity store where I found a  direct DB-25 to DB-9 cable.  Plugged it into the Dell Precision and ADT worked immediately.  The literal second I chose the Bootstrap option that text flew across my IIe screen!

Finally a working solution.  It was the cable the whole time, or more specifically an incompatible DB-25 ->DB-9 adapter.  Feeling energised I went back into a storage tub to just see what the other USB-Serial adapter was like.

Believe it or not, it was the very adapter ‘the interwebs’ suggest as the very best for Mac OS X compatibility – a Prolific 2303.  The first result in Google gave me appropriate drivers for 10.11 which worked, so armed with the right serial cable AND the best USB to Serial adapter I set to work making a spreadsheet to appropriately document the floppy disks and feeding them through my DuoDrive (cleaning the drive heads every so often of course!).

You’ve read this far to learn a genuine Prolific 2303 chipset-based adapter is failsafe thanks to current supported drivers and use only direct 25-pin to 9-pin cable to the Apple SSC.


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