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Thread: My Computer Has No Parallel or Serial Ports

  1. #1
    Join Date
    Nov 2005

    My Computer Has No Parallel or Serial Ports

    [edited from a support email:]

    I just had a quick question about having DRT send out ttl signals.

    I've read the relevant documentation about how to specify the byte value/port location/time, but am having difficult figuring out the port location.

    I've read the extended documentation about how to find the address of the parallel and serial port in the hardware profile, but the thing is that my computer doesn't have a serial or parallel port, only USB ports.

    I have a USB to parallel adapter so I can interface with a Biopac machine, but I send out at ttl. I've looked for the hardware profile of the USB device in the manager, but can't figure out what the port value would be. One lead is in under Details --> Device Instance
    ID. It gives me the following string:


    Not sure if there's an address somewhere in there. So, I'm not sure if you have any suggestions on how to get a ttl signal when there are no parallel or serial ports, but I would greatly appreciate any ideas you have on the matter.

  2. #2
    Join Date
    Nov 2005
    If you've purchased a new computer in the past few years, there's a decent chance that the legacy ports (serial, parallel & joystick) have been replaced by USB ports.

    While the USB bus is a powerful way to send lots of data back and forth between a computer and multiple peripherals, it's not as hacker-friendly as the legacy ports were.

    At the time of this writing, DirectRT will only work with ports having a physical (and electrical) address inside the computer. So USB-Serial and USB-Parallel adapters are out.

    That being said, we're working on some modifications to make DirectRT work with emulated serial ports. But we're not ready to go public with the new code yet. Soon, though!

    However, companies such as www.jameco.com sell 'Parallel Interface Cards' which connect to your computer's internal expansion slots. Voila - a 'real' parallel port that DirectRT can talk with. Check out their part #171927 for reference.

    They also sell serial interface cards. #171362 looks promising.

    USB-parallel ports adapters will never work with DirectRT or MediaLab.

    They're useful if you need to bring an old printer back to life, but not for much else. Windows, unfortunately, restricts their functionality to driving printers only. It's not possible to toggle individual data pins back and forth like you can with a standard parallel port.

    MediaLab, however, can send and receive data through a generic USB-Serial interface. At $40 or so, these interfaces emulate a regular COM port and allow your new computer to communicate with legacy peripherals.

    If you dig a bit deeper in this hardware forum, you'll find a sample MediaLab script which works well with an emulated serial port.

    So the short answer is this: if you need serial capability, MediaLab will work with regular serial ports as well as USB emulated ones. DirectRT will work with regular serial ports, and *soon* will work with emulated ports.

    If you need a parallel port and your computer doesn't have one, consider switching machines or (if possible) buying a third-party parallel port card.

    By the way, these cards are great for general hacking. Because if you make a mistake and blow one up, you're out $40 - which is better than replacing an entire motherboard.

    If you get that far, let us know and we'll walk you through the process so your experiments will run properly.


  3. #3
    Join Date
    Sep 2006

    I wanted to share my successful experience in this regard. I wanted to run DirectRT on a MacBook Pro (Intel CPU-based Apple laptop, using Windows XP installed under BootCamp), and send TTL codes to my EEG system. Since the MBP (like all Apples) has no parallel port, this was a problem. The MBP does, however, have an ExpressCard34 port, which is on the PCI bus (i.e., the same bus you'd plug a parallel port card into on a desktop computer). On the web, I found an ExpressCard-to-parallel adapter. There are several out there; I ordered this one, based on the fact that they would ship to Canada and had a customer-friendly return policy if the card didn't work for my application.

    Installing the card was simple, just a matter of installing the driver off the included CD and then pluggin the card in. The trick to getting it working was finding out what its hardware address was. Unlike a built-in parallel port, this one does not show up in DirectRT's TTL I/Otest application. So, as described in DirectRT's documentation, I went to Control Panel -> System -> Hardware -> Device Manager -> Ports (COM & LPT) and selected the card. One of the tabs allows you to set the port as LPT1, 2, or 3, but this had no effect on its detectability by TTL I/Otest. But, under the Resources tab the hardware address(es) of the port are given in Hex format. Converting this to decimal using Window's calculator app (again, as described in the DirectRT manual), I got a port address and entered that manually in TTL I/O test. Then I tried sending a 10 msec TTL code to the EEG system, and by gar it worked! Entering the same port address into a DirectRT script also worked.

    I encountered two "gotchas" in getting this to work. The first was that at some point in my testing, the hardware address of the port actually changed. Still haven't figured out if this was after a reboot or unplugging then re-plugging the card (BTW, be sure to use "Safely uninstall hardware" tool in the Taskbar to turn the card off before popping it out), but suddenly I was not getting codes, until I went back to the Hardware Profiler and found that the address had changed (actually, first I bugged Blair and then I figured this out ). The second 'gotcha' was that in TTL I/Otest, at the offset of every code I send, my EEG system registers a '255' code. This does not occur when I send codes in DirectRT, so it's not a problem for me, but it could be distracting/puzzling if you don't know what's happening.

  4. #4
    Join Date
    Nov 2005

    Thanks so much for sharing your experience with this!


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