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Thread: USB to Parallel port??

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    USB to Parallel port??

    Has anyone used a USB Parallel port to run CNC on a Tri-Power?

    Would this work? My computer doesnt have a parallel port.

    Similar Threads:


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    Registered pminmo's Avatar
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    A usb converter doesn't work. If you want to use usb you need to purchase a smooth stepper or similar.

    Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
    Vist my websites - http://pminmo.com & http://millpcbs.com


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    I just recently put a "smooth stepper" on my Shoptask Elderado machine using a Camtronics controller. I had upgraded computers and it didn't have the parallel port. I tried the ad on ones but they simply didn't work. The "smooth stepper" worked as advertised and is working great.
    smooth stepper



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    A little tech here:

    The USB connection is a serial one. You have two data wires, a power and a ground. The parallel port is an 8 bit parallel, with separate grounds and discrete pins for paper out etc.

    Most 'dumb' devices are OK with a USB parallel port.. things like PDAs, and printers. Most printers now a days do not used the descrete pins, they talk to the driver over the data bits.

    The stepper controllers NEED those descrete pins and such. If you were to conenct a break out box to a USB parallel adapter you would see some pins never light.. since they have no way to be triggered over the USB cable.

    There ARE some USB cables that have a chip that can decode the USB data and set descrete pins. There is a specific chip that is used, and it does work... for the life of me I cannot remember what it is.

    I just went through this with an old laser printer and a Vista laptop. The $2 E-bay USB adapters failed, but the the one finally worked. It was about $20.

    Last edited by pfarber; 06-12-2009 at 03:24 PM.


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    Registered pminmo's Avatar
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    Quote Originally Posted by pfarber View Post
    There ARE some USB cables that have a chip that can decode the USB data and set descrete pins. There is a specific chip that is used, and it does work... for the life of me I cannot remember what it is.
    There are NO, let me repeat, NO USB to parallel port converters that can handle the step pulse timing needed by MACH3, EMC, Turbocnc or cncpro. It has nothing to do with the discrete pins, it's strictly a real time timing issue of pulse generation.

    If you want to use usb, you need a smooth stepper or equivalent.

    Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
    Vist my websites - http://pminmo.com & http://millpcbs.com


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    I think we agree that that there are no < $100 solutions. There are PICs with USB connections that can take the data stream from USB and convert it to parallel.

    The part that I quoted does just that.. its a low end solution but that's what a 5 minute Google search gets you.

    The smooth stepper gizmo is the same thing after I looked at it.

    This is really only a laptop issue. Parallel post carts are readily available for $15 and drivers for Windows are available. Every PC still comes with a few PCI slots. For the cost of the smooth stepper you can buy a Pentium 3 and use that.



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    If your laptop has an expansion port, PCCard, pcmcia, pc card express (or whatever the new one is called) there exists parallel port adapters for those, those may get you going with your laptop if that is the only pc you have to use. Ive not tried them, but its worth considering.



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    There are all kinds of things that make a laptop less than suitable for shop CNC control not the least of which is the subject of this thread. MACH turns a PC into a controller not just a PC running another application. The PC that runs your machine needs to be considered dedicated to that task alone. It's not there to run CAD or CAM or to edit drawings or surf the web. When you set it up, put it in a protected enclosure with it's keyboard and monitor at the operator and forget it's a Windows PC. If you must do file creation (CAM) sitting at the machine use you laptop and network it to the control computer. I actually prefer to do that in the AC'd office and not in the shop. Even if you get the parallel port thing sorted out with MACH, there are other challenges running MACH on a laptop.

    USB communication is bursty (uneven datastream), serial (one bit at a time) and limited in noise immunity. It cannot provide a low jitter set of timing pulses. The solution is to buffer up the pulses and move them out in a constant pulse stream. That takes horsepower (cost) and disconnects the control software from the actual position of the machine. I love USB for connecting external devices to a PC. My keyboard is USB. So is my printer and even a backup external drive. None of those depend on a direct steady data stream. You can throw enough hardware and development into most anything and make it work but that is not the true definition of engineering.

    You can buy a refurbished HP 2.4 or 2.8 GHZ computer with a keyboard and mouse and with XP Pro loaded. It has a parallel port, serial port, USB ports and 3 open PCI slots. Last one I bought came in a foam shipping box and was $129.00 plus $25 freight. All I had to do was load MACH3 and it was a Controller. At that price I keep a spare around for any of the 4 tables we have running in production.


    TOM Caudle
    www.CandCNC.com



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    I've been doing some research today on possible solutions for the parallel port dilemma of late.

    Torchhead makes a good point, desktop computers really are the way to go if you have the space. They are a lot cheaper and offer more options. An LCD monitor can add quite a bit to the price if you are trying to save a little on space. However, CRT monitors can be had for practically free if space is not and issue. Also, if a desktop doesn't come with a parallel port, both PCI and PCIe Parallel Port cards can be had for less than $20, either on newegg or ebay.

    But, if you are really tight on space and prefer your computer take up less space than your CNC machine, a laptop may be the only option. If you have an older laptop, then most likely it has a parallel port. If not you can get a PCMCIA Cardbus Parallel port card again for about $20 at newegg. If you have a newer laptop that does not have a parallel port or a cardbus slot, but has a ExpressCard slot, then until recently the options have been expensive ($100 or more). There are plenty of expresscard parallel port cards out there for $20, but they utilize the USB lines in the expresscard socket, so they are the same as any USB to parallel adapter and wont work. These are called USB based expresscard adapters. For an expresscard parallel port card to work with CNC, it needs to be a PCIe based expresscard adapter. It needs to use the PCI Express pins for the interface instead of the USB pins. Until recently this option also cost around $100. Today on ebay I found an expresscard parallel port card for under $35 based off the
    OXPCIe952 bridge chip. Details can be found here: http://www.plxtech.com/products/uart/oxpcie952

    The cool thing about it is that it also has serial port capabilities so you can have a single expresscard adapter with both a serial and parallel port. Here's an ebay search for the cards with this chip: http://shop.ebay.com/?_from=R40&_trk..._nkw=OXPCIe952
    So far I have only seen one seller who sells these. I ordered one from them today, so when I get it I'll test it out and see if it works.

    More Info:
    http://en.wikipedia.org/wiki/PC_Card
    http://en.wikipedia.org/wiki/Expresscard
    http://www.synchrotech.com/products-...dapter_00.html



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    Unfortunately the parallel ports on many laptops don't put out a clean enough pulse stream for motor control. Your mileage might vary though.



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    I've read about the dirty pulse stream in quite a few places including I believe in the Mach 2/3 manuals. I've also read about a lot of people having success. I'm curious if it may be possible to disable some of the power saving features on the laptop that it seams are the culprit, either in the bios or in windows. I'm curious if there is a connection between those who have success or failure using a laptop and the type of breakout board, drivers, etc they are using. I have a PMDX-122 breakout board and I noticed PMDX has added a note/warning about this very topic to their breakout board product pages in red partially bolded text. http://www.pmdx.com/PMDX-122
    I am using Gecko 203V drives.
    I am also curious if a PCIe based expresscard parallel port card would solve this problem since it is semi-external not being incorporated into the laptop design, possibly giving immunity to internal hardware oriented voltage tweaking. The card would be using the PCI express bus just as a PCI express parallel port card in a desktop would. I think this is covering new ground here. I've never read about anyone actually trying this and reporting results. It only cost $35 so it's worth a try. If it doesn't work with CNC, then the ports should be useful for another application.

    http://en.wikipedia.org/wiki/PCI_Express



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    Quote Originally Posted by ryanhathy View Post
    I've read about the dirty pulse stream in quite a few places including I believe in the Mach 2/3 manuals. I've also read about a lot of people having success. I'm curious if it may be possible to disable some of the power saving features on the laptop that it seams are the culprit, either in the bios or in windows. I'm curious if there is a connection between those who have success or failure using a laptop and the type of breakout board, drivers, etc they are using. I have a PMDX-122 breakout board and I noticed PMDX has added a note/warning about this very topic to their breakout board product pages in red partially bolded text. http://www.pmdx.com/PMDX-122
    I am using Gecko 203V drives.
    I am also curious if a PCIe based expresscard parallel port card would solve this problem since it is semi-external not being incorporated into the laptop design, possibly giving immunity to internal hardware oriented voltage tweaking. The card would be using the PCI express bus just as a PCI express parallel port card in a desktop would. I think this is covering new ground here. I've never read about anyone actually trying this and reporting results. It only cost $35 so it's worth a try. If it doesn't work with CNC, then the ports should be useful for another application.

    http://en.wikipedia.org/wiki/PCI_Express
    The problem with laptop based pulse generation is the energy saving features of the laptop tend to start and stop the pulses that are being generated by the cpu. That being said there are plenty of people who put in the time to make it work. Do a search and you will fund that turning all of the power saving features off, setting it for a desktop computer in windows, run a program designed to keep the cpu at full speed and a host of other things can make it work. I think I have read that some older laptops will work as is.
    At work they are putting in all new computers and getting rid of the dell c600?? laptops. I have read that they work well with the onboard p-ports. I will try to pick up one to see if it works.

    Mike

    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.


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