Why does Mach 3 still use parallel port instead of USB?

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  • Black Forest
    Senior Member
    • Jan 2010
    • 8974

    Why does Mach 3 still use parallel port instead of USB?

    Why does Mach stay with parallel port instead of switching to more modern technology? I am sure there is a reason but I can't find it online.
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!
  • John Stevenson
    Senior Member
    • Mar 2001
    • 16177

    #2
    It does.

    It can use both but it's not Mach3 dependant on what breakout board is fitted, there are USB boards out there that work very well.
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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    • adatesman
      Senior Member
      • Jun 2010
      • 1129

      #3
      IIRC the USB port isn't able to maintain stable timing, which Mach needs to operate. The parallel port does, hence using either that or an external USB device that does its own timing, like SmoothStepper or KFlop.

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      • BigJohnT
        Senior Member
        • Sep 2012
        • 489

        #4
        BF I sent a PM to you

        John
        My Web Site

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        • EVguru
          Senior Member
          • Dec 2008
          • 1986

          #5
          If you install it under a 64 bit operating system then the parallel port is no longer an option, you have to use a motion control board.

          Some people are very upset over this. They seem to feel they have a right to use an affordable piece of software on the latest operating system and have it support an obsolete piece of hardware.
          Paul Compton
          www.morini-mania.co.uk
          http://www.youtube.com/user/EVguru

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          • lazlo
            Senior Member
            • Jun 2006
            • 15631

            #6
            Originally posted by adatesman View Post
            IIRC the USB port isn't able to maintain stable timing, which Mach needs to operate. The parallel port does, hence using either that or an external USB device that does its own timing, like SmoothStepper or KFlop.
            That's correct. USB is an arbitrated, packet-based interface, and completely non-deterministic.

            Mach bit-bangs the parallel port to generate pulses: it schedules a high priority Windows processes that writes to the raw parallel port. Hopefully, Windows services that interrupt handler often enough that you drive the stepper
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • Black_Moons
              Senior Member
              • Aug 2009
              • 9096

              #7
              Pertty much, to use USB you need something smart enough to take g-code (or something similar) and do all the PID loop(if any)/ pulse generation internaly. Takes a little more skill to program a microcontroller to pull that off then it does a PC with infinate gobs of computing power.
              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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              • MrFluffy
                Senior Member
                • Jan 2006
                • 1475

                #8
                What lazlo said, its easy to bitbang pins on a parallel port via asm at low level, but usb is a lot more abstract and more difficult to time.

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                • Evan
                  Senior Member
                  • May 2003
                  • 41977

                  #9
                  You can bit bang the USB port using a USB to serial converter but the hardware timing is only accurate to a few milliseconds at best. That's good enough to run a stepper at a 100 steps per second or less but that would be a very slow CNC machine. It is however plenty good enough to run a telescope drive.
                  Free software for calculating bolt circles and similar: Click Here

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                  • John Stevenson
                    Senior Member
                    • Mar 2001
                    • 16177

                    #10
                    Just use one of these:-



                    Does 4 axis and spindle speed control. 16 inputs, 200KHZ speed
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                    Comment

                    • Black Forest
                      Senior Member
                      • Jan 2010
                      • 8974

                      #11
                      OK John, What is that and where can it be bought?
                      Location: The Black Forest in Germany

                      How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                      • EVguru
                        Senior Member
                        • Dec 2008
                        • 1986

                        #12
                        Sometimes people forget to look for clues and use a search engine;

                        Google + 'leafboy77' = http://leafboy77.com/index.php/en/
                        Paul Compton
                        www.morini-mania.co.uk
                        http://www.youtube.com/user/EVguru

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                        • EVguru
                          Senior Member
                          • Dec 2008
                          • 1986

                          #13
                          And with a little bit more work; http://www.automationtechnologiesinc...breakout-board
                          Paul Compton
                          www.morini-mania.co.uk
                          http://www.youtube.com/user/EVguru

                          Comment

                          • DFMiller
                            Senior Member
                            • Jan 2005
                            • 1488

                            #14
                            Yes John, tell us which one that is.
                            I would suggest looking at Ethernet as a better option.
                            USB is not galvanically isolated and can suffer from noise issues. Case in point the Smoothstepper USB in some cases just would not work reliabilly where the Parallel Port would. The Ethernet version of the same product does not seem to have same issue. It's a noise issue. Spent many weeks in my router install before I binned the Smoothstepper.
                            Dave

                            Comment

                            • DFMiller
                              Senior Member
                              • Jan 2005
                              • 1488

                              #15
                              Thanks Paul for the link,
                              Looking at the schematic very skeptical on its robustness.
                              Google does not report much, at least one person is having issues and not much about people's successes.
                              Dave

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