Re: parallel port finally obsolete?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@...> wrote:

>
> scyvt wrote:
> > Having not been so closely following developments in the last year or so, I was wondering if such a black box had been perfected, and if motion control software had been adapted to it. From the responses so far, I have to conclude that the answer current is: still in development, by no means standardized; and furthermore not everybody sees the need - despite the disappearance of parallel ports from new computers.
> >
> Well, not sure what you are asking here. I have been making a stepper
> controller
> since 2002, with an FPGA and parallel port communications.
> So, it has been out there for a whole decade! It does not more the entire
> motion control task out the the external device, just the job of putting out
> step pulses. So, it needs the computer to be in "real time" control with
> it to watch position and keep feeding it new velocities. Moving everything
> out to the external hardware sounds good at first, but it puts a layer
> between
> the motion control and the user. That means delay, and possibly an
> interruption
> of the communication.
>
> What I DO NOT UNDERSTAND at all is why people are constantly trying
> to find a "better way", when this problem has been solved. Mach works
> quite well for a number of folks, and to my way of thinking LinuxCNC solves
> the problem completely, professionally, and still leaves great
> flexibility to
> adapt the system for specific applications.
>
> So, I have been making three different "black boxes", all dating back to
> 2002
> to 2004, for step/direction drives, analog servos and digital servos.
> It is not
> "still under development" but a production product. Mesa uses a fairly
> similar scheme but a different packaging arrangement, and they have
> also been making these for a number of years.
>
> Jon
>

Jon:

As a long time and respected member of CCED I am glad you posted. Having watched this market evolve and go from dedicated high dollar controllers to low cost PC based controls, gives you perspective that is grounded in logic. Some early approaches (before Art figured out how to make a Windows computer put out HF pulse streams) were it have a "special" card that plugged into the PC and ran the drivers. It worked because the parallel data never had to be first translated to serial then back to parallel to get multi-channel control. Even today there are cards like Galia (SP) cards that still converse on the PC buss but loop the feedback through the electronics on the card.

There seems to be a trend to go back to the future and move the controller back out of the PC (where it can be done cheaply) and move back to dedicated controllers. It is human nature to think there is always a better way to do things but sometimes "elegance" gets translated as "better".

There has been a lot of work done over at EMC2 (aka LinuxCNC) and you have always been a leader. You never tried to force builders into using EMC and in fact have been open about the fact it may not be a good choice for the casual non-technical builder.

The hand wringing and gnashing of teeth over the "death" of the parallel port has been going on for years. There was a rumor that XP (and then WIN 7) would not even support parallel ports...which were both false.

The lowly Parallel Port does have it's limitations. It can't generate much past 65,000 pps unless you have a really fast PC .I know EMC is much "closer" to the ports and Linux is WAY more efficient than Windows on resources but those limitations start to show up on more complex servo based machines. (although it escapes me what benefit a machine with .001 accuracy gets from having a resolution in the 4000 to 10,000 steps per rev, and with gearing motion in micros per step. On the up side it was free on computers for years and still available for about $14.00 as am expansion card.

There are lots of solutions. (unlike 8 years ago) In some ways it just confuses the market.

CCED has always been a place where builders can come and ask questions, get reasonable answers and not be flogged with sales posts. Contributors like yourself that have the experience and insight
are valuable.

Tom Caudle
owner-moderator