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BigJohnT wrote:
I did not propose removing feature, I just said that may be all things that there are some features may not be available with USB, If you need that feature, then you don't use USB.
If you don't need these features like most milling machine users, then you could have USB as an option. Having some communication channel better than step pulses from printer port could also open some use cases like easier to use BLDC servos.

Kate

Kate

You must see how this would not interest most of the current developers...
It completely eliminates the most interesting features of EMC and stunts growth of any new ones (using USB)
To do anything interesting you must put the controller in the USB box.
That is completely a different philosophy.
Everything that makes EMC great is because the controller is in the PC.

Now if you or anyone else wants to produce code that does just what you said - limits features but uses USB - as another option
I'm sure we would look at it. But don't expect a lot of developers joining in though I'm sure they will answer any questions and offer ideas.

If you could come up with code that uses USB (or anything else) and still leaves the the PC as the controller thats completely different.
No one has ever come up with code. I'm thinking there is a reason!

As far as using BLDC servos, there are already step and direction drives that make this easy.

So in short other then USB is familiar and very common - there is no advantage to use it and one big reason not to (not realtime).

kate wrote:
Yes. We have the "bldc" HAL component which accepts Hall sensor or encoder input, and generates 3-phase PWM demands for power modules or driver boards. I think all current users are using either the Mesa 7i39 board (3-phase, 3-wire PWM) or the 8i20 (digital angle/current demand) but it ought to be able to drive a power stage such as an IRAMS module or a cluster of MOSFETs directly too.

www.linuxcnc.org/docview/2.5/html/man/man9/bldc.9.html

cmorley wrote:
I understand this, all we do FOSS that we feel interesting to ourselves. Some ones are more interested as example threading,
i would like to see 5 axis mill that I could make about finished quality surfaces for composite molds

When i look result of poll www.linuxcnc.org/component/option,com_po...s/id,2/lang,english/
I am not wrong saying that around 90% uses emc2 for some kind of milling machine,plasma, laser etc and are would
benefit USB interface. It is fact that printer port is going to be extinct, it starts be very difficult
to find any more compact PC mother boards that even have the printer port and for good reason because this
port has not been used by printer any more least last decade. Having big ugly desktop PC in shop with full
of metal chips is not practical.

I succeeded to buy couple of VIA based compact boxes with printer port but then I needed to compile all
kernel, RTAI and EMC from live CD install just because these old ones does not have LAPIC ...
doing this hack is already big obstacle to basic user as addition to find motherboard with printer port.

For this 90% of use cases, it would be much, mush easier just buy a some compact box and attach
interface via USB. I understand that many developers see their interesting challenges elsewhere than
normal user.

That's different if you want just a mill or stunts. I understand that having all under same PC
allows many stunts that may be very interesting but most of users are not so interested about
these stunts. I don't blame any developers abut being interested about these stunts, FOSS
must be fun and the stunts are part of this fun. I am happy having great software.

I understand, i just tried to say that USB interface would benefit 90% of users and there is no technical reason why it could not work.

I don't like call it as "not realtime", as definition realtime just means that system has guaranteed response time what ever it is, in most cases
1ms loop is considered realtime. There are certain tasks where 1ms loop is not enough as is emc2 50us loop cases like stepgen or servo.

I don't see that either open loop case, stepper motors or moving 50us closed servo loop to USB box means that PC is not a controller. How it differs in case of
"analog" brushed DC servo amplifier case, servo amplifier has it's internal 50us 100us or what ever fast control loops inside, same thing in step/dir BLDC servo controllers.

Least some M$ Win based CNC software are using USB, so it is not so uncommon.

May be we are just looking this from different viewpoint, I see that USB has great advantage for most of basic users but has disadvantage that it does
not allow some stunts that needs cross linked fast control loops. I am not proposing removal of any features needed to implement these stunts.

I really hope that no one feels this offending, I am very happy to have this great software and big thanks to all of it'd developers.
There is just different viewpoints coming from different needs.

Kate

kate wrote:
Which is why EMC2 supports PCI, PCI-e, and ISA, modbus ie, other interfaces that are suitable for the task at hand.

Just because the parallel port is obsolete is no reason to automatically jump to its successor printer port.
The parallel port is an easy and convenient way to control simple machines, but EMC2 has always supported more suitable interfaces too.

Incidentally, rigid tapping is a nice feature to have on a milling machine, it isn't only lathes that benefit from threading capability. (though you can use an auto-reversing tapping head instead, if you can afford one)

kate wrote:No, over and over we state that there ARE technical reasons why USB will not work. It is because
USB does not allow round trip operations to a single device in a frame, and that it is a deep
hardware feature of the USB chips, and therefore can't be overridden by software.
What you are asking for is to turn EMC into Mach, and the developers have a number of reasons
not to do so. If you want to run open-loop stepper drives via software step generation, Mach
certainly works for the general case. Why do we need to duplicate what they already do?Intel just released the D525MW, a compact Atom board with a parallel port on the rear panel, even
more convenient that the D510MO with the parport on a header. The D525MW also has a
PCI (not PCIe) slot where you can plug in an additional parallel port if needed. A complete
system can be built for about $200, if you just want the board to put into a control cabinet,
you can do it even cheaper.

So, the argument that the parallel port is unobtainable is just not true.

Jon