looking for UBUNTU HAL docs

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31 May 2011 11:47 #10220 by alexr
Hello

Can any one help me with finding detailed information about HAL.

Im after information such as how HAL is structured and programed to behave; a manual would be best.

I would prefer to configure graphically (so this type of information is valued more over 1000's of lines of text) but i realize it will be like almost everything else linux based "in console".

you help will be greatly appreciated.

*************************************************************************************************************************

the reason i am looking at HAL is because i would like to build hardware drivers and then move on to make an API so i can dock into emc2.

EVERYONE keeps telling me USB is no good for real-time blah blah blah

I dont give a $h1# im sick of hearing excuses. what happened to innovation?

I have found 3 UBS index controllers online in a week via google of all things! if they can do it for bloated and slow "windows" we can do it for linux even faster and more accurately.

my idea is why reinvent the wheel emc2 works and it does a really good job, i recommend it to every one. but lately i have found myself making excuses for ubuntu.... "its old fashioned ok!" and yeah it doesnt wash with them. me neither.

streamlined instruction (memory) and a deterministic approach should see USB with results same if not better then using the crusty old and no longer supported parallel port.

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31 May 2011 12:21 #10221 by BigJohnT
alexr wrote:

Hello

Can any one help me with finding detailed information about HAL.

Im after information such as how HAL is structured and programed to behave; a manual would be best.


The source code is the manual for EMC...

Good Luck

John

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31 May 2011 12:33 #10222 by andypugh
Why reinvent the wheel?
A good first step would be to persuade USB20RT to compile with the current kernel:
www.rtai.org/RTAICONTRIB/

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27 Sep 2011 19:28 #13475 by wyzarddoc
Alexr;
Please keep me up to date on your quest to get usb working. I have been watching this forum for months and there seems to be a lot of negative feelings about usb. But it has to change
parallel interfaces are going to be a thing of the past
thanks
Doc

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27 Sep 2011 19:43 #13476 by andypugh
wyzarddoc wrote:

I have been watching this forum for months and there seems to be a lot of negative feelings about usb.

I think we would all love USB to be a workable solution for realtime motion control, but it simply isn't designed that way. The very nature of the USB spec means that is can't be realtime.

But it has to change parallel interfaces are going to be a thing of the past

I am amazed they are still available. However do bear in mind that EMC2 also supports PCI, PCI-e and ISA bus cards (OK, that last one is probably even more outdated than the p-port)

wiki.linuxcnc.org/cgi-bin/emcinfo.pl?EMC2_Supported_Hardware

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27 Sep 2011 22:43 #13477 by cncbasher
i fully agree the parrell port is old hat and on it's way out , USB sucks for control of cnc machines , and yes i do know what i'm talking about , and yes i do use USB for CNC .
but until such times as it becomes more reliable and the latency problems are sorted amongst others ,and along with RTAI , EMC apart from using PCI cards or similar , theirs no other option available at present time of writing that i am aware of .

i'd love a hardware ethernet solution to EMC , perhaps a standalone controller perhaps , or embedded linux ( in contrast to a diskless pc )
i'm willing to possibly work on a solution too .

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27 Sep 2011 23:10 #13479 by doug6949
alexr wrote:

I have found 3 UBS index controllers online in a week via google of all things! if they can do it for bloated and slow "windows" we can do it for linux even faster and more accurately.


The fact that USB indexers are available does not mean they meet the standards of reliability established by the emc team.

That windows program (itself a derivative of emc) of which you speak is aimed primarily at the hobby market. Their idea of what's "good enough" will never be accepted in the world of industrial cnc.

As much as the geekiness of emc has been a frustration to me over the years I must commend the developers for their insistence on building a commercially viable control. Nobody else at the DIY level has even come close.

I cannot say whether USB will ever be viable for real time motion control. I can say from experience that nobody in industry has made it work yet. Perhaps there is a reason, because it certainly isn't from lack of effort.

Doug.

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27 Sep 2011 23:37 #13481 by doug6949
cncbasher wrote:

i'd love a hardware ethernet solution to EMC , perhaps a standalone controller perhaps , or embedded linux ( in contrast to a diskless pc ) i'm willing to possibly work on a solution too .


Basher;

I believe ethernet has a better chance than USB. PLC programmers use it almost exclusively for time-critical processes.

Ethernet is presently used by Centroid, Delta Tau, and a few others for CNC. But it is primarily for interface between the HMI (PC) and a dedicated motion control board.

True PC-based trajectory planning seems to be limited to a PCI card interface, Mesa being a good example. A notable exception would be the Pico systems board but then we're back to the LPT.

Doug

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27 Sep 2011 23:38 #13482 by andypugh
One you have probably found which seems popular with Mach3 is the SmoothStepper:
warp9td.com/documentation.htm
I don't actually know how it works, but I suspect it delays transmission of the step pulses for a few 10s of ms, but reports back to Mach3 as if the steps have already gone, allowing it to catch up of there is any glitch in the feed from Mach.
This is fine for Open Loop control with steppers, or step-servos (where the controller doesn't really know where the axes are) but can't be used for closed-loop control.
It is probably fair to say that most of the EMC2 installations out there are running open-loop, but many are full-servo systems.

You might find the Mesa 5i25 an interesting alternative to a parallel port. It looks like a parallel port, but is actually a PCI step/pwm/encoder-whatever card, so the step pulses (etc) are generated on the card rather like the smooth stepper, except it does true realtime (uS latency)

When the 5i25 is $80, I don't see much point in trying to get a SmoothStepper working when it costs twice that.

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27 Sep 2011 23:59 #13483 by cncbasher
totaly agree with you comments Doug,
i believe a ethernet solution would be beneficial to the emc community also , as well as a step in the right direction

as you rightly say , most commercial systems stay clear of USB for very simple reasons,
although i do know and use a few high end commercial USB motion control systems , i think the greatest problem is people to realy understand what a 'real time system is ' and what it's not .
and the differences between windows and Linux operating systems at that level .

hence why 'it works on windows , so it should work on Linux ' option is often quoted or refered to .

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