I can now run EMC2 and it kind of "works"

http://igor.chudov.com/projects/Bridgeport-Series-II-Interact-2-CNC-Mill/15-EMC2-First-Run/
After wiring garage with Ethernet last night I moved on a bit. Worked
until 2am.
I have configured my mill PC to run EMC2 with "ppmc" configuration.
I tried to do a good job, so that all configs are in my CVS source tree, there are shell aliases for everything, etc. The idea is that I want everything to be based on computer settings, so that one computer could possibly run several CNC devices and that I could run EMC2 on several computers. I do not want to hard code everything so that the only thing I run is my Bridgeport Interact from that PC.
Any of my Linux computers for which CNC_ROLE is set via host settings, loads these shell aliases and requires a default machine to be specified.
Just a little planning for the future, so to speak.
Anyway, I created a setup based on 'ppmc', and, lo and behold, it talks to Jon's PPMC board and displays positions. I also wired the speed command of the drive to PPMC's analog output for Y, so that PPMC could drive the Y axis. I verified that it is able to do so, using ppmcdiags program. Based on voltage that I specify, the servo motor spins just fine.
Right now, the only axis able to move and equipped with encoder is Y, and even on it, I have disconnected the timing belt. So it is just a servo motor spinning back and forth. Nothing could possibly crash into anything or pinch any fingers and other body parts. Very safe environment to work on software and on estops and things like that.
Because this is all Linux and X11 based, I can do fun things like ssh to the CNC computer, run EMC2 from ssh, etc. So, I can work on setting this up, without even being in the garage.
The first task of the day, is to disable all estop functionality that is in the default configs, so that I could get the servo motor to move.
I will, of course, re-enable estop when I have that stuff wired properly.
i
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Ignoramus2398 wrote:

http://igor.chudov.com/projects/Bridgeport-Series-II-Interact-2-CNC-Mill/15-EMC2-First-Run/
PCs are cheaper than dirt, and Linux and EMC2 are free. There is no point in trying to have one PC control multiple machines *unless* you are also multitasking the drives and I/O boards between the machines. I do this with one PC and set of drives controlling either CNC plasma or CNC mini mill. If you aren't sharing the drives and I/O boards, it makes little sense to try to share a lousy $99 PC.
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Maybe, but doing things in a configurable way like this, makes for clean, understandable computer settings. I could run two devices off of one PC if I wanted to. I am not saying I should. What I did is I avoided hard coding anything.
i
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http://unitaig.jalling.dk/index.php?id 5 http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?FixingSMIIssues
You can improve reliability and response on your EMC2 system by decreasing hardware latency caused by the System Management Interrupt.
I ran Neils Jalling's hack on my EMC2 system and it decreased jitter by ~ 5% and caused the dreaded "following error" to disappear.
The thermal control hardware continued to work properly on my system after the hack but there are rumored to be systems that will overheat because of thermal routines handled by the SMI.
--Winston
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Thanks. I did not think about it. This is an older PC "designed for Windows 2000" and thus is unlikely to be exposed.
In addition, I close the velocity loop with tachometers (changed my mind again and I am using tachs as of now), so that alone could help with jitter. Even if the CPU is taking a millisecond nap, the servo drives maintain velocity.

If/when I get my mill to work, I want to buy a mini-ITX case with a new mobo, SSD etc and will put it inside the control cabinet. When I look for hardware, I will double check the SMI issue. Maybe I will get AMD hardware.
i
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Ignoramus2398 wrote:

If you want to go compact and in the control cab, look at PC104 form factor systems and some of the other industrial PC variants many of which are not expensive and are specifically designed to run Linux. Try the advertiser index on circuitcellar.com if you need a starting point.
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Well, I picked a few newegg items, if all goes well, I will buy them:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811154091 http://www.newegg.com/Product/Product.aspx?Item=N82E16813121381 http://www.newegg.com/Product/Product.aspx?Item=N82E16819115056 http://www.newegg.com/Product/Product.aspx?Item=N82E16820145184 http://www.newegg.com/Product/Product.aspx?Item=N82E16827135204 http://www.newegg.com/Product/Product.aspx?Item=N82E16820167025
I asked my friend, who is a computer build expert, if they will fit together, but I think that they will.
i
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On 7/14/2010 8:27 AM, Ignoramus2398 wrote:

SMI has been on Intel processors since < Feb. of 1992.
It couldn't hurt to check. See Message 3 under: http://wiki.linuxcnc.org/emcinfo.pl?TroubleShooting
--Winston
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On 7/14/2010 8:27 AM, Ignoramus2398 wrote:
(...)

AMD began supporting SMI before Intel.
__________________________________________________________
Beware! I have not been able to get Linux or EMC2 to run on SATA drives, just PATA. I understand that some folks *have* been able to do this by patching the OS, however.
--Winston
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That is the weirdest thing I heard this week. I do not know what to make of this.
i
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On 7/14/2010 10:42 AM, Ignoramus2398 wrote:

My takeaway: Run the latency test before buying your mobo, if possible. Some configurations just aren't compatible without significant blood sweat and tears.
http://issaris.org/rtai/list.php?offset%&runtime=0&sort_order=machine_id
--Winston
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I do not know how to do that -- no one I know has a Mini-ITX motherboard.
I will ask on the EMC2 forum.
i
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Ignoramus2398 wrote:

Which one do you have? I have several different Mini-ITX boards at work.
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Intel CPU: http://www.newegg.com/Product/Product.aspx?Item=N82E16819115056 Motherboard: http://www.newegg.com/Product/Product.aspx?Item=N82E16813121381
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Ignoramus2398 wrote:

Don't have one of those. Sorry.
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On 7/14/2010 12:27 PM, Ignoramus2398 wrote:
(...)

Please read section 3.1 beginning at "To specifically test the operation of the RealTime kernel, use the kernel latency test supplied with RTAI.":
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?TroubleShooting
It runs on the Linux command line.
As it is running, exercise the system *without running EMC2*. Open windows, edit a file. Pop open a spreadsheet.
Let the program run for say 30 minutes, gathering latency statistics for you.
--Winston
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Winston wrote:

Ubuntu runs just fine on a Mini-ITX EPIA-CN with SATA drives.
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Jim Stewart wrote:

With EMC2 running properly? I think the issue here is not Linux running on it, it is EMC2 running under Linux on it without timing issues that screw up the servo loop.
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On 7/14/2010 12:42 PM, Pete C. wrote:

Excellent!
Yup. I think it's a compatibility issue with the Real Time version of Ubuntu that hosts EMC2.
--Winston
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    O.K. Where does SMI start being used?

    One of the major benefits of tach feedback. I'm glad that you went back to it.
    With tach feedback, your computer only has to be fast enough to tell it when to change velocity, and is not needed to constantly monitor velocity. Worst case is probably when stepper pulses are being generated directly in the software.

    Sounds good.
    Out of curiosity -- do you have a good photo of the belt housing for the Y-axis servo? I'm going to have to make something like it to complete my conversion of my Bridgeport BOSS-3 (started life as steppers run by a LSI-11) to servos. The stepper motor is shorter than the servos, and was mounted directly under the Y-axis leadscrew, with the stepper protruding into a cast-in cavity in the knee. The servo has to be moved to the right of the knee instead of under it, because of the extra length.
    Good Luck,         DoN.
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