RE: New project...PCI based servo control board

["Craig Edwards" <cedwards-at-ceinetworks.com>]

Likewise, I've not seem much use for A/Ds.  Aside from a tach channel,
(which I don't think EMC uses?), I don't know what they would be used for.
Maybe some sort of auxiliary positioning or velocity feedback?  I was also
thinking 4 channels... But six would be "nice".  We'll have see where we end
up in pin count.

-Craig
-----Original Message-----
From: emc-at-nist.gov [emc-at-nist.gov] On Behalf Of Dave Engvall
Sent: Wednesday, March 26, 2003 3:31 PM
To: Multiple recipients of list
Subject: Re: New project...PCI based servo control board



Hi all,
Just to put in my two cents worth. Exclusive of the hexapod people most of
us can get along with 4 channels of dac/encoders. As far as I can tell the
A/D functions of the stg card don't get much use. DIO probably should be an
add-on (daughter board?) in 32 bit or so increments. Yes, I know...that
limits us to 3 axes and a spindle drive or external  spindle and A | B | C.
Now I'll leave the real work to the people that know how to do it. IOW --
low cost would be nice.

Dave Engvall

----- Original Message -----
From: "Craig Edwards" <cedwards-at-ceinetworks.com>
To: "Multiple recipients of list" <emc-at-nist.gov>
Sent: Wednesday, March 26, 2003 11:42 AM
Subject: RE: New project...PCI based servo control board


>
> Hi John,
>
> Sounds like we are thinking along the same lines...  And yes, I'm
certainly
> open to collaboration.  At this stage, I'm envisioning a single PCI 
> card, with an architecture that is very tightly coupled to the primary 
> CPU. That's why I've mostly considered the PCI bus, despite the 
> complexity and cost drawbacks. It has low latency if properly 
> implemented and is well supported by all OS's Most definitely FPGA 
> based, because I'm sure we
won't
> get it "right" the first time, at least with regard to feature set. 
> Actually, I guess I'm thinking that if we can get the initial board 
> design completed with just a basic set of functions implemented, it 
> could "grow" over time to support more advanced features.  Initially I 
> was thinking of primarily including the functionality of the Servo to 
> Go ISA board, with stepper support being something for the future.  
> But as Ray says... Twist
my
> arm...I agree we should try to get as many inputs as possible.
>
> As you probably know, the PCI bus (and associated drivers) are fairly 
> complex, at least if one wants to do a full implementation.  Even 32 
> bit, 33MHz target only VHDL code for a FPGA instantiation is pretty 
> pricey, but I'm working on some options.  If we can afford a large 
> enough FPGA, there will be plenty of room for stepper pulse generators 
> and GP I/O.  As you pointed out, there a large number of trade offs to 
> be made with regard to how many features we try to include on single 
> board, but that's the fun of
a
> project like this.  I'm not very familiar with Jon Elson's designs, 
> but
I'll
> have a look at them.  I think it's fair to say I'm pretty firmly in 
> the "single board" camp, as I really want a solution that is tightly 
> coupled
to
> the motherboard. But having said that.. I guess we could consider
"daughter"
> cards....:)
>
> I'll try to have some sort of preliminary board spec to talk about at
NAMES,
> capturing as much of everyone's input as I can.  I need to better
understand
> what the programmers would like to see in way of interfaces.  I'm 
> thinking that some sort of block I/O, reading or writing to multiple 
> registers with one transaction would be preferred... But maybe single 
> register is access fine.  Anyway LOTS to talk about, I hope we can 
> hook up at NAMES.
>
> Best regards
>
> Craig Edwards
>
> -----Original Message-----
> From: emc-at-nist.gov [emc-at-nist.gov] On Behalf Of 
> jmkasunich-at-ra.rockwell.com
> Sent: Wednesday, March 26, 2003 9:42 AM
> To: Multiple recipients of list
> Subject: RE:New project...PCI based servo control board
>
>
>
>
>
> Craig Edwards wrote:
>
> > Actually, I started on a project around a year to
> > define and build a PCI based servo control board,
>
> > I've tried to solicit some feedback for requirements
> > on a couple of other forums, but most were/are
> > interested in a more "distributed" sort of solution
>
> > Anyway, I'm thinking this group might be more interested
> > in this project; if so, I would like to try to attend
> > NAMES just to meet some of you and to better understand requirements 
> > for the "ideal" servo / encoder interface board that could be easily 
> > used by EMC.
>
> I'm interested, both as a potential customer and a
> potential contributer.  Are you aware of Jon Elson's universal stepper 
> controller and PPMC board set? The stepper contoller has 4 high speed 
> pulse generators and 4 encoder counters, as well as some general I/O.
> The PPMC set is more modular, and includes an encoder,
> input board, analog output board (for analog servo amps),
> and generic digital I/O.
>
> One of the problems that face any hardware solution is
> the wide range of requirements.  Some folks have analog
> servo systems, and need analog outputs with encoder
> feedback.  Others are using Gecko style step-and-direction servos, and
need
> pulse train output, with optional encoder feedback.  Others are using 
> steppers, and simply need pulse outputs.  Then there are all the 
> secondary
> functions: Jog wheels need an encoder input.  Lathe spindles also need and
> encoder input, with an index pulse for threading. Rigid tapping on a mill
> also needs a spindle encoder. Variable speed spindle drives need an analog
> output, even if the rest of the axis drives are step and direction. And
> every system needs some amount of digital inputs and outputs, for limit
> switches, e-stops, tool changers, spindle and coolant control, and so on.
>
> For example, consider my project.  I am trying to CNC a Shoptask 
> 3-in-1 machine.  I want to do a first class job, with support for 
> threading, variable speed spindle drive, etc.  My requirements are:
>
> Three main axis (X, Y, Z), with Gecko microstepping drives. One aux 
> axis (rotary table or index head), also Gecko stepper. Each of
these
> axis needs a pulse generator, and probably a pulse counter (unless the 
> generator is open-loop accurate). Each axis also needs at least one 
> and up to three inputs for limit and home switches.  I also need an 
> encoder input for a jog wheel, and an encoder input (with index pulse) 
> for the lathe spindle.  I will be using a VFD for the spindle drive, 
> so I need start, stop, forward/reverse, and speed reference signals 
> for the VFD, as well as two signals to control contactors to connect 
> either the mill or lathe
motor
> to the VFD output.  Finally, the Shoptask millhead can be raised or
lowered
> (in lieu of a knee), and at a minimum I want an encoder to tell the
control
> where the head is at.  Control of the head with up and down outputs 
> would
be
> better.  (It is driven by a reversible gearmotor, and never moves 
> during a
> cut.)  I haven't thought too much about coolant yet, but I certainly want
to
> be able to add it.
>
> So there is my list.  I'd like to collect as much input from others as 
> possible - what combination of encoders, analog outputs, pulse 
> generators, digital I/O, etc., are needed for different types of 
> projects?
>
> Does anyone have any creative thoughts on how to mix and match these 
> functions?  I know of two basic approaches, and Jon Elson's products 
> demonstrate both.  First, you can go modular.  Jon did that with the 
> PPMC line, where one board has 4 analog outputs, one has 4 encoder 
> counters, one has digital I/O, and so on.  On the plus side, you can
> mix and match the stuff you need.  On the minus side, the
> cost is high because you need a number of individual boards
> as well as a motherboard.  Jon's Universal Stepper controller takes the
> other approach.  It has a fixed set of functions in one FPGA, on one
board.
> That means a lower cost, but if you need one more encoder, or 
> whatever, there is no simple expansion path (other than adding another 
> whole board).
>
> I'd like to discuss options, and possibly come up with an open 
> hardware design.  I am willing to do circuit design, board layout, 
> etc.  Craig also seems willing to work in this area.  Maybe we can 
> come up with a design that is both flexible like a modular system, and 
> cheap like a fixed system...
>
> John Kasunich
>
>
>
>
>
>
>
>
>
>
>