> > On Sat, 9 Mar 2019 at 16:31, John Dammeyer <[email protected]>
> wrote:
> > > How does a simple test like:
> > >
> > > if (COOLANT_SWITCH == 1) PUMP1 = 1; else PUMP1 = 0;
> > >
> > > become abstracted through the HAL into the actual low level?
> >
> > Skipping all the other stuff that I can't answer....
> >
> > In HAL that is "net some_signal an_input => an_output"
> > A concrete example:
> >
> > net coolant_on iocontrol.0.coolant-flood => hm2_5i35.0.7i76.0.1.gpi0-00-out
> >
> That should be .0. above, not ,0. :)
The Xylotex HAL file for the BBB MachineKit has:
# connect DB25-11 to X home and min limit
net home-x bb_gpio.p8.in-10 => axis.0.home-sw-in axis.0.neg-lim-sw-in
We have "net" as opposed to "setp" and "newsig" which also show up in the hal
file. No idea what .net tells us.
Next there's "home-x" which I'm guessing is the name of the signal and at some
level somewhere deep in the bowels of the application just before a step pulse
is issued and the step would move in the direction of the home switch the
program checks to see if where home-x points is ON.
Now "home-x" is really just a label - like a word in a dictionary and the
definition would be, in the C language, a pointer to structure that eventually
maps to the actual physical hardware.
The other side of the => is an application specific data structure. A
different non-CNC program that was using this pin as a door closed sensor
wouldn't have axis.0.home-sw-in axis.0.neg-lim-sw-in.
It might have room.0.entrance-sw-in
Anyway for LinuxCNC the "axis" is the overall structure of all axis on the
machine.
The ".0" identifies that it's the first axis which is the X axis and the
".home-sw" is pretty self-evident.
The second space delimited identifier on the line "axis.0.neg-lim-sw-in" tells
us this switch is also used for the X axis negative direction limit switch.
If compiled into C code it would ultimately look something like this when the
home switch is checked.
if (axis.0.home-sw-in) {
// home reached so decelerate if homing.
}
if (axis.0.neg-lim-sw-in) {
// negative limit reached so stop motion now.
}
At the compiled level the axis.0.home-sw-in holds the address of
bb_gpio.p8.in-10 and the real code hidden behind the dressing is more like this
in both cases.
If (*bb_gpio.p8.in-10)
}
But I don't think LinuxCNC nor MachineKit compiles this into C code. So how is
this indirection used?
I wouldn't even know where to start looking for it in the source code for
LinuxCNC.
Thanks
John Dammeyer
http://www.autoartisans.com
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > � George Fitch, Atlanta Constitution Newspaper, 1916
> >
> >
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>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
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>
>
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