On Fri, Feb 11, 2022 at 8:06 PM Martin Dobbins <[email protected]> wrote:
Hi Gene,
A couple of questions:
I think you started with a rpi3, how does the rpi4 compare?
How do you wire the gpio on the rpi4 to the 7i90HD? any links for cables
etc?
Thanks, Martin
________________________________
On Thursday, February 10, 2022 3:05:57 PM EST Chris Albertson wrote:
Yes, "Mini ITX" is just a shape and a standard for where mounting holes
go but it is a shape that is sold to a cost-sensitive market where low
power ususage and low cost maters. The ITX market is large enough
that mass production drives prices down. So it is a good fit to
hobby-level machine control. I would think a good place to look as
Aliexpress as most of this stuff ships from China at very low cost.
If you are never going to use the computer as an interactive desktop
you could use a Raspberry Pi4. Then use any standard PC notebook to
remote log-in and run the display from the notebook over WiFi. A Pi4
is 1/2 the cost of the cheapest ITX board.
I did this just to see if I could, but the interfacing from the pi to the
lathe IS the cost of the ITX board over and above the 2 gig rpi4. When I
did it, the 7i90HD was suggested, but while it has numerous ways to
configure 72 i/o's, its fpga has no buffering and the 3 50 in i/o sockets
are a PITA to wire uo to, and leave the fpga wide open to being blown by
noise fron ground loops etc. Enter the 7i42TA, the protection magic for
the 7i90HD, but it takes 3 of them. Now I think it would survive the EMP
of a tactical nuke. And because the i/o is there, and now on green
terminal strips that are much easier to wire, I have all sorts of extra
stuff hooked up and running, like a pair of $20 100ppr dials to replace
the missing cranks, speed selectable on a 1,2,5 etc scale from .0001" to
20 thou per click, one per powered axis. All the modular outputs were
used from gpio-0 to the end of the config installed, and I used the gpio
from gpio-71 down for such things as controlling ALL the lathe power with
a couple 40 amp AC SSR's which are switched by the state of F2. I could
go on, but if this lathe ever grows a controllable tool changer like the
EMCO-5 or similar I have buckets of i/o currently unused.
And that rpi4 is running the full desktop raspian buster install. With a
preempt-rt kernel I built on that rpi4. Obviously I shouldn't run FF at
the same time as LCNC as FF plays hell with the latency, but I have
carved air while running FF just to hear it stutter. And it does, but
nothing else seems to bother it that much.
I'm useing the SPI interface version of the mesa file for the 7i90HD and
the 3 wire interface has been bulletproof. No comm errors.
At about 25 watts total for the rpi4, interfacing and 11 watt monitor, I
don't even have a power switch to shut it off. With a small $35 ups and a
20kw generac in the back yard, uptimes are most of a year, till I need to
add something else, I have the i/o left to do it, whatever it might be.
SPI to/from the pi is faster than any other comm method we have, its in
32 bit packets at 41megabaud from pi to mesa card, and 25megabaud coming
back from the mesa card to the pi.
So it wasn't as cheap as I was expecting but the plethora of i/o has had
me considering converting the rest of my machines and saving about 600
watts by shutting down a bunch of old i5 dells, but thats 600 watts of
non-free heat this time of year.
On Thu, Feb 10, 2022 at 5:57 AM andy pugh <[email protected]> wrote:
On Thu, 10 Feb 2022 at 03:04, andrew beck <[email protected]>
wrote:
Its just kinda hard to ship to New Zealand from UK.
Anyone got a oceania source or asia
Mini-itx is just a motherboard standard.
mini-itx.com just happens to be a UK supplier. I often suggest using
their board finder, but then you can hopefully find a local supplier.
--
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, 1912
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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, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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