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Depends where you live in this big old world. I've seen 7i92 clones boards on AliExpress that are the same as the original 7i92. To get one Down Under is more or less 80 - 100 AUD, which is more or less the postage alone.
Now here's comes what would be done hypocrisy on my part. Whilst I have built a 7c81 / 7i90 clone using a Spartan 6 Dev board and some custom PCBs, I wouldn't buy a clone from AliExpress, due to the Mesa cards I've bought being solid and reliable and PCW being so supportive to all and the help he gave with my endeavours. I know it sounds strange.
I feel these boards and people asking for support may be a topic that could be divisive.

I'd either go for mesa or riocore, both types will run on a Spartan 6.

Riocore is pretty good in that it has quite a few mesa doesn't support, has also port for a number of different FGPAs. The only issue is that it needs rebuilding of the driver for each time you change to fpga config. RIO also has a Ethernet plugin that uses a w5500, as of yet no plugin for the Ethernet chip used on the Mesa boards.

Mesa is very very mature, one driver is all that is required for changes to fpga if you keep to the standard mesa set of modules. SmartSerial is a big plus as well.

I built a 7c81/7i90 clone using a spartan 6 dev board and some custom PCBs, mesa & riocore firmware both ran fine on it.

Keep up the good work.

Thank you very much for your suggestions.
Seems like there is indeed a lot of fine tuning or trial and error necessary.

Even with limits set to 99999, this happens; and on one system, I also got the probe error, although my „probe flipflop“ was held in reset.

So far, my first working setup >2.8.4 is the RPi/7c81 combo,
but with that working, I hope to find some time to learn more about your proposals for the Ethernet solution.


Thx,
AS

Kudos go out to all who made this possible:  
60000+ probes for now, during the last 24 hours, with an RPi5, 7c81 and the brand new 2.9.7.  
Zero issues, so far.    \o/

While probing, this thing now also runs a VNC server in the background,  
I am connected via VPN; it’s streaming music and also downloading a random  
10GB image file in a web browser.  

Pretty good latency too. Comparable to a decent RTAI setup, imho.  

Still some extra steps, as described here,  
  forum.linuxcnc.org/49-basic-configuratio...rol-is-choppy#332726  
and this "xset -r“ drives me crazy, bc I have to use the keyboard until I managed to get the handwheel working.

 

RIO now actually consists of two projects:

1. Configuration front end with HAL/INI generator

2. FPGA gateware generator


In Rio, there are now two ways to use a Mesa cards:

1. with RIO firmware/gateware (FPGA gateware generator)

Unfortunately, only those with an SPI interface. I will try again to build something that works with the MII chips when I get the chance, but it may take a while.

2. Original hm2 firmware (HAL/INI generator)
Still being tested. At the moment, only the 7c81 is supported, as I have this at home. Next will
be the 7i92.
This should actually support all cards, but in order to configure them correctly in the flow tool, you have to enter all pin positions into a file, which is simple but time-consuming.


I have already ordered a 7i92 clone from China.

The biggest issue would be a driver for the ethernet chip.
The mesa firmware uses a softcore (think very basic CPU) and that runs assembly language program to do all the hard lifting.
Ollie's original aim was to not have a softcore so there was virtually no jitter. I pretty sure I have this right.
To get this done I really think Ollie would need a 7i92 to do this.
The 7c81 was a simple task as it already had SPI, the 7i90 would be easy as well.
The thing with the Spartan 6 it's picky regarding which pin is the system clock and which is the SPI clock. I had trouble with the 7c81 clone I was working as the pin used for the system clock was different on the dev board I was using to the original mesa one.

Now that is not to say Ollie could not do it. If he could that would be pretty awesome as I have a couple of the Ethernet chips the 7i92 uses. Microchip offers free samples of their products.

Once you're used to it it's fairly easy. No programming skills are required.....well to modify pin functions, the actual VHDL stuff is different.

This is the info I used to start building bit files for some clone 7c81 I worked on.
tom-itx.no-ip.biz:81/~webpage/emc/xilinx...14_install_index.php

Thanks, all.

In general, I like the Ethernet solution, especially because it comes with a built-in galvanic isolation.
What I dislike is, that this more or less rules out all notebook solutions, bc I need a network connection.

From what I experienced, but maybe it was all just bad luck, is that all internal WIFI connections do not work,
except for a couple of devices with a PCMCIA wireless card. I did not try every possible combination, but also
USB to Ethernet adapters seem to have a severe impact on latency.

Is my 7i91 too old maybe?
Of course, I set up everything with the help of pncconf and used the default settings wherever possible.

I had latency (network) test running for days without issues; I programmed a Python script to let the A/B tables
rotate for hours flawlessly; but five minutes of probing and error - one real longer milling job and joint error.
I spent hours in front of the HAL scope, just to catch this magic moment. I even had a camera recording it.
Nothing was caught in flagranti.

I now, just for fun, developed a USB to SPI MCU board and started to mod some of the LinuxCNC SPI
code for the 7c81. Not sure yet if isochronous transfer is possible or interrupt transfer would clog everything.
This would be my preferred (notebook) solution.


Which computers are you using for the 7i91? Whenever I browse through all of this here, I only see
10+ years old systems at work (like tommylight’s Thinkpad collection, hehe).
What about a top modern one?

And just to make sure, you all mean PREEMPT-RT, right? Not RTAI. 

Ok you're telling me not to use a kernel that I have practical experience and have not had a single crash or anything similar. Neither have any users reported any crashes. I think an uptime of 39 days and being able to start Linuxcnc at anytime during that period with no crashes, latency errors or any other such issues proves to me that the kernel is solid and stable.
Before using it on the mill, I had been using to test some Mesa clones one based on a 7c81 and another more less based on the 7i92 design. I've also tested Ollie's riocore system, on the same 7c81 clone hardware early this year, before Oliie got his hands on a genuine Mesa 7c81 that he has made riocore formware for.
Could you point me to any papers, references or any such peer reviewed articles explaining why the 16k page kernel is broken by design.

So this time I will stand by my choices for the RPi5. Unless of course you can provide hard evidence as requested above.

Even this page says to config 2711 for RPi4 to RPi3 and 2712 for RPi5.
www.raspberrypi.com/documentation/computers/linux_kernel.html

Danke, das ist schon mal ein Ansatz! 

Im Moment sehe ich da zwei Möglichkeiten:
- Raspberry Pi 5 + ein Parallel Hat von byte2bot
byte2bot.com/products/parallel-port-rasp...gak8F2DJq1o7WoFK2x-g

Verstehe ich das richtig, dass damit die Erzeugung der Signale die an meine Fräse gesendet werden im Raspberry stattfindet, und somit von der Systemauslastung, Latenz, etc.. abhängt?

- Raspberry Pi 5 + MESA 7C81
Während hier die Signale in/von der Mesa Karte erzeugt werden?

In beiden Fällen muss ich die .hal Dateien so anpassen dass die korrekten Pins angesprochen werden, das ist mir klar.

Aber funktioniert das grundsätzlich so, oder liege ich daneben?

Mesa 7c81 over w5500 - Ethernet on RPI4 with qtdragon_hd (3.3Khz loop)

www.youtube.com/shorts/agf3f0MJxv4

LinuxCNC-RIO - Mesa 7c81 - 7.14 KHz loop - 4x400W AC-Servos

www.youtube.com/shorts/DAJdqbjLjDQ

As long as network latency isn't impacted theoretically it may work.
The RPi will suffer somewhat if you require the use of a base thread for some input requirement. Personally I think an SPI for simplicity a 7c81, which is simple to replicate using off the shelf Spartan 6 Dev boards, maybe a better option for IO.

7C81 RPI FPGA board
1.5" RPI GPIO cable for 7C80 and 7C81
DIN Tray 107MM X 102MMFor 7C81, 7I94, 7I94T

The Raspberry PI, standoffs, and fans are NOT included.

Works perfectly. Selling because I bought a MASSO 3G Touch.

$75 plus shipping.
 
 

 

Some Testest with the Mesa 7c81 and 400W Servos:

www.youtube.com/shorts/KLijHrYiQXw

Board: eusurplus.com/index.php?route=product/product&product_id=131 + 5Axis-BOB
Servos: www.amazon.de/dp/B0DM5V6BZ2
Spindle: Huanyang VFD via Modbus