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4 - FPGA CARDS

PC CONNECTION
Mesa offers FPGA main cards with a variety of different PC connection types.  First decision is which connection method is used as this will depend on your computer hardware:

    • Ethernet
        ◦ Ethernet cable from the LCNC computer (PC or Raspberry Pi) to the Mesa FPGA card
        ◦ No additional hardware is required
        ◦ Network switches will interfere with the Mesa ethernet connection.  If the host computer only has one ethernet port, you must use a different port for internet connections (i.e. USB WiFi)
    • SPI
        ◦ Raspberry Pi plugs directly in to a Mesa motherboard via the Pi’s GPIO pins
            ▪ 7C80 & 7C81 cards
            ▪ NOTE - rpi 5 is not supported for direct plug-in (SPI) as of 2/2024
    • Plug-N-Go kits
        ◦ A Mesa card is plugged in to a PC’s internal PCI or PCIE slot, and a second card, external to the PC, is plugged in to the PCI card.
        ◦ The second card is connected to outside hardware (drives, IO components, etc.)

There are other host computer-to-Mesa connection methods available, but those are less frequently selected by novice LCNC users and will not be discussed in this guide.

ONBOARD IO
Some FPGA cards have onboard IO and/or drive outputs, and some don't.  As an example, compare a 7i76EU with a 7i92TH.  They are both FPGA main cards and both do approximately the same thing, but the 7i76EU has onboard IO connectors and the 7i92TH doesn’t

The onboard IO type is an ‘all-in-one’ arrangement with screw terminal connections for drives as well as analog & digital inputs and outputs.  This type also has one (or two) expansion connectors for use with daughter cards.

The other type of FPGA card has no onboard drive/IO screw terminal connections, but it does have connectors for use with daughter cards.  Examples of this type are the 7i80DB or 7i92TH.

Plug-N-Go kits are, essentially, a ‘no-onboard IO’ FPGA card coupled with an external drive and/or IO daughter card which has screw terminals.

As far as the novice LCNC user is concerned, there is no performance difference between an ‘all-in-one’ FPGA card and an equivalent no-IO FPGA card combined with suitable daughter card(s).

Which type of card to select is primarily dependent on which, if any, daughter cards are desired, as well as packaging/mounting restrictions.  A very large ‘all-in-one’ card, such as a 7i95T, may be harder to fit in a tight enclosure than a 7i92TH with remote-mounted daughter cards.

On the other hand, if you have the space an all-in-one FPGA card can be tidy as there are no inter-card cables or multiple mounts to deal with.

EXPANSION PORTS
FPGA cards can also be categorized by which expansion port type is used to connect daughter cards:

    • 'All-in-one' FPGA cards have one or two 26-pin expansion connectors.
    • No onboard IO FPGA cards may have
        ◦ Two (or more) 26-pin connectors, or
        ◦ Two (or more) DB25 connectors, or
        ◦ A combination of 26-pin and DB25, or
        ◦ Two (or more) 50-pin IDC connectors

The type of expansion port provided by an FPGA main card is very important to understand because while a DB25 daughter card can be adapted to a 26-pin FPGA port with a special cable, 50-pin daughter cards cannot be plugged in to DB25/26-pin connectors (and vice-versa).

Simplified, an FPGA’s expansion port(s) must be compatible with the daughter card(s) connection type.

 

Thank you so much it worked ! I used :
7zz x image_pi5_rt.zip
command in Ubuntu terminal to extract

Donno wrote:

When i download the image and extract it i get error, third attempt.

 

The pi5 image from the site is the one with video driver problems.

 

I checked.
he file must be decompressed with 7zip (www.7-zip.org/) and the image can be written to SD with Balena Etcher (etcher.balena.io/).

As you can see from the photo, LinuCNC works and you can select the screen resolution.

 


 

While looking at options to add a few isolated outputs to my 7i92th. I recalled a post by PCW " here " saying the SSR module is for transformer isolation. Sounds interesting.

After reading the hostmot2 SSR section of the docs and taking a close look at my 7i96s as a reference. I think I have a grasp on how this is being done. However I do have a few questions.

 I assume the line driver / buffer protects the fpga pins and can better drive the primary coil. Is a inverted output line driver / buffer required or would a non inverted IC work the same? 

 How critical is capacitor value? I was unsure how to properly calculate the values for the primary and secondary transformer capacitors.

Here is what I came up with for adding a few SSR outputs to my 7i92th (heavily 7i96s influenced). I wanted to get some feedback before routing the board traces and ordering a pcb. Some components differ from what is on my 7i96s, I am just trying to use what I have on hand. I can however make changes if I have made poor component selections.



Thank you in advance for your advice.

When i download the image and extract it i get error, third attempt.

 

The pi5 image from the site is the one with video driver problems.
 

rodw wrote:

Very nice. Try monitors from greentouch. www.greentouch.com.cn/?list_9/
Can you list specifications for your spindle and x,y,z stages?

The specific motor and drive models of X, Y, Z and Spindle are indicated in the Project Procedure List.
Thank you for your recommendation. I'll buy one and try it next time.

I didn't use Beckhoff IO devise in this project, so I don't really clean up the license, or do you mean the ethercat licence? I didn't check this specifically. This project is only for internal use of the company, not for sale, so I'm not sure whether it violates Beckhoff licence.

andypugh wrote:

Have you managed to work around the strange Beckhoff licence?

I don't think there is an issue here for software. If a machine design is used to make a machine  to sell  for profit, you need to have a company and register for a free license with tthe Ethercat Technology Group

Very nice. Try monitors from greentouch. www.greentouch.com.cn/?list_9/
Can you list specifications for your spindle and x,y,z stages?

Have you managed to work around the strange Beckhoff licence?

PROJECT VLOG: space.bilibili.com/341589947/channel/col...ondetail?sid=1918828
GitHub: github.com/rabin-HE/OPENCNC-J

• Introduction
  • This is an open-source integration project based on Linuxcnc. Its aim is to facilitate electrical engineers in using a combination of Linuxcnc + EtherCAT with CIA402 protocol + Raspberry Pi (or X86 - Debian).
    

I think I've finally licked it.

I hooked the TMC5041 clock up to the clock on the Raspberry Pi. It didn't detect any improvement. So then I created a test program that essentially runs the servo loop like LinuxCNC, calling the same code just outside LinuxCNC. The problem was still there only not as bad.

I then started commenting out an non-essential TMC5041 register reads. And like magic the position jumps stopped. So in the end my driver loop was too slow. Reminds me of the old saying, when you hear hoofbeats think horses not zebras.

It took me so long to find the issue because the halscope graph didn't look like there was a delay. I expected the position number to flatten out before jumping. Maybe this a case of the graphing library helping too much. I also thought the SPI reads would be much faster than they actually seem to be.

My plan going forward is to have separate functions for issuing the commands to the TMC5041 and reading data back from it.

Hi,
I want to use Raspberry PI 4 + LinuxCNC-RIO (Tangoboard) with SPI connection.
How can I enable SPI (using the IO pins) with the LinuxCNC image?
How can I disable the automatic screen lock?

Thanks,
-- Itai

 

I think this one has been answered on GitHub, but for future reference. If you have a configuration file (some examples are available here ), lets say 5a-75b_v8.0_i24o32.json, you can compile this file with:
When the compilation is successful, a new directory with the compiled firmware will be created. The name of this directory is equal to the name of the configuration file. The .svf-file required for flashing can be found in the gateware sub-directory. For this example you can change the directory and then flash the firmware with the following commands:
The above command is valid when you use a RaspberryPi in combination with the HUB75HAT as a programmer. If you have a different programmer, such as the FT232R, you have to provide the name of the configuration file for OpenOCD, i.e.:
These commands will flash the firmware only in this session. When you power-cycle the FPGA, the previous program will be loaded again. To make the firmware permanent, one has to flash the NAND-flash on the board. One can use the --permanent flag:

Hurray!!!! After 8 days I've managed to get a version of Raspberry Pi OS, the prempt-rt patch, and Linuxcnc and linuuxcnc-dev on my 3B......Was picking at it daily while trying to read and absorb the documentation on it and Remora.....

So I guess the next step is to install the Remora stuff on Linuxcnc?

How's those cheap as chips boards coming along that you've been working on? Are they ready for a thick headed pensioner to make a version yet ? And what do I order as far as one of these "pill" things?

Cheers from sunny Canada,
Lewis