Raspberry PI4 and different MESA Cards

Hi All,

I built a hobby  (just for fun) 3 axis minimilling machine with steppers on the axes. I experienced that the GPIO is slow in some cases and misses a step when moving fast. This could be solved by limiting the speed and it was also mentioned in the descriptions that there could be problems. After reducing the speed limit, the Raspberry PI 4 works very well. I use a spiral with a different thread pitch on the Z axis than on the X and Y axes. On Z, you can feel that the Z axis is slow. What I found in various forums is that some external e.g. is recommended for such cases. Use of external cards (for eg. MESA cards). And in this regard, I have some questions to which I could not find a clear answer.

Is there a table somewhere that compares (advantages, disadvantages, total prices, etc.) the different versions for the Raspberry PI 4? for e.g. GPIO, various MESA cards etc.. I have read many things, but I still don't know which one would be the best for me? It is described in many places that there can be speed (performance) problems with GPIO, I have experienced this myself. However, I could not find a comparison, e.g. between the MESA card with Ethernet or other host interfaces? If I understand the MESA webshop correctly, should I choose from "Anything I/O Daughter Cards"? And the possible cards are 7C80 ($249), 7C81 ($89), 7I76E ($199), 7I96 ($149)? Which of these is the most appropriate? My understanding at the moment is that the ethernet cards are better considering that I can use it with more than just a Raspberry PI if I have to replace the CPU?

Best regards,
Gabor
 

I cant answer much about mesa card but in regards to the rpi gpio speed these may help you

Make a backup of your sd card first.

To help with latency one can disable wifi and BT
run the following cmd in terminal
sudo nano /boot/config.txt

Edit the file to have the below lines
dtoverlay=disable-wifi
dtoverlay=disable-bt

Also you can disable audio by adding # in front of dtparam=audio=on

so if you do the above 3 things it should give you a bit more speed. you can also do an overclock of the rpi but you need to add a good cooler and fan.
Results may vary.
add the following lines
arm_freq=2000
gpu_freq=800
over_voltage=6
force_turbo=1
gpu_mem=512

Then another set of things to change are the following
sudo nano /boot/cmdline.txt
add the following as one line then save and exit
quiet splash lapic noxsave acpi_osi= isolcpus=1,2,3 idle=poll acpi_irq_nobalance noirqbalance vmalloc=32MB clocksource=acpi_pm net.ifnames=0