Raspberry Pi 4

Bari wrote:

@ gtt38

m.aliexpress.com/item/4000141655235.html is the link to the FPGA board that worked for me.

I didn't see any protection for all the IO's on that board. It gets you lots of gates and unprotected IO, so you'll still need another board to get the IO's out to the real world in a machine environment.

Really easy to create a custom board to protect I/O after..
I wanted to see the ability of a RPI4 to drive 2 FPGA at the same time :

But it's still not working on SPI1 I tried everything possible)

I've found a minimal FPGA board (the smallest i could find on chinese market)

4 layers and only 45x45mm with 3.3 and 1.2 voltage regulators at the back

Hi All,
I got almost of all the issues resolved.
The Latency is reasonably low and the overall load too.
But I have occasional spikes in the read and write tmax of the 7c81.
The SPI clock is set to default and the core isn’t overclocked. The governor is set to performance and fore_turbo is activated. I plotted the clock and is reasonably stable around 500MHz.
I could trace some spikes to the graphics. It spikes when I move or resize a window.
The other spikes are random and couldn’t trace it.
Got anyone similar issues and how you resolved them?
Help is very appreciated.
Thank you,
Denis

Change from timesyncd to ntpd.

Aptget install ntp..

We have seen issues with the timesyncd.

I’ll try it.
Or should I install a RTC to turn off the fake hardware clock altogether?

How bad is the latency?
(servo thread tmax is useful here)

The servo-thread.tmax stays around 30-40% of the servo-thread cycle of 1ms.
But it jumps up to 60-89% during a occasional spike. while resizing a window, open a file or the one i couldn’t trace.

Do you have isolcpus=3 in you kernel command line?

I run 500hz servo thread..

I have isolcpus=1,2,3.

you mean .5 ms or 2ms servo-thread?
I’m not sure if a 2ms servo-thread will work with linear encoders on all axes.