Raspberry Pi 4 with Mesa 7c81

Could you please help. I have the same setup. Pi4 8gb with 7c81.
I do not understand hostmot2... is it already installed with linuxcnc or how and where do I get it? Does it run in Linuxcnc or in a terminal?
I am brand new with Rpi and Linux. I managed to install linuxcnc 2.8.1 with rt kernel. I am close but stumped!
Thank you

JohnG wrote: Could you please help. I have the same setup. Pi4 8gb with 7c81.
I do not understand hostmot2... is it already installed with linuxcnc or how and where do I get it? Does it run in Linuxcnc or in a terminal?
I am brand new with Rpi and Linux. I managed to install linuxcnc 2.8.1 with rt kernel. I am close but stumped!
Thank you

Hostmot2 is a firmware that runs on the Mesa cards.
There is a matching driver that runs under, and is included with, LinuxCNC, also called Hostmot2. But shortened in HAL to hm2.

But, my main question is, how did you get a Pi4 8GB running with a realtime kernel? I have spent the last few days trying to make kernels and packages that work with that combination after reports from this forum that it didn't work.

Honestly it was luck and a lot of persistence. I followed this guide:

gnipsel.com/linuxcnc/uspace/

This was most helpful but I had to supplement it with info I found here:

github.com/kdoren/linux/releases/tag/5.4.81-rt45

Between those two plus several other searches I managed. It took much cross checking as many of the version numbers had changed since those articles but it worked.
I don’t know what more to tell you but I will be in front of the pi again in about 8 hours and would be happy to give you any info you would like, you just have to tell me how!

Okay. Sounds like everything linuxcnc needs is already installed. So how do I get hostmot2 for the 7c81. Specifically what do I need to type in order to download it then how exactly do I install it on the 7c81? This part makes no sense to me.
Thank you! Happy to communicate directly as well

Ah, right. A 5.x kernel.

Perhaps I have to go that way rather than persist with 4.19.

Everything I read said that things were broken with the 4x.

Please help with the hostmot2 problem!!!

JohnG wrote: HOkay. Sounds like everything linuxcnc needs is already installed. So how do I get hostmot2 for the 7c81. Specifically what do I need to type in order to download it then how exactly do I install it on the 7c81?

It's almost certainly already flashed with the right firmware.

Try this at the terminal:

halrun
loadrt hostmto2
loadrt hm2_rpspi
show pin

If show-pin shows a lot of HAL pins, carry on with the following (I am guessing the names, use tab-completion to get the right ones)

loadrt threads
addf hm2_7c81.0.read thread1
addf hm2_7c81.0.write thread1
start

And at this point you should have a realtime system up and running, and you can set pins high/low etc (setp pinname 1 / setp pinname 0) and read back results (show pin pinname)

When you are happy that it is working.

exit.