MODEP and Raspbery Pi 4

Hi, the Linux kernel developers are doing their best to keep the user space software forward and backwards compatible in regards to kernel versions, and they seem to be succeeding quite well. So as long as the kernel you’re using supports the Raspberry Pi hardware version you want to use, it should be good to go.

Some useful links for kernel building, as well as how the last Patchbox OS kernel was built:

@Giedrius thank you very much!
I’ve patched and compiled the kernel 5.6, copied it to a fresh Patchbox sd card,
as described at the page you have linked above, and it works!
I cannot say anything about stability because it’s as fresh as my pisound (arrived today).
So far - I’ll attach the pisound tomorrow.

1 Like

Please let us know how it goes! I assume you’re using RPi4 8GB?

Yes, I’m using a RPI4 8GB.
After flashing Patchbox I did
apt-get updtae && apt get -y dist-upgrade
to get Patchbox running a kernel version 5 and newest firmware already
before manually updating to the patched kernel 5.6.
I did this because the first time I tried to manually updating to 5.6
I did it with a current not "rpi-update"ed Patchbox image with kernel 4 and it failed to boot.
After the “rpi-update” the USB ports were starting to work
and after manually copying the patched 5.6 kernel they are still working.

The pisound is running but the HDMI output stopped working with connection the pisound.

Do you mean video or audio output over HDMI?

HDMI video is not working. I haven’t tested HDMI audio.
But maybe it’s about the thickness of the case regarding the length of the plug.

In my experience, Raspberry Pi’s are not good at detecting hot-plugged HDMI devices too, so make sure you have it connected before powering on the system.

Running a test patch with 75% CPU usage it’s getting hot:

vcgencmd measure_temp

Thus indeed a fan is needed.

75% CPU, really? Is your patch super intense or big? My RPi 4 stays at 3-10% CPU even with lots of modules (~15).

I just installed Patchbox from the image to my SD card, then used patchbox tool to get the MODEM module.

I made a test patch with this CPU usage. It is important for performances to have a stable system at ± 75% CPU usage. Throttling is pure horror for audio live performances.
I want to use Camomille or pdlv2 for running pd patches for spectral processing.
I think it is easy to run out of CPU power.
If I would need just 10% of the RPI 4 I would happily stick with the RPI 3.
The RPI 4 is “famous” for introducing a heat/cooling problem to the RPI.
Thus the ideal solution would be blokas developing and selling a solution like a new case with a fan or a different cooling system like the one posted here: (;

It’s in german but the pictures are talking.

Until there is a ready made solution from blokas it is required to tinker.
So for me today the combination of RPI 4 and pisound is for the studio, desktop or any save environment where I can use it without a case but not for the floor board or any rough environments.