CaribouLite Pi Zero (1 & 2) Testing and Getting Started Guide

[unixpunk]

Here are my notes about testing on 32-bit Raspbian Lite Bookworm using SoapyRemote / SoapySDRServer while connecting from Ubuntu running CubicSDR on a NUC8i7(Hades VR).

Notes:

• Beware bad performing OTG Ethernets! I have 1 that could only perform at half the combined IQ data rate than the other 2 I tested!
• 2.4ghz on-board wifi is not fast enough to be used with SoapyRemote.
• PoE splitters cause terrible interference which is disappointing (2 of 2 for me).
• Only use UDP. TCP works fine on a Pi Zero 2 but NOT on a Zero (1).
• Anytime you move the CaribouLite and the working SD card/SSD to a different model Pi, you must re-run "./install.sh" and reboot before /dev/smi will become available again.
• These "maxes" are the rate at which I heard no dropouts in FM Stereo audio.
• The Cariboulite seems to continue consuming the same amount of power even after clients disconnect and SoapySDRServer is ended, only running SoapySDRUtil --info causes the Pi to return to normal power consumption until the next client connects.

- Pi Zero (1) - (100Mbps and Gigabit showed the same max)

• • 2MSPS / 2mhz @ CS8
• • 1.3MSPS / 1.3mhz @ CS16

- Pi Zero 2

• • 100Mbps Ethernet prevents operating at 4MSPS / 4mhz @ CS16 (or better) - NEED GIGABIT!
• • Gigabit allows for 4MSPS / 4mhz @ CS32 (nothing CS64 works for me)

Getting started:

1. Raspberry Pi Imager, find the 32-bit Raspbian Lite Bookworm and burn to SD or SSD.
2. sudo apt update; sudo apt upgrade
3. echo dtparam=i2c_vc=on >> /boot/firmware/config.txt
4. echo dtoverlay=spi1-3cs >> /boot/firmware/config.txt
5. sudo sync; sudo reboot
6. sudo apt install git
7. git clone https://github.com/cariboulabs/cariboulite
8. cd cariboulite
9. sed -i 's/THIS_MODULE, //g' driver/smi_stream_dev.c
10. ./install.sh
11. sudo sync; sudo reboot
12. SoapySDRUtil --info; ls -l /dev/smi

[unixpunk]

@alphafox02 FYI in case this helps you, also.

[alphafox02]

Thank you. I’ll have to give it a go. Question for you though. Can you please try on 24.04 Ubuntu for the Pi4. Everything seemed to complete to include the kernel module. But no smi becomes available.

[unixpunk]

Will do. (soon)

[unixpunk]

Not having success; seeing what you're seeing. Not sure if this is "normal". but only "smi" in dmesg is this and no other related messages i can see:

[ 6.106199] smi_stream_dev: loading out-of-tree module taints kernel.
[ 6.107592] smi_stream_dev: module verification failed: signature and/or required key missing - tainting kernel

[alphafox02]

Same, doesn’t make any sense. It’s like the coding.txt is not obeyed or something? I dug all over and it seems like teething is in place, but no smi created. Maybe I need to go file a ubutnu tocket.

[Vinz87]

Hi, those maximum rates are related to remote streaming on a host PC?
What about an onboard processing python or C script? Can it sustain 4 Msps?

At the current state of development, do you think it is possible to have CaribouLite + RPi Zero (1 or 2) and run some processing application written in Python or C at startup for a complete headless setup? Or even to have some GNURadio flowgraph to be deployed and run at startup?
Would these different environments (which I understand all would refer to the SoapySDR APIs) will be capable of transmitting a custom IQ signal? I read TX side was still a issue.

Thanks

[unixpunk]

Correct, when streaming via SoapySDRServer / SoapyRemote. Anything can run at startup, so if you have some code I'd say give it a shot.

RE Maximums - I'd guess that all depends on the CPU usage of the code you're looking to run. SoapySDRServer maxes out CPU on a zero 1 at the max I noted but on a zero 2 it only uses ~30% of a single core at the max. IIRC, Soapy doesn't have much in the way of Tx, but I haven't tried personally. You don't need to use Soapy, you can write your own code to interface and Tx directly AFAIK. HTH