Running Pavel Demin's FPGA SDR designs under RP OS image (Ubuntu)

[belotserm]

Can anyone think of reasons why a bit file built off of one of the Pave Demin's SDR block designs would run fine under his Alpine image but would not work properly (no reception) under the Red Pitaya's OS Ubuntu OS image? I assume the device trees should be the same, and the fabric read/write is done via /dev/mem reads/writes which should not differ for different OS kernels.
Thanks

[pavel]

What is the name of the SDR project that you are testing?

[belotserm]

Thanks, Pavel. I've tried sdr_transciever_122_88.

[pavel]

In the past, the sdr_transciever project could run on the OS provided by Red Pitaya. The sdr_transciever_122_88 project is similar and should also work on the SDRlab 122-16 board with the OS provided by Red Pitaya.

The FPGA configuration is only part of the project, you also need to compile and run the C code of the TCP server (sdr-transceiver.c).

[belotserm]

Thanks. I did compile the companion C code using GCC under the RP's Ubuntu before loading the bitfile and launching the application, however it did look like nothing was being received. I had assumed that it was because the communication between the PS and PL got messed up because of how the PS is configured in the sdr_transceiver block design vs. what the Ubuntu image expects, or something like that. I am using a somewhat older revision of the red-pitaya-notes project (which I pulled circa Feb of 2023), and the RP SD card from roughly same timeframe, so perhaps that could be an issue? If you are sure that the transceiver FPGA design should work under RP's Ubuntu on 122-16 board without modifications, then it is likely an operator error on my part. I just wanted to be sure I wasn't trying to do something that the design wasn't meant to be able to do. Should it matter what version of the red-pitaya-notes and what version of the Ubuntu image I'm using?

[pavel]

I am using a somewhat older revision of the red-pitaya-notes project (which I pulled circa Feb of 2023)

This could be why it is not working. There were a lot of changes in the GitHub repository earlier this year and some versions may have been broken.

Should it matter what version of the red-pitaya-notes and what version of the Ubuntu image I'm using?

I would recommend using a release version. It is possible to copy the apps/sdr_transciever_122_88 directory from a release zip file to your system without rebuilding the bitstream file. You will just need to recompile the C code.

[belotserm]

Thanks, I'll try that. As a general note, I notice that in the older Vivado transceiver block design that I'm using, the read and write fifo are mapped to different AXI memory regions, but in the newer version (and in the matching C code) an AXI bridge instantiated in the block design allows writing (TX) and reading (RX) via the same AXI memory space address. Is that something that was partially done to address compatibility issues with Ubuntu kernel, or is it just a more elegant way to do the same thing and has nothing to do with the problem I'm experiencing? I am trying to fully understand how the transceiver design works (both PL and PS) and why it works under one OS vs the other, and not just how to get it to work under one image or another. I thought I kind of did, until now, and that's a bit frustrating to me.

[pavel]

Is that something that was partially done to address compatibility issues with Ubuntu kernel, or is it just a more elegant way to do the same thing and has nothing to do with the problem I'm experiencing?

No, nothing on this list was the goal of the changes that I made earlier this year.

The goal was to improve the performance and portability of my applications between Zynq-7000 with Ethernet interface and Artix-7 with USB interface.

I do not see why the released versions of the SDR transceiver application would not work on the OS provided by Red Pitaya.

[belotserm]

Thank you so much, Pavel, for the explanation. I'll switch to the latest releases of all components and will repeat the test.

[kefopimea]

Have you considered updating to the latest releases of the SDR transceiver application and other components to see if that resolves the issue, and have you checked if there are any specific changes in the AXI memory space addressing between the older and newer versions that might affect compatibility with the Ubuntu kernel?