Custom RFNoC Block to add metadata results in no packets sent to UHD

[zminot]

Issue Description

I've been trying for a bit now to add a custom RFNoC block for the x410 that simply just overwrites the metadata field in the incoming CHDR packet to a specific value (in the shared code, it's 0xDEADBEEFDEADC0DE for simplicity). I integrated a similar testing schema as the addsub testing bench so I'm pretty sure the block functions correctly.

However, when actually adding the add_metadata block to a core yml file and creating the image, UHD sends an error of overflow (the "O" to stdout) when running the example rx_samples_to_file. When looking at Wireshark, I simply receive no packets at all from the x410.

I have been following the directions stated in the RFNoC UHD 4.0 Guide.

On a similar note, on page 14 of the RFNoC specification, it says that "The framework will provide the ability for the user logic to extract and insert metadata into a packet...", but I haven't found any such tool as of yet. If there already the ability to do so in the PL of the FPGA, then I can likely just use that instead of adding this.

Here is a GitHub Gist with the block files and the image core yml file I used to generate the file. I know GitHub issues aren't really for debugging custom additions, but since I believe the custom code is correct and the RFNoC specification says there is an ability to do so, I thought to make this an issue. Let me know if there is anything else I should add!

Setup Details

Ubuntu 20.04.4 LTS 64-bit UHD 56f3aab (was just the latest commit at the time of installation) USRP x410 Connection to the device is via the Ethernet port.

Expected Behavior

Adding the custom RFNoC block to add metadata will send packets with the added metadata to the host machine.

Actual Behaviour

No packets are sent at all, and UHD gives the message of overflow ("O").

Steps to reproduce the problem

Add the custom RFNoC block shared in the gist as directed within the RFNoC UHD 4.0 Guide. Make sure all CMakeList files are updated with the new files if necessary. To run the tests, it should be make rfnoc_block_add_metadata_tb To generate the image core, it should be make x410_200_rfnoc_image_core_metadata after adding the yml file to icores. Then load the image core to the fpga using uhd_image_loader and the appropriate arguments as described in the RFNoC UHD 4/0 Guide.

Additional Information

Maybe there is something I'm not testing for?

[wordimont]

Hi @zminot. First, quick disclaimer. The metadata feature isn't fully supported in UHD. Because the software doesn't fully support it yet, it hasn't received much testing. That being said, I'm not aware of a reason why you'd be having this issue.

[zminot]

Should be okay from my front, I only want to deal with metadata from within the FPGA RFNoC pipeline and don't have a need for it within the UHD app.

If there is any way to monitor the signals within the FPGA during a recv call, I can definitely do so and analyze that too.