Parsing downlinked Data Products

[Mrcoolawesome]

Hello everyone,

I've successfully been able to create and downlink data products with a test project. They get received as a file that looks something like Dp_1234_1234_1234.fdp.

I understand that according to the docs, the ability to process data products is still in development.

My questions are this: when can we expect the ability to process data products via the GDS to be implemented? And, what alternatives, if any, does FPrime have to save, downlink, and process telemetry?

[thomas-bc]

This is already implemented, there is fprime-dp-write ground script that gets installed with fprime-gds, which should be able to decode your data product binary files

Note

fprime-dp-write will be replaced by fprime-dp decode in future releases. See https://fprime.jpl.nasa.gov/devel/docs/how-to/data-products/#ground-decoding

$ fprime-dp-write --help
                                                                                                                                                                                                                                                                                
usage: fprime-dp-write [-h] binFile jsonDict

Data Product Writer.

positional arguments:
  binFile     Data Product Binary file
  jsonDict    JSON Dictionary

options:
  -h, --help  show this help message and exit

Thanks for pointing out the documentation is incomplete. I added that to the scope of the following ticket: #4623

[timcanham]

FYI, DpState.dat is meant to be the on-board file that is used by DpCatalog to keep track the downlinked state of data product files. It wouldn't normally be downlinked. The .fdp files are what are downlinked by DpCatalog via FileDownlink. If you are developing under Linux or something similar that shares a file system with the ground system, they will end up in the same file system, but that's not how it would be realized in flight.

[Mrcoolawesome]

Okay, that makes sense!

I also have one more question. After decoding the data, the JSON file doesn't seem to contain the data I saved and downlinked. According to all the events the data is properly getting written, but I'm not seeing the number that is provided by my component. Am I just not understanding the format of the JSON file correctly? I've provided the JSON file, a screenshot of my events when writing the data products, and the command I'm using to decode the downlinked data products.

JSON File:

  [
    {
      "PacketDescriptor": 5,
      "Id": 268455936,
      "Priority": 0,
      "Seconds": 131177,
      "USeconds": 2169117440,
      "TimeBase": 1706,
      "Context": 34,
      "ProcTypes": 0,
      "UserData": [
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0,
        0
      ],
      "DpState": 0,
      "DataSize": 0,
      "headerHash": 3410230222,
      "dataHash": 0
    }
  ]

Events output:

Command used to decode downlinked data products:
fprime-dp-write DpCat/_DpCat_Dp_268455936_1770080795_00436770.fdp build-artifacts/Li nux/Test/dict/TestTopologyDictionary.json

[thomas-bc]

@Mrcoolawesome can you try the following and let me know how that goes?

pip install -U fprime-gds==4.1.1a4
fprime-dp decode --bin-file <path/to/file.fdp> --dictionary <path/to/dict.json>

Also could you please paste the output of the JSON file as text? Trying to avoid making people download unchecked files. I like to use the details/summary tags for that in markdown.

Example collapsed sections

You can add a header

You can add text within a collapsed section.

You can add an image or a code block, too.

   puts "Hello World"

[thomas-bc]

That being said .fdp being of size 67 bytes sounds like it's empty (default size of header is 63 and default size of trailer(CRC) is 4). So not unexpected that you're not decoding anything.

@Mrcoolawesome we have a brand new How-To: Generate Data Products guide, you may want to take a look at it and see if you are missing a step in generating the DP ?

[Mrcoolawesome]

Sorry for the very late reply. The way I was making the data products was slightly wrong. Once I got it working properly, I used the updated fprime-dp decode command you provided, and I got it working! Thank you very much for the help.