Reporting for failed CRCs on commands

[keck-in-space]

Hello,

It looks like if an F Prime executable detects a failed CRC, it is silently discarded:

https://github.com/nasa/fprime/blob/devel/Svc/FrameAccumulator/FrameDetector/FprimeFrameDetector.cpp#L91

We would like for this to be an Event message or otherwise reported via telemetry channels. Is this possible?

[thomas-bc]

Yes it's very much possible. Feel free to open a feature request for this. The same can be said of the TcFramerDetector for the CCSDS TC protocol.
Note this only applies if using the FrameAccumulator to reassemble frames. If direct connection ComAdapter (delivering full frames i.e. not a bytestream) -> Deframer, the deframers do emit an event on CRC mismatch.

[keck-in-space]

Thank you very much. I'm a bit confused on the second point. In what scenario would we be using the direct connection that would emit an event on CRC mismatch?

[thomas-bc]

Sorry if I wasn't clear. I was simply making a note that you can plug your ComInterface component (e.g. radio manager component, ComStub, etc.) directly into a Deframer. The reason FrameAccumulator is here by default is because we usually default to TCP comms. Because TCP is a stream of bytes, you need to detect/reassemble frames from that stream of bytes on the receiver side. That's what FrameAccumulator does. In the case of UDP, or if a radio component yields full frames, there's no detection to be done so FrameAccumulator can be dropped and it'll function just the same.

[keck-in-space]

Thanks again! I think I follow. We're using UART, so we would need the FrameAccumulator to reassemble the frames from bytes on the receiver side. I suppose i'll open a feature request. It would be nice to see if commands are failing CRC and if so, how many bytes are discarded as we test out interfaces.