ComFprime (F´ Framing) Subtopology — Software Design Document (SDD)

The ComFprime subtopologies implement F´’s lightweight communications stack for framing/deframing bytes on the spacecraft side. There are two variants in the same module:

1. A variant that supplies a Svc::ComStub implementation of Svc.ComInterface and expects to be wired to a Drv::ByteStreamDriverModel (TCP/UDP/UART, etc.), and
2. A variant that expects an external implementation of Svc.ComInterface provided by the deployment.

Both variants provide the standard F´ framer/deframer + router + ComQueue path and are tuned through ComFprimeConfig instance properties.

1. Requirements

2. Design & Core Functions

2.1 Instance Summary (common building blocks)

Two variants: A. “With ComStub”: Subtopology includes Svc::ComStub and exposes ByteStream ports to your driver. B. “With External ComInterface”: Subtopology does not include Svc::ComStub; you provide one in the deployment.

2.2 Required Inputs for Operation

• Rate Groups: Connect a scheduler output to comQueue.run.

• Transport Endpoint:

  • Variant A: Wire ByteStream send/recv between your Drv::ByteStreamDriverModel and the subtopology’s ComStub.
  • Variant B: Provide your own Svc::ComInterface and wire it to the framer/deframer ports in the subtopology.

• Flight-side hookups: Wire the router outputs (commands/files) into your CDH stack (e.g., command dispatcher, file uplink), and feed packet sources (telemetry/events/file downlink) into the ComQueue.

2.3 Limitations

These subtopologies focus on the F´ communications protocol. They do not provide CCSDS framing/deframing nor CDH capabilities.

3. Usage

Below are two usage patterns, one for each variant. Replace identifiers/ports with the exact names in ComFprime.fpp.

3.1 Variant A — ComFprime with Svc::ComStub (expects a ByteStream driver)

topology Flight {
  instance ComFprime.Subtopology

  # (A1) Provide a ByteStreamDriver interface (e.g. Drv.TcpClient)
  instance comDriver: ...

  # (A2) Schedule ComQueue
  connections RateGroups {
    rg.RateGroupMemberOut[0] -> ComFprime.Subtopology.comQueueRun
  }

  # (A3) Wire ByteStream driver <-> ComStub supplied by the subtopology
      comDriver.$recv                            -> ComFprime.Subtopology.drvReceiveIn
      ComFprime.Subtopology.drvReceiveReturnOut  -> comDriver.recvReturnIn
      ComFprime.Subtopology.drvSendOut           -> comDriver.$send
      comDriver.ready                            -> ComFprime.Subtopology.drvConnected
  }
}

[!TIP] ComFprime.Subtopology.commsBufferGetCallee and ComFprime.Subtopology.commsBufferSendIn can be used if the ByteStreamDriver requires buffer management.

3.2 Variant B — ComFprime without Svc::ComStub

topology Flight {
  import ComFprime.FramingSubtopology

  # (B1) Provide your own ComInterface
  instance radio: ...

  # (B2) Schedule ComQueue
  connections RateGroups {
    rg.RateGroupMemberOut[0] -> ComFprime.comQueue.run
  }

  # (B3) Wire your ComStub between the driver and the ComFprime framer/deframer
  connections Link {
        # Framer <-> ComStub (Downlink)
        ComFprime.framer.dataOut -> radio.dataIn
        radio.dataReturnOut    -> ComFprime.framer.dataReturnIn
        radio.comStatusOut     -> ComFprime.framer.comStatusIn

        # ComStub <-> FrameAccumulator (Uplink)
        radio.dataOut -> ComFprime.frameAccumulator.dataIn
        ComFprime.frameAccumulator.dataReturnOut -> radio.dataReturnIn
  }
}

4. Configuration

Configure only the instance properties owned by the ComFprime subtopologies. All knobs live under: Svc/Subtopologies/ComFprime/ComFprimeConfig/ComFprimeConfig.fpp

4.1 Component properties (ComFprimeConfig.fpp)

• Base ID — Base identifier for the subtopologies; instance IDs are offset from this base.
• Queue sizes — Depths for ComQueue and any other active/queued elements defined by the subtopology.
• Stack sizes — Task stack allocations for active components (if any beyond ComQueue).
• Priorities — RTOS priorities for active/queued components as applicable.

4.2 Buffer Manager Bin Configuration

module BuffMgr provides constants for the bins configured for commsBufferManager.

5. Traceability Matrix