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.

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1. Requirements

ID	Description	Validation
SVC-COMFPRIME-001	Provide an F´ framer to convert COM buffers into framed packets for downlink using the F Prime format.	Inspection
SVC-COMFPRIME-002	Provide an F´ deframer to parse incoming packets into com buffers for uplink.	Inspection
SVC-COMFPRIME-003	Provide an F´ router to route deframed packets (e.g., commands/files) into the flight software.	Inspection
SVC-COMFPRIME-004	Provide a subtopology variant that supplies Svc::ComStub designed to connect to a ByteStream driver.	Inspection
SVC-COMFPRIME-005	Provide a subtopology variant that expects an external Svc::ComInterface supplied by the deployment.	Inspection
SVC-COMFPRIME-006	Support configurable instance properties (IDs, queue sizes, stack sizes, priorities) via ComFprimeConfig.	Inspection

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2. Design & Core Functions

2.1 Instance Summary (common building blocks)

Instance name	Type (Svc/Drv)	Kind	Purpose (core function)
framer	Svc.FprimeFramer	Passive	Frames fprime data into packets for transport.
deframer	Svc.FprimeDeframer	Passive	Deframes fprime data from incoming packets.
fprimeRouter	Svc.FprimeRouter	Passive	Routes deframed packets (e.g., commands/files) into the flight software.
comQueue	Svc.ComQueue	Active	Queues data for framing (telemetry, events, file, etc.); has Run.
commsBufferManager	Svc.BufferManager	Active	Provides memory allocation to the subtopology.
frameAccumulator	Svc.FrameAccumulator	Passive	Accumulates whole frames before deframing.
comStub	Svc.ComStub	Passive	(Variant A only) Adapts a Drv::ByteStreamDriverModel driver for use as downlink.

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.

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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 {
  import ComFprime.Subtopology

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

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

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

Tip

ComFprime.commsBufferManager can be reused 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
  }
}

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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

Requirement ID	Satisfied by (instance/type)
SVC-COMFPRIME-001	framer — Svc.FprimeFramer
SVC-COMFPRIME-002	deframer — Svc.FprimeDeframer
SVC-COMFPRIME-003	router — Svc.FprimeRouter
SVC-COMFPRIME-004	Subtopology
SVC-COMFPRIME-005	FramingSubtopology
SVC-COMFPRIME-006	comQueue — Svc.ComQueue (run scheduling port)
SVC-COMFPRIME-007	ComFprimeConfig