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ComFprime Subtopology

docs/reference/system-functional/subtopology-com-fprime.md

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ComFprime Subtopology

References

Overview

The ComFprime subtopology packages the F Prime protocol communication stack as a reusable building block. It provides the complete data path for downlink (framing outgoing packets) and uplink (deframing incoming data and routing packets to their destinations). This subtopology uses the lightweight F Prime framing protocol, which is suitable for development, testing, and missions that do not require CCSDS-standard framing.

Two variants are available:

  1. With ComStub — Includes a ComStub communication adapter and expects to be connected to a byte stream driver (TCP, UDP, UART). This is the simplest option for most deployments.
  2. With External ComInterface — Does not include a communication adapter; the deployment provides its own implementation (e.g., a radio driver). This variant is used when the communication hardware requires a custom adapter.

Topology Diagram

Downlink Path

Uplink Path

Included Components

  • F Prime Framer — Frames outgoing packets using the F Prime protocol (start word, size, payload, CRC).
  • F Prime Deframer — Validates and extracts payloads from incoming F Prime protocol frames.
  • F Prime Router — Routes deframed packets to their destination (commands to the command dispatcher, file packets to file uplink).
  • Communication Queue — Queues outgoing data (telemetry, events, file packets) and sends it to the framer. Supports priority-based ordering.
  • Frame Accumulator — Collects incoming byte stream data and assembles complete frames for the deframer.
  • Buffer Manager — Provides buffer allocation for the communication path.
  • ComStub (variant A only) — Adapts a byte stream driver to the communication interface.

Configuration

  • Base IDs, queue sizes, stack sizes, priorities, and CPU affinities are configurable via ComFprimeConfig.
  • The Communication Queue depth and priority levels are configurable.

Required Inputs

  • A rate group connection to drive the Communication Queue's send cycle.
  • A byte stream driver (variant A) or custom ComInterface implementation (variant B).
  • Connections from telemetry, event, and file downlink sources to the Communication Queue.
  • Connections from the router's outputs to the command dispatcher and file uplink.