fprime_cfs_reference: A cFS System Using F Prime cFS Applications

This repository contains a minimal cFS system that demonstrates the use of cFS applications built with F Prime. This demonstration includes the application:

1. fprime_app: A simple demonstration app showing how to construct cFS applications using F Prime

The system also includes the standard cFS lab apps:

• sch_lab: publishes the 1 Hz tick that drives the F Prime application's rate groups
• ci_lab: command ingest, receiving cFS command packets over UDP (port 1234)
• to_lab: telemetry output, forwarding subscribed software bus telemetry over UDP (port 2234)
• raw_commander: native cFS app that every 10 s (SCH_LAB wakeup 0x18A4) sends command 0x18A0 (function code 1) with a random 1-32 byte payload to the F Prime app and checks the echo on telemetry 0x08A1, reporting match / mismatch / timeout through EVS
• raw_commanded: native cFS app that answers the F Prime app's command 0x18A2 (function code 1) by echoing the payload on telemetry 0x08A3, reporting receipt and rejected commands through EVS

ci_lab and to_lab are the system's only path between the software bus and the ground, used by every ground system, one at a time (to_lab forwards to the single destination last named in a TO_LAB enable-output command, which the cfs-lab plugin sends on connect and after each quiet interval): the F Prime GDS (through the cfs-lab communication and cfs framing plugins of the fprime_cfs library), the cFS GroundSystem, and any other. This path is plain UDP with no authentication or integrity protection: isolated lab and bench networks only. to_lab is subscribed to the F Prime downlink messages (telemetry 0x0801, events 0x0802, files 0x0803, data products 0x0805, packetized telemetry 0x0820; this reference produces only events and packetized telemetry, the others are subscribed so a project adding channel, file or data-product downlink needs no table change) in fprime_cfs_reference_defs/tables/cpu1_to_lab_sub.c. F Prime events additionally reach cFS EVS through FPrimeCfs.EvsMirror.

flowchart LR
    fprime_app(("fprime_app")) --- Bus[cFS Messaging Bus]
    sch_lab(("sch_lab")) --- Bus
    ci_lab(("ci_lab")) --- Bus
    to_lab(("to_lab")) --- Bus
    gds["F Prime GDS / cFS GroundSystem"] -- "UDP :1234" --> ci_lab
    to_lab -- "UDP :2234" --> gds

Loading

Setup

Clone the repository and initialize the submodules:

git clone --recurse-submodules https://github.com/fprime-community/fprime_cfs_reference.git

Set up the python virtual environment and install the required dependencies:

python3 -m venv fprime-venv
source fprime-venv/bin/activate
pip install -r requirements.txt

You should be ready to prepare and build the reference system.

Tip

Always activate the virtual environment using source fprime-venv/bin/activate before running any of the following commands.

Building the Reference

This reference is built using the standard cFS build system. The first step is to prepare the build:

make SIMULATION=native prep

Once this build is prepared, build and install the reference system:

make
make install

Running the Reference

Note

The F Prime application's rate groups are driven by a 1 Hz tick message (command MID 0x1890, APID 0x090) published by the sch_lab scheduler app included in this system. The schedule is configured in fprime_cfs_reference_defs/tables/cpu1_sch_lab_table.c.

The build is installed in build-artifacts/exe/cpu1/. You can run the reference system using the following command:

cd build-artifacts/exe/cpu1/
./core-cpu1

Raw cFS inter-application echo

raw_commander / raw_commanded and the F Prime EchoResponder / EchoCommander components exchange native cFS command and telemetry packets whose payloads are opaque bytes (not F Prime serialized data) and never reach the ground. Watch the EVS events on the core-cpu1 console (RAW_COMMANDER ... matched, RAW_COMMANDED: received echo command) and the F Prime events / counting channels (FPrimeApp.echoResponder.*, FPrimeApp.echoCommander.*) in the GDS; test/int/test_raw_cfs_echo.py checks both. Warning events report mismatches, timeouts and rejected commands.

Running the F Prime GDS

The F Prime GDS commands through ci_lab and receives telemetry from to_lab using the cfs-lab communication plugin and cfs framing plugin installed by the fprime_cfs Python package (./libs/fprime_cfs/python, part of requirements.txt). The plugin sends the TO_LAB enable-output command itself, so the GDS can be started before or after the cFS system:

fprime-gds --communication-selection cfs-lab --framing-selection cfs \
    --dictionary ./build-artifacts/exe/Linux/fprime_app/dict/*Dictionary.json -n

Pass --cfs-address/--telemetry-destination when cFS runs on another host: the address of the cFS host, and the IPv4 dotted quad of the GDS host as seen from cFS (TO_LAB takes no hostnames), respectively.

Running the cFS GroundSystem

The cFS GroundSystem can command and monitor the system directly through ci_lab and to_lab using the fprime-cfs tooling from the fprime_cfs library (its GUI needs the groundsystem extra: pip install './libs/fprime_cfs/python[groundsystem]'):

fprime-cfs --dictionary ./build-artifacts/exe/Linux/fprime_app/dict/*Dictionary.json \
    --ground-system-dir tools/cFS-GroundSystem \
    --deployment build-artifacts/exe/cpu1 --app build-artifacts/exe/cpu1/core-cpu1

Enjoy!