exn-gs

Ground Segment TUI + daemon for STM32 CCSDS packets.

System Overview

The exn-gs project provides a modular ground segment for communicating with STM32-based satellite systems using CCSDS packets over PUS (Packet Utilization Standard).

Architecture

graph TD
    UI[exn_gsui - Terminal UI] -- TCP/IPC:7777 --> Daemon[exn_gsd - GS Daemon]
    CTL[exn_gsdctl - Control Tool] -- TCP/IPC:7777 --> Daemon
    Daemon -- Serial / TCP --> SIM[stm32_sim - Satellite Simulator]
    Daemon -- Serial --> HW[Physical Hardware]
    
    subgraph "Ground Segment"
        Daemon
        UI
        CTL
    end

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Components

• exn_gsd: The central daemon. It handles:
  • Uplink/Downlink via Serial or TCP.
  • CCSDS framing and PUS packet decoding.
  • State management and logging.
  • IPC server for UI and control tools.
• exn_gsui: A terminal-based user interface using FTXUI. Provides real-time TC/TM monitoring.
• exn_gsdctl: A command-line utility to send commands to the daemon without the UI.
• stm32_sim: A simulator that emulates a satellite's communication interface (sending telemetry, receiving commands).

Build

Dependencies

• Boost.System, Boost.Asio
• CMake >= 3.20
• A C++17 compiler (GCC/Clang)
• FTXUI (fetched automatically via CMake)

sudo apt update
sudo apt install -y libboost-dev libboost-system-dev

Compilation

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j

Usage

1. Start the Simulator

The simulator listens for a connection from the daemon.

./build/sim/stm32_sim --listen 127.0.0.1:9000

2. Start the Daemon

Configure the daemon to talk to the simulator (or a real serial port) and listen for GS clients.

# Connect to simulator via TCP
./build/daemon/exn_gsd --listen 127.0.0.1:7777 --port tcp://127.0.0.1:9000

# OR connect to real hardware via Serial
./build/daemon/exn_gsd --listen 127.0.0.1:7777 --port /dev/ttyACM0 --baud 115200

3. Start the UI

./build/ui/exn_gsui --connect 127.0.0.1:7777

UI Controls:

• c: Open command bar.
• h: Toggle help overlay.
• q: Quit.
• Esc: Close command bar or help.

4. Use the Control Tool

You can send commands directly to the daemon:

# Send a ping command
./build/tools/gsdctl/exn_gsdctl ping

# Send raw hex bytes (Command frame)
./build/tools/gsdctl/exn_gsdctl raw 0801C00000011101

Common Daemon Commands

These can be typed into the UI command bar (c key) or sent via exn_gsdctl:

• CONNECT: Open the link to the device.
• DISCONNECT: Close the link.
• PING: Send a test PUS packet.
• HK_REQ: Request housekeeping data.