Ground Segment (GS) Subsystem
The Ground Segment (GS) is the terrestrial component of the FlatSat Learning Kit, acting as the bridge between the satellite and the operator. Its primary role is to mimic a real-world satellite ground station by receiving telemetry from the FlatSat and transmitting telecommands to control its mission.
System Overview
The Ground Segment is built on a high-performance architecture designed for reliable long-range communication and seamless computer integration.
1. Processing and Control
- Microcontroller: It is powered by the STM32F103RC MCU, which handles the complex tasks of modulating/demodulating radio signals and managing the serial interface with the user's computer.
- Computer Interface: A USB-C connection provides both power to the module and a high-speed data link (via ST-Link) for the operator to send commands and view real-time satellite data.
2. Wireless Communication
- Radio Module: Equipped with an RFM98PW radio module, the Ground Segment communicates on the 433 MHz frequency band.
- Performance: It is capable of a high transmit power of 27 dBm, ensuring a strong link even in challenging environments.
- Data Handling: The system supports a data rate of 9.6 kbps, optimized for reliable transmission of satellite telemetry packets.
3. Hardware Connectivity
- SPI Interface: The MCU communicates with the radio module using a dedicated high-speed SPI bus (MOSI: PA7, MISO: PA6, SCK: PA5, NSS: PB6).
- Digital I/O: Multiple digital pins (PA8–PA10, PC1, PC7, PC8) are utilized for radio interrupts and reset signals to ensure robust operation.
- Clock Accuracy: The board includes a 16MHz High-Speed External (HSE) crystal and a 32.768kHz Low-Speed External (LSE) crystal for precise timing during data processing.
Technical Specifications
| Feature | Specification |
|---|---|
| Processor | STM32F103RC (ARM Cortex-M4) |
| Radio Frequency | 433 MHz |
| Transmit Power | 27 dBm |
| Data Rate | 9.6 kbps |
| PC Connection | USB-C (UART via ST-Link) |
| Antenna | Integrated and External connector support |
Example Code
The following code provides a complete setup for the Ground Segment, enabling it to transmit and receive radio packets. This script is essential for establishing the first "handshake" between your ground station and the FlatSat.
| Feature | Description | Code Link |
|---|---|---|
| GS TX/RX | Initialize the Ground Segment radio and perform basic transmit/receive operations. | gs_tx_rx.ino |
User Note: When deploying your Ground Segment, ensure the radio settings (Frequency, SyncWord, and Bitrate) exactly match those configured on the satellite's Communication module to establish a successful link.