Telemetry & Communications

Dual LoRa Radio Modules (RFM95W)

The system utilizes two independent LoRa modules to provide long-range, low-power telemetry links at 915 MHz.

Schematic Snippet: Dual Radio Modules Figure 17: Redundant TRS Radio Modules 0 and 1.

  • Model: HopeRF RFM95W.
  • Interface: Connected via high-speed SPI with dedicated Chip Selects (RADIO_nCS, RADIO1_nCS).
  • Indicators: Visual status is provided by D11 and D39 LEDs, which trigger during active packet transmission.
  • Antenna: Standard 50Ω SMA connectors (J20, J22) are utilized for external dipole or whip antennas.
  • Design Defense: Dual modules allow for frequency hopping or redundant data streams, ensuring telemetry persists even if one antenna path is compromised.

GNSS Navigation (u-blox ZOE-M8Q)

For absolute positioning and time-synchronization, the ECU features a high-sensitivity u-blox GNSS module.

Schematic Snippet: GPS/GNSS Module Figure 18: ZOE-M8Q implementation with RF shielding and active filtering.

  • Model: u-blox ZOE-M8Q.
  • EMI Protection: The module is housed within a dedicated RF Shield to prevent internal ECU logic noise from desensitizing the GPS receiver.
  • Interface: Connected via UART (GPS_RXD/TXD) for standard NMEA sentence parsing.
  • Antenna: Fed through a 50Ω microstrip to an SMA connector (J15) for external active/passive GPS antennas.

Ground-Test Ethernet (Grid Connect XPort)

A hardwired Ethernet interface is provided for high-bandwidth data offloading and ground station commanding during pad operations.

Schematic Snippet: Ethernet Interface Figure 19: GC-XPORT-ENH Serial-to-Ethernet implementation.

  • Model: Grid Connect GC-XPORT-ENH.
  • Protocol: Functions as a Serial-to-Ethernet bridge, allowing the STM32 to communicate over TCP/UDP via its internal USART interface.
  • Stability: Utilizes a 10uF decoupling capacitor (C6) to stabilize the 3.3V rail during high-speed data bursts.
  • Control: The ETH_nRST line allows the MCU to power-cycle the module if a network hang is detected.

Communication Fail-Safes

  • Independent Resets: Both LoRa radios and the Ethernet module have discrete reset lines tied to the MCU, preventing single peripheral hang from locking the communication bus.
  • EMI Zoning: All RF connectors (SMA) are positioned at the board edge, away from the 24V propulsion regulation zone, to maximize signal-to-noise ratio (SNR).