Flight computer

PERRII – Aerospace Flight Computer version 2

Project Overview

PERRII is a modular aerospace flight computer designed for environmental sensing and long-range data telemetry. The system is built around the ESP32-S3 Zero microcontroller and is designed to function as a scientific payload for high-altitude ballooning or atmospheric research. It integrates precision GNSS positioning, environmental gas sensing (Methane and Ammonia), and a robust power regulation system.

My Contribution: LoRa Communication Subsystem

As the lead for the communication system, I was responsible for the hardware integration and signal integrity of the long-range telemetry link.

Key Technical Implementations:

• RFM98W Integration: Integrated the RFM98W-433S2 LoRa transceiver to provide a robust, low-power, long-distance communication link between the flight computer and the ground station.
• RF Hardware Design: Designed the antenna interface for the AE1 Antenna, including a 100pF decoupling capacitor (C5) to ensure signal stability.
• SPI Interface Management: Configured the SPI bus (MOSI, MISO, SCK, NSS) to interface the RF module with the ESP32-S3, managing critical interrupt lines (DIO0-DIO5) for real-time packet handling.
• RF Layout Optimization: Optimized the trace routing between the RF transceiver and the antenna connector to maintain signal integrity in a compact, circular PCB form factor.

System Architecture

While my primary focus was the communication link, I worked closely with the team to integrate the following subsystems:

1. Navigation & Sensing

• GNSS Positioning: Integration of a u-blox CAM-M8C-D GPS module for real-time tracking.
• Environmental Monitoring: Active monitoring of atmospheric data via SEN1 (Methane) and SEN2 (Ammonia) gas sensors.
• Visual Telemetry: A dedicated LED altitude output array driven by the AW9523B LED driver.

2. Power Management

• Dual-Stage Regulation: The system utilizes a high-efficiency LM2596S-5 switching buck converter for the primary 5V rail and an LM1117DT-3.3 LDO for the sensitive logic and RF rails.
• Robust Input: Featuring XT-30 battery connectors and reverse polarity protection via a D10 Schottky diode.

Design Files

1. Schematic Design

The schematic follows a modular design separated into Power, TX, Sensor, and GPS blocks.

2. PCB Layout

A circular 2-layer board designed for cylindrical aerospace housing.

Team & Credits

• Lok Yu Lui (Rain): Hardware Engineer – LoRa Communication Subsystem, Power Systems, and Sensor Payloads.
• PERRII Team: Collaborative effort for MCU integration and software.