Rocket OBC Design

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Block Diagram

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Project Specification

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Project Specification Project Overview
Rocket payload onboard computer (OBC), status: Draft/Review. The board accepts regulated 3.3 V and hosts an ESP32-S3 development module, navigation/environment sensors, GPS, CAN payload networking, and a buzzer driver.
Intended Use
Prototype rocket payload OBC installed on the existing 89.6 mm circular PCB with three existing mounting holes.
What the Device Should Do
  • Operate the Heltec WiFi Kit 32 V3 at 3.3 V logic.
  • Read MPU6050, BMP280, and GY-271-compatible modules over one shared I2C bus.
  • Receive NMEA GPS data over UART and support GPS configuration transmit.
  • Interface the MCU TWAI/CAN controller to an external HiLetgo SN65HVD230 module.
  • Distribute CAN and selected low-current 3.3 V/control signals through payload FFC con...

Power Budget

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Power Budget Scope
3.3 V OBC rail only. Excludes the 24 external payload boards and any high-current load beyond the FFC boundary.
Input and Protection Sizing
  • Upstream regulated 3.3 V source recommendation: at least 1.0 A continuous capability with low transient impedance; 1.5 A preferred margin.
  • Input connector and fuse/protection path: target ≥1 A continuous without excessive voltage drop.
  • Local energy storage: 10 uF bulk plus 100 nF high-frequency bypass at input, with additional local decoupling per external module interface.
  • Because the source is already 3.3 V, series protection must have low resistance; excessive fuse/PTC drop can violate ESP32 brownout margin.
FFC Power Limitation
The FFC 3.3 V pins are auxiliary low-current distribution only. This budget do...

Firmware Getting Started

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Firmware Getting Started
Final GPIO assignments will be populated from the completed schematic. Target framework: ESP-IDF with Heltec WiFi Kit 32 V3 board support.
Required peripherals
  • I2C master: MPU6050, BMP280, GY-271-compatible module interfaces.
  • GPIO interrupt: MPU6050 INT.
  • UART: GPS RX/TX crossed at the connector.
  • TWAI: CAN TX/RX to external SN65HVD230 module.
  • GPIO output: buzzer MOSFET gate.
Startup sequence
  1. Configure safe GPIO defaults; keep buzzer off.
  2. Initialize I2C and probe expected addresses.
  3. Configure IMU interrupt input.
  4. Initialize GPS UART.
  5. Initialize TWAI at the mission bus bit rate; termination is external.
  6. Start sensor acquisition and telemetry tasks.
Electrical notes

flux

Built and verified the complete Rocket Payload OBC schematic. It includes the 3.3 V input protection, WiFi Kit 32 V3 interface, MPU6050/BMP280/GY-271, NEO-6M GPS, SN65HVD230 CAN interface, four active FFC ports plus one DNP port, and MOSFET-driven buzzer. Final ERC review reports no open warnings or errors.
Open items
  • Library uses 10051922-1210EHLF, not the requested 10051922-1210ELF; contact orientation and footprint must be corrected before manufacturing.
  • Modules are represented by verified headers because exact breakout-board parts were unavailable.
  • PCB components are not placed; some footprints remain outside the circular outline.
  • Further execution is paused because no ACUs remain.
Suggested next steps
  1. Import/create the exact 10051922-1210ELF connector.
  2. Review the schematic and documented FFC pinout.
  3. Place components on the circular PCB.
  4. Configure CAN/power trace rules, then route and run DRC.
Fix FFC connector
Review FFC pinout
Place components
Check ERC/DRC
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Files

Schematic

Layout

3D View

Block Diagram
Text
External regulated 3.3 V
  → input connector → fuse/protection → 3V3 rail + 10 uF bulk + 100 nF bypass
  → Heltec WiFi Kit 32 V3 (ESP32-S3)
      ├─ I2C SDA/SCL + one 4.7 kΩ pull-up pair → MPU6050 / BMP280 / GY-271 module headers
      ├─ IMU interrupt ← MPU6050 header
      ├─ UART TX/RX ↔ GY-NEO6MV2 GPS header
      ├─ CAN TX/RX ↔ external SN65HVD230 module header → CANH/CANL → four populated FFC payload connectors + one DNP
      └─ GPIO → gate resistor → NMOS low-side buzzer driver

All blocks share 3V3 and GND. No onboard regulator and no CAN termination. Payload nodes are external beyond the FFC boundary.

## Block sourcing plan
- Power input/protection: from scratch, based on PDF and calculated OBC-only current budget.
- OBC module: exact Heltec WiFi Kit 32 V3 library part if verified; otherwise a verified dual-row module interface matching its header pinout.
- Sensor/GPS/CAN modules: exact verified modules where available; otherwise real labeled connector/header interfaces.
- FFC payload interfaces: exact Amphenol 10051922-1210ELF.
- Buzzer driver: datasheet-backed MOSFET and buzzer/interface.