Rocket OBC Design

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Block Diagram

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Project document created

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
J_PWR
BZ1
C7
Capacitance
10uF
R3
Resistance
1kΩ
C5
Capacitance
100nF
R1
Resistance
4.7kΩ
C2
Capacitance
100nF
C1
Capacitance
100nF
C6
Capacitance
100nF
R2
Resistance
4.7kΩ
C4
Capacitance
100nF
R4
Resistance
100kΩ
C3
Capacitance
100nF
J2
J5
J1
J7
Q1
JH1
J13
J6
J4
J3
FPC1
FPC4
FPC3
F1
FPC2
FPC5

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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.

Rocket Payload OBC

Rocket Payload OBC thumbnail
3.3 V ESP32-S3 rocket payload OBC with I2C sensors, GPS UART, CAN payload interface, and buzzer control.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$4.60–$4.96

Digi-Key

$1.57

HQonline

$0.12

LCSC

$7.63–$7.69

Mouser

$6.49–$6.78

TME

$0.00

Verical

$4.17–$6.99

Controls