Rocket OBC Design
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Created 4 project docs
Project Specification
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
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.
The FFC 3.3 V pins are auxiliary low-current distribution only. This budget do...
Firmware Getting Started
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.
- Configure safe GPIO defaults; keep buzzer off.
- Initialize I2C and probe expected addresses.
- Configure IMU interrupt input.
- Initialize GPS UART.
- Initialize TWAI at the mission bus bit rate; termination is external.
- Start sensor acquisition and telemetry tasks.
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
- Import/create the exact
10051922-1210ELFconnector. - Review the schematic and documented FFC pinout.
- Place components on the circular PCB.
- 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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Power Budget
Scope
3.3 V OBC rail only. Excludes the 24 external payload boards and any high-current load beyond the FFC boundary.
Table
| Load | Typical assumption | Peak assumption |
|---|---|---|
| Heltec WiFi Kit 32 V3 / ESP32-S3 radio | 150–250 mA | 500 mA transient |
| MPU6050 module | 4 mA | 10 mA |
| BMP280 module | 1 mA | 3 mA |
| GY-271 magnetometer module | 5 mA | 15 mA |
| GY-NEO6MV2 GPS module | 45 mA | 70 mA |
| SN65HVD230 module | 15 mA | 50 mA during bus activity |
| Buzzer stage | 0 mA off | 30–80 mA (part-dependent) |
| Margin / indicators / leakage | 25 mA | 75 mA |
| Estimated total | 245–345 mA | ~800 mA conservative peak |
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 does not authorize powering all 24 payload nodes through the OBC/FFC harness.
Scope
Input and Protection Sizing
FFC Power Limitation
