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
Refine this doc
Ask about this doc
Firmware Getting Started
Target: ESP-IDF on Heltec WiFi Kit 32 V3 (ESP32-S3). The exact Heltec board is represented by two 1x18 receptacle interfaces because the exact board part was unavailable.
GPIO / header mapping
Table
| Function | Heltec header interface | ESP32-S3 GPIO from PDF header map | Net |
|---|---|---|---|
| GPS UART RX (receives GPS TX) | JH1 pin 5 | GPIO44 / U0RXD | GPS_RX_ESP |
| GPS UART TX (drives GPS RX) | JH1 pin 6 | GPIO43 / U0TXD | GPS_TX_ESP |
| I2C SDA | JH1 pin 12 | GPIO7 | I2C_SDA |
| I2C SCL | JH1 pin 13 | GPIO6 | I2C_SCL |
| MPU6050 interrupt | JH1 pin 14 | GPIO5 | IMU_INT |
| Buzzer output | JH1 pin 15 | GPIO4 | BUZZER_GPIO |
| TWAI RX | JH1 pin 16 | GPIO3 | CAN_RX |
| TWAI TX | JH1 pin 17 | GPIO2 | CAN_TX |
| Payload/module enable | JH1 pin 18 | GPIO1 | BUS_EN |
External module headers
- J7 MPU6050: 1=3V3, 2=GND, 3=SDA, 4=SCL; J13 pin 1=IMU_INT.
- J2 BMP280: 1=3V3, 2=GND, 3=SDA, 4=SCL.
- J3 GY-271: 1=3V3, 2=GND, 3=SDA, 4=SCL.
- J4 GPS: 1=3V3, 2=GPS_RX input (MCU TX), 3=GPS_TX output (MCU RX), 4=GND.
- J5 SN65HVD230 logic/power: 1=3V3, 2=GND, 3=CTX/CAN_TX, 4=CRX/CAN_RX.
- J6 SN65HVD230 bus/aux: 1=CANH, 2=CANL, 3=GND, 4=BUS_EN if supported; otherwise leave module-side pin unconnected.
ESP-IDF initialization sketch
C
// GPIO numbers above are board-header mappings from the reference PDF. i2c_master_bus_config_t i2c_cfg = { .sda_io_num = 7, .scl_io_num = 6, .clk_source = I2C_CLK_SRC_DEFAULT }; twai_general_config_t can_g = TWAI_GENERAL_CONFIG_DEFAULT(2, 3, TWAI_MODE_NORMAL); // UART0 pins 43/44 may conflict with programming/logging; use a remapped UART controller if USB-CDC is preferred.
Startup sequence
- Set GPIO4 low and GPIO1 to the safe mission default.
- Initialize I2C at 100 or 400 kHz; probe sensor module addresses.
- Configure GPIO5 as interrupt input per MPU6050 module polarity.
- Initialize GPS UART with RX=44, TX=43 (commonly 9600 baud for NEO-6M modules).
- Initialize TWAI with TX=2, RX=3 and the mission bus bitrate; termination is external.
- Start sensor, navigation, telemetry, and buzzer tasks.
Do not enable extra board-level I2C pull-ups unless the external breakout pull-ups are removed/disabled; the OBC contains one 4.7 kΩ pair.
GPIO / header mapping
External module headers
ESP-IDF initialization sketch
Startup sequence
