IMU PLACEMENT STUDY

LoRa Autonomous Boat Controller

An embedded-systems project spanning STM32 firmware, LoRa communication, PCB reconstruction and a documented V2 redesign. The original university boat controller is preserved as V1; the next vehicle node and a voice/text/location handheld are under development.

Current milestone: engineering review edition. The schematics, source code, parts and build procedures are available for inspection. V2 is not fabrication-ready, and the preserved V1 firmware build is not hardware-qualified.

Portfolio case study · Application handbook · Build and assembly guide · Latest verification · Project history

Existing controller	Developing controller
V1: 44 physical components, reconstructed from original fabrication evidence	V2: 118 physical references, 80 × 46 mm board draft

These are CAD renders. They do not establish that the V2 board has been manufactured or tested.

Explore the project

Clone or download the repository, then open pm/index.html locally. For the complete interactive workspace with searchable BOMs, datasheets, drawings, connector evidence and assembly/programming guides:

node pm/tools/serve.mjs

Open http://127.0.0.1:8765/pm/. The viewer runs locally and requires no account or package installation. GitHub displays the HTML source; it does not run the viewer from a repository file link. See viewer instructions.

The portfolio handoff and structured project data provide captions, asset paths, result evidence and claim boundaries for a portfolio site.

Architecture and implementation

flowchart LR
  Handset[External handset] <-->|LoRa radio link| Radio[Reyax UART radio]
  Radio <-->|UART| MCU[STM32F446 vehicle controller]
  GPS[GNSS receiver] -->|NMEA UART| MCU
  MCU -->|PWM| ESC[Propulsion ESC]
  MCU -->|PWM| Servo[Steering servo]
  Battery[Battery and regulation] --> MCU

V1 firmware is bare-metal C using STM32 HAL/CMSIS, with UART radio commands, GPS parsing and two PWM outputs. The original handset source is not included. The current code has known failsafe, parsing and pin-role issues documented in the firmware audit.

Hardware originated in Cadence OrCAD/Allegro and has been reconstructed in KiCad 9. Python tools generate and inspect schematics, compare complete pin groups and prepare assembly evidence. The viewer uses HTML, CSS and JavaScript with embedded project data; Node.js builds and validates it. GitHub Actions separates portable repository checks from optional native CAD and firmware jobs.

V2 adds draft provisions for protected power, a separate actuator rail, sensing and USB/debug access. The separate Stage A diagnostic now builds for board identity and inactive actuator outputs. Corrected control firmware, autonomous navigation and the proposed voice/text/location handheld remain development targets. Voice airtime and RC coexistence must be validated before choosing handheld hardware.

What has been demonstrated

The integrated V2 ground repair reduces three unconnected PCB items to zero, with zero ordinary DRC errors and unchanged warning/parity counts. The fresh native review preserves all 533 electrical pins. One V2 ERC warning remains; the strict review also flags the intentional PCB change against its older preservation baseline. Six component-limit blockers require circuit corrections before fabrication. No range, voice or autonomous-navigation performance is claimed by these software/CAD results.

Build, review and contribute

• V1 assembly and inspection · V1 backup/flashing procedure
• V2 assembly review · V2 firmware bring-up plan
• Safe schematic-only regeneration · Reproducible firmware build
• Independent review workflow · Publication and portability record

Do not run full PCB generation or routing merely to refresh drawings. The schematic-only command preserves the existing PCB, project and BOM. Native KiCad checks require KiCad 9; the V1 build requires the recorded GNU Arm toolchain. No CI job flashes real hardware.

The IMU interface candidate now implements the proposed 1.8 V supply and I2C/interrupt translation in a separately checked schematic. It is available in the V2 viewer; live PCB integration is the next layout task.

Next milestones

1. Correct the IMU's 1.8 V interface and the five remaining power/signal-limit findings; reconcile schematic-to-PCB differences.
2. Build on the separate Stage A diagnostic: freeze the operational protocol, implement supervised outputs and measure failsafe behavior.
3. Complete part/footprint qualification, the V2 connector atlas and staged physical bring-up.
4. Validate voice quality, radio airtime and RC scheduling before developing the handheld.

Provenance and attribution

The original controller was a University of Arkansas EECS senior-design team project; the repository identifies May 2025 fabrication evidence. The current reconstruction, documentation and review tooling include AI-agent-assisted development. Individual original team contributions should be confirmed before using first-person portfolio claims.

Allegro/ preserves original source evidence. Read provenance and conversion limits before interpreting the reconstructed geometry or inferred drill data. Third-party firmware and tools retain their existing notices; no new project-wide license is granted by this documentation.