A comprehensive bare-metal 2D scanning system and multi-sensor security alarm built with Rust and Embassy on the STM32.
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Author: DULCE Andrei-Marian
GitHub Project Link: https://classroom.github.com/a/sVB0pKHF
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This project is an advanced, multi-layered active security and environmental monitoring hub built on the STM32. The core feature is a 2D scanning system using a VL53L0X Time-of-Flight (ToF) sensor mounted on a 28BYJ-48 stepper motor, which streams Cartesian coordinate data to a laptop via USB Bulk transfers to render a real-time radar map. Additional sensors provide intrusion detection and environmental telemetry.
I chose this project because it combines precise motor control, real-time data acquisition from a vast array of sensors, and PC-device USB communication into a single robust system. It is a highly practical and technically challenging way to explore asynchronous embedded programming in Rust.
Main software and system components:
- Scanning Module: reads distance from VL53L0X via I2C and steps motor via GPIO.
- Intrusion Detection Module: reads Doppler radar, vibration, and sound sensors.
- Access Control Module: handles the 4x4 matrix keypad and IR receiver.
- Environmental Module: reads BMP180 (I2C) and photoresistors (ADC).
- Local Feedback Module: controls the 4-digit display, buzzer (PWM), and LEDs.
- Communication Module: sends serialized coordinate payloads via USB Bulk to the PC.
- Established the project idea and worked on the component list.
- Ordered all hardware components (STM32, VL53L0X, stepper motor, etc.).
- Researched the Embassy framework and USB Bulk transfer implementation in Rust.
- Components arrived, started testing and tinkering with them.
- Hardware Integration. Began assembling the core scanning module by mounting the VL53L0X ToF sensor to the 28BYJ-48 stepper motor shaft.
- Circuit Prototyping. Mapped out the pin connections on the 830-point breadboard for the I2C bus (sensor), GPIO sequence (ULN2003 driver), and the security sensor array.
- Software Design. Drafted the Embassy task architecture, defining the synchronization channels between the scanning task and the USB communication task.
The system uses an STM32 Nucleo-U545RE-Q as the central hub. It orchestrates a VL53L0X ToF sensor mounted on a 5V stepper motor for spatial scanning, alongside a suite of security sensors (Doppler radar, vibration, sound, keypad) and environmental sensors (BMP180, photoresistors). Everything is wired on a universal 830-point breadboard.
To be added.
| Device | Usage | Price |
|---|---|---|
| STM32 Nucleo-U545RE-Q | The main microcontroller | 106.59 RON |
| VL53L0X ToF Sensor | Distance measurement (I2C) | 28.00 RON |
| Universal Breadboard 830 points | Prototyping base | 15.67 RON |
| 28BYJ-48 5V Stepper Motor + ULN2003 Driver | Motor for sensor sweeping | 15.00 RON |
| RCWL-0516 Doppler Radar Sensor | Microwave motion detection | 5.00 RON |
| BMP180 Sensor Module | Temperature and pressure sensing (I2C) | 10.00 RON |
| 4x4 Matrix Keypad | PIN code input for security | 8.00 RON |
| 0.56" 4-Digit 7-Segment Display | Local numerical data display | 10.00 RON |
| Passive Buzzer 3.3V | Proximity audio alarm (PWM) | 3.00 RON |
| 4x Photoresistors | Ambient light sensing (ADC) | 4.00 RON |
| Vibration / Tilt Sensor | Tamper detection | 3.00 RON |
| Microphone / Sound Sensor | Acoustic trigger | 5.00 RON |
| KY-022 IR Receiver & KY-005 Transmitter | Remote control interface | 6.00 RON |
| 10x LED 5mm (Mixed colors) | Directional and status visual indicators | 5.00 RON |
| Transistors (2N2222, BC547) & Diodes (1N4148) | Signal switching and protection | 10.00 RON |
| Assorted Resistors (220Ω, 330Ω, 1kΩ, 4.7kΩ, 10kΩ) | Current limiting and pull-ups/downs | 5.00 RON |
| Capacitors (100uF, 470uF, 100nF) | Power filtering and decoupling | 15.00 RON |
| Dupont Wires (M-M, M-F, F-F) & Jumpers | Establishing connections | 10.00 RON |
| Switches & PCB Buttons | Power control and inputs | 15.00 RON |
| Total | 279.26 RON |
| Library | Description | Usage |
|---|---|---|
| embassy-stm32 | Async HAL for STM32 | Hardware access for I2C, GPIO, ADC, and PWM |
| embassy-executor | Async task executor | Schedules concurrent firmware tasks |
| embassy-time | Embedded timers | Delay management and periodic sensor polling |
| embassy-usb | USB device stack | Implementing USB Bulk endpoints for PC communication |
| embassy-sync | Async synchronization primitives | Providing Channels and Signals to safely move sensor data between tasks. |
| embassy-embedded-hal | Adapter for Embedded HAL | Bridging Embassy drivers with the standard Rust embedded ecosystem. |
| keypad-rs | Matrix keypad driver | Scanning and debouncing the 4x4 input matrix |
| postcard | Compact binary serialization | Serializing coordinate and security data into tiny packets for USB transmission. |
| serde | Data serialization framework | Core framework used by Postcard to define the structure of analytics sent to the PC. |
| cortex-m | ARM Cortex-M low-level access | Handling low-level CPU operations and critical sections. |
| cortex-m-rt | Startup and runtime for ARM | Managing the reset handler and memory initialization of the STM32. |
| panic-probe | Debug panic handler | Catching code crashes and printing the stack trace over the debug probe. |
| defmt | Deferred formatting | Providing high-efficiency logging to debug sensor values in real-time. |
| micromath | no_std math library |
Computing trigonometric functions for coordinate mapping |
| vl53l0x | ToF Sensor Driver | Reading distance data from your laser sensor over I2C. |
| ht16k33 | Segment Display Driver | Controls the 7-segment display. |