Rust-Embedded Weather Station
Author: Tusca Mircea
GitHub Project Link: Weather Station
1. Functional Description
The Rust-Embedded Weather Station is a compact, battery-powered device built on the RP2040 microcontroller that continuously monitors key environmental parameters. It reads:
- Temperature & Humidity via a DHT22 sensor
- Atmospheric Pressure via a BMP280 sensor
- Ambient Light Level via a BH1750 sensor
- Air Quality (volatile compounds proxy) via an MQ-135 gas sensor
All sensor data are acquired asynchronously using the Embassy framework, processed on-board, and displayed in real time on a 0.96″ SSD1306 OLED screen.
2. Motivation
The motivation for this project was the desire to create a device that would be useful in daily life and that will operate with a lot of data, giving the posibility of exploring how different sensors work with each other and how the data could be managed and used inside the software.
3. System Architecture
The overall system is organized into three main subsystems—Sensing, Processing, and Output—all coordinated by the RP2040 microcontroller running Rust/Embassy firmware.
Subsystems
-
Sensing Subsystem
- DHT22 (temperature & humidity): single-wire digital interface
- BMP280 (pressure): I²C bus
- BH1750 (light): I²C bus
- MQ-135 (air quality): analog voltage via ADC
-
Processing Subsystem (RP2040 + Embassy)
- Async executor
- Sensor-reader tasks (one per sensor), each sampling on its own schedule
- Inter-task channels (
embassy_sync::channel) to serialize and buffer readings - Data formatting (convert raw counts/voltages into human-readable units)
The HC-06 is a serial-port-profile (SPP) Bluetooth 2.0 module that acts as a wireless UART slave. It’s ideal for streaming sensor data to a phone or PC:
- Supply voltage: 3.3 V–6 V (power from the USB 5 V rail is fine)
- Logic level: 3.3 V on TX/RX
- Default baud rate: 9600 bps (configurable via AT commands)
- Pins:
- VCC → 5 V (USB)
- GND → GND
- TX → RP2040 RX
- RX → RP2040 TX
microSD SPI Module
This breakout makes adding removable flash storage trivial via the RP2040’s SPI peripheral:
-
Interface: SPI (CS, SCK, MOSI, MISO)
-
Supply & level shifting:
- VCC accepts 5 V (on-board regulator → 3.3 V)
- Logic-level shifters on data lines
-
Supported cards: microSD / SDHC up to 32 GB (Class 10 recommended)
-
Pins:
- GND → GND
- VCC → 5 V (USB)
- CS → any free GPIO
- SCK → SPI0_SCK
- MOSI → SPI0_MOSI
- MISO → SPI0_MISO
-
Output Subsystem
- SSD1306 OLED: I²C display task subscribes to the channel of aggregated reading
Data Flow
-
Sensor sampling
- Each sensor-task wakes on a timer, performs its read (I²C transaction or ADC conversion), then packages a measurement struct.
-
Channel exchange
- Measurement structs are sent into a bounded Embassy channel, decoupling sampling rate from display refresh.
-
Aggregation & formatting
- A dedicated “display” task collects the latest value from each sensor channel, formats strings (“T=23.5 °C”, “RH=45 %”, etc.).
-
Display update
- The display task issues I²C write sequences to the SSD1306, refreshing the on-screen dashboard at a fixed interval (e.g. 1 Hz).
4 Hardware Components
- RP2040-Zero: Dual-core ARM Cortex-M0+ microcontroller running the Rust/Embassy firmware; orchestrates sensor reads, data processing, and I/O.
- DHT22 (AM2302): Single-wire digital sensor for temperature (±0.5 °C) and humidity (±2 % RH), updates every ≥2 s.
- BMP280: I²C barometric pressure and temperature sensor; provides high-resolution pressure (Pa) and temperature (°C) readings.
- BH1750: I²C ambient light sensor; measures illuminance in lux for display and adaptive logic.
- MQ-135: Analog gas sensor; outputs voltage via ADC proportional to air-quality (volatile compounds proxy).
- SSD1306 OLED (0.96″): I²C monochrome display; renders real-time text/graphics of sensor values at ~1 Hz.
- microSD SPI Module: SPI flash storage breakout; logs timestamped CSV sensor data to a microSD card.
- HC-06 Bluetooth Module: UART SPP slave device; streams ASCII-formatted sensor readings over Bluetooth at a default 9600 bps.
Bill of Materials
| Device | Usage | Price |
|---|---|---|
| RP2040-Zero development board | Main MCU | 7.88 € |
| DHT22 AM2302 sensor | Temperature & humidity measurement | 8.54 € |
| BMP280 pressure/temperature sensor | Barometric pressure & temperature | 2.01 € |
| BH1750 GY-302 light sensor | Ambient illuminance measurement | 10.40 € |
| MQ-135 air-quality sensor | Analog proxy for air pollution | 2.73 € |
| 0.96″ SSD1306 OLED display | I²C visual interface for readings | 4.10 € |
| MicroSD SPI Data Logger module | Logs CSV data to microSD via SPI | 4.08 € |
| Patriot microSDHC 16 GB, Class 10 | Storage medium for logged data | 18.80 Lei |
| HC-06 Bluetooth module | Streams data over UART → Bluetooth | 6.88 € |
Software
| Crate / Library | Description | Usage in Project |
|---|---|---|
| embassy | Asynchronous embedded framework | Core async executor and timer scheduling |
| embassy-rp | RP2040 Hardware Abstraction Layer (HAL) | GPIO, I²C, SPI, ADC drivers for the RP2040 |
| embedded-hal | HAL traits | Unified hardware driver interfaces |
| dht-sensor | DHT22 driver | Reads temperature & humidity from the DHT22 |
| bmp280-ehal | BMP280 driver | Interfaces with the BMP280 over I²C |
| bh1750 | BH1750 driver | Interfaces with the BH1750 light sensor |
| ssd1306 | SSD1306 OLED driver | Controls text/graphics on the 0.96″ I²C OLED |
| embedded-graphics | 2D graphics library | Renders fonts and simple graphics on the OLED |
| embedded-sdmmc | FAT filesystem support for SD cards | Manages file I/O (CSV logs) on the microSD card |
| heapless | No-std data structures | Buffers sensor data and display frames without allocator |