Embedded-Rust-Temperature-Checker-RP2040

A robust temperature logging system developed in Rust for the Raspberry Pi Pico (RP2040). The system supports multiple configurations, provides USB CDC data export fpr thermal printing (which can be configured to a .txt format), and includes comprehensive analytics for detailed monitoring and evaluation.

Features

• 🌡️ DHT22 Temperature & Humidity Sensing
• 🖨️ Text Output with formatted receipts
• ⏰ Multiple RTC Options (Built-in, DS3231, Software-based)
• 🔢 Print Counter with automatic summaries
• 💻 USB Serial Interface for commands and monitoring
• 📝 File Logging Support (SD card ready)
• 🔄 Configurable Reading Intervals

Hardware Requirements

Basic Setup

• Raspberry Pi Pico (RP2040-based board)
• DHT22 temperature/humidity sensor
• Micro USB cable for power and communication

Optional Hardware

• DS3231 RTC Module (for persistent timekeeping)
• SD Card Module (for file logging)
• Breadboard and jumper wires

Wiring Diagram

RP2040 Pico          DHT22 Sensor
├─ GPIO 2     ────── Data Pin
├─ 3.3V       ────── VCC
└─ GND        ────── GND

Optional DS3231 RTC:
├─ GPIO 4 (SDA) ──── SDA
├─ GPIO 5 (SCL) ──── SCL
├─ 3.3V         ──── VCC
└─ GND          ──── GND

USB Serial:
└─ USB Port     ──── Connect to computer/hub

Software Setup

Prerequisites

1. Rust (latest stable version)
2. cargo-embed or probe-rs for flashing
3. Serial terminal (like PuTTY, screen, or minicom)

Installation

1. Clone the repository:

git clone https://github.com/yourusername/rp2040-temp-logger.git
cd rp2040-temp-logger

2. Install Rust embedded tools:

rustup target add thumbv6m-none-eabi
cargo install cargo-embed

3. Configure your hardware in main.rs:

   • Choose your RTC implementation (lines 400-430)
   • Set initial date/time
   • Configure pin assignments if different

4. Build and flash:

cargo embed --release

RTC Implementation Options

Option 1: Built-in RP2040 RTC (Default)

// Already configured in main.rs
let mut rtc = BuiltInRTC::new(pac.RTC, &mut pac.RESETS);

• ✅ No extra hardware needed
• ✅ Simple setup
• ❌ Loses time on power loss

Option 2: DS3231 External RTC (Recommended)

// Uncomment DS3231 section in main.rs
let mut rtc = DS3231RTC::new(i2c);
rtc.set_datetime(2024, 8, 23, 14, 30, 0).ok();

• ✅ Battery backup
• ✅ High precision (±2ppm)
• ✅ Built-in temperature sensor
• ❌ Requires additional hardware

Option 3: Software RTC

// Uncomment Software RTC section in main.rs
let rtc = SoftwareRTC::new(start_unix_timestamp, start_ticks, 1_000_000);

• ✅ No hardware needed
• ✅ Network time sync capable
• ❌ Resets on power cycle

Usage

Serial Commands

Connect to the device via USB serial (115200 baud) and use these commands:

Command	Description
start	Begin temperature logging
stop	Stop logging and show summary
status	Show current status and last reading time
summary	Display detailed analytics
recent	Show last 10 readings with differences
help	Show all available commands

Thermal Printer Output

Each reading produces a formatted receipt:

================================
    TEMPERATURE READING
================================
Reading #1
Time: 2024-08-23 14:30:00
Temperature: 22.5°C
Humidity: 45.0%
--------------------------------
Powered by RP2040 + Rust
RTC Status: OK
================================

Configuration

Reading Intervals

Modify in main.rs:

const READING_INTERVAL: u32 = 300_000_000; // 5 minutes in microseconds

Print Counter Summary Frequency

const SUMMARY_INTERVAL: u32 = 10; // Every 10 readings

Log Buffer Size

log_entries: Vec<TempLogEntry, 50>, // Store last 50 readings

Project Structure

src/
├── main.rs                 # Main application logic
├── lib.rs                  # Library definitions
└── components/
    ├── dht22.rs           # DHT22 sensor driver
    ├── rtc/
    │   ├── builtin.rs     # Built-in RTC implementation
    │   ├── ds3231.rs      # DS3231 external RTC
    │   └── software.rs    # Software RTC
    ├── thermal_printer.rs  # Thermal printer interface
    ├── logger.rs          # Temperature logging system
    └── serial.rs          # USB serial interface

Cargo.toml                 # Dependencies and configuration
memory.x                   # Memory layout
.cargo/                    # Cargo configuration
├── config.toml
└── embed.toml

Dependencies

Key Rust crates used:

[dependencies]
rp-pico = "0.8"                    # RP2040 HAL
cortex-m = "0.7"                   # ARM Cortex-M
embedded-hal = "0.2.5"             # Hardware abstraction
embedded-time = "0.12"             # Time handling
dht-sensor = "0.2"                 # DHT22 support
usb-device = "0.2"                 # USB functionality
usbd-serial = "0.1"                # USB serial
heapless = "0.7"                   # No-std collections
nb = "1.0"                         # Non-blocking APIs
panic-halt = "0.2"                 # Panic handler

Troubleshooting

Common Issues

DHT22 not responding:

• Check wiring connections
• Ensure 3.3V power supply
• Try different GPIO pin
• Add pull-up resistor (4.7kΩ) on data line

RTC time incorrect:

• For built-in RTC: Set time after each power cycle
• For DS3231: Check battery and I2C connections
• Verify I2C address (0x68 for DS3231)

Serial commands not recognized:

• Ensure 115200 baud rate
• Use line endings (CR/LF)
• Check USB drivers
• Try different terminal software

Debug Output

Enable debug logging by modifying the panic handler:

use panic_semihosting as _; // Instead of panic_halt

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Code Style

• Use cargo fmt for formatting
• Run cargo clippy for linting
• Follow embedded Rust best practices
• Document public APIs

Future Enhancements

• Web Interface via WiFi module
• Data Visualization with graphs
• Alert System for temperature thresholds
• Multiple Sensor Support
• Network Time Sync (NTP)
• MQTT Integration
• Battery Power Management
• Enclosure Design (3D printable)

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Raspberry Pi Foundation for the RP2040 microcontroller
• Rust Embedded Working Group for excellent embedded support
• DHT22/AM2302 sensor manufacturers

Support

For questions, issues, or contributions:

• 📧 Email: your-email@example.com
• 🐛 Issues: GitHub Issues
• 💬 Discussions: GitHub Discussions

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