STM32 FreeRTOS Multi-Sensor Data Logger

This repository contains the full source code and documentation for a real-time, multi-sensor environmental data logger built on an STM32F767ZI Nucleo board using the FreeRTOS operating system.

The system concurrently reads data from a DHT11 (temperature/humidity) and a capacitive soil moisture sensor, processes the data for accuracy, and displays it on a graphical OLED screen. This project is a comprehensive example of a real-world embedded system, covering hardware interfacing, custom driver development, RTOS architecture, and a polished user interface.

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🔑 Key Features

• Real-Time & Multitasking
  Built on FreeRTOS with a pre-emptive scheduler, featuring two concurrent tasks for sensing and display that communicate safely using a message queue and mutex.

• Robust Sensor Drivers
  Includes a custom, RTOS-aware driver for the DHT11 with a pre-scheduler "cranking" routine to handle hardware instability and a context-aware critical section to protect timing from RTOS interrupts.

• Advanced Data Filtering
  Uses ADC oversampling to reduce noise from the analog soil sensor and applies a linear mapping function with user-calibrated values for accurate percentage readings.

• Graphical User Interface (GUI)
  A clean, professional UI on an SH1106 OLED display using the U8g2 library, featuring a startup splash screen and graphical progress bars.

• System Status Indicators
  Utilizes the onboard LEDs to provide at-a-glance feedback: a blinking/solid blue LED for the DHT11's startup status and a green LED that serves as a "soil is dry" warning.

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🔧 Hardware Components

Component	Model
Microcontroller	STM32F767ZI Nucleo-144
Temperature Sensor	DHT11 Sensor Module
Soil Moisture	Capacitive Soil Moisture Sensor v1.2
Display	1.3" SH1106 I2C OLED

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💻 Software & Tools

• IDE: STM32CubeIDE
• OS: FreeRTOS (CMSIS-RTOS v2 API)
• Libraries: STM32 HAL, U8g2 Graphics Library

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⚙️ How It Works

The system architecture is designed around two main tasks:

• sensorTask
  This task runs periodically every two seconds. It reads the raw sensor values, applies oversampling and calibration logic, and then sends the final, processed data to a message queue.

• displayTask
  This task is event-driven. It waits for data to arrive in the message queue, and upon receiving it, it takes control of the I2C bus via a mutex to update the OLED display with the new information.

This decoupled design ensures that the sensor reading and display updates operate independently, creating a responsive and stable system.

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📁 System Configuration

For detailed hardware pin mapping, FreeRTOS task design, CubeMX peripheral settings, and software module breakdown, refer to:

👉 👉 System_Setup_Guide.md

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To integrate the U8g2 OLED graphics library (used for SH1106 OLED display), follow the detailed instructions provided in:

👉 U8g2 OLED Driver Setup Guide

This guide explains how to:

• Copy required .h and .c files to the correct project folders.
• Configure include paths and GCC linker settings in STM32CubeIDE.
• Successfully compile and use the U8g2 library with FreeRTOS and STM32.

Working_Videos_and_Images

This folder contains visual demos showcasing the real-time working of the RTOS-Based Multi-Sensor Data Logger project.

🎬 Demo Videos

👉 Watch working demo videos in the Working_Videos_and_Images folder:

1. - OLED Display Output

• Shows the live sensor values (temperature, humidity, soil moisture) rendered using the u8g2 graphics library on a 1.3” SH1106 OLED screen.

2. - Terminal + Hardware View

• Shows UART output on serial terminal and physical hardware in operation, including LED feedback during DHT11 initialization and task scheduling under FreeRTOS.

These videos provide both internal (software) and external (hardware) views of the system.

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