Update README.md

README.md

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 # ModTOS
 
-Modbus RTU driver for STM32 + FreeRTOS with interrupt‑driven frame handling and RS485 GPIO direction control.
+Modbus RTU driver for STM32 + FreeRTOS with interrupt-driven frame handling and RS485 GPIO direction control.
+
+## Overview
+
+ModTOS is a lightweight, dependency-free Modbus RTU slave implementation intended for use in embedded systems based on STM32 and FreeRTOS. It is designed to operate as a cooperative background task, minimizing CPU usage and avoiding interference with time-sensitive application logic.
+
+The driver uses interrupt-based UART reception with idle line detection to capture complete RTU frames without polling. RS485 transceiver direction is controlled via a user-defined GPIO pin, allowing the driver to support half-duplex serial communication in industrial settings.
+
+## Features
+
+- Function Code 0x03 Read Holding Registers
+- Function Code 0x10 Write Multiple Holding Registers
+- CRC-16 validation and exception handling
+- Flat register buffer 128 x `uint16_t`
+- Task-based integration with optional stats tracking
+- No dynamic memory allocation
+- Easily adaptable to polling or non-RTOS environments
+
+## Integration Notes
+
+- Requires UART configured with idle line detection
+- GPIO pin needed for RS485 DE/NRE control
+- Designed for projects where Modbus functionality must coexist with high-speed control tasks