SRF0X STM32 Library

A lightweight library for interfacing SRF04 and SRF05 ultrasonic distance sensors with STM32 microcontrollers using HAL drivers. Supports blocking measurements in microseconds and centimeters.

Features

• SRF04 & SRF05 Support: Works with both popular ultrasonic modules.
• Microsecond Resolution: Uses a 1 MHz timer for precise pulse-width measurement.
• Simple API: Easy-to-use functions to trigger, read raw pulse width, and get distance in cm.
• Modular Handle: Encapsulate per-sensor configuration in an SRF0X_HandleTypeDef.
• HAL-Based: Leverages STM32Cube HAL; minimal external dependencies.

Table of Contents

• Getting Started

  • Prerequisites
  • Installation

• Usage

  • Initialization
  • Measuring Distance
  • Example

• API Reference

• Contributing

• License

Getting Started

Prerequisites

• Hardware:

  • STM32 microcontroller with Cortex-M core

  • SRF04 or SRF05 ultrasonic sensor

  • Connections:

    • Trig pin → any GPIO output
    • Echo pin → any GPIO input
    • Shared ground and VCC (5 V or 3.3 V as your sensor supports)

• Software:

  • STM32CubeIDE (or any toolchain with HAL libraries)
  • C compiler supporting STM32 HAL

Installation

1. Clone or download this repository:

   git clone https://github.com/alixahedi/SRF0X-STM32.git

2. Copy source files into your project:

   • srf0x.h → your project's Inc/ folder
   • srf0x.c → your project's Src/ folder

3. Include header where needed:

   #include "srf0x.h"

4. Configure peripherals as described below.

Usage

Initialization

1. Configure GPIOs in CubeMX (or code):

   • TrigPin: Output push-pull
   • EchoPin: Input (no pull or pull-down as needed)

2. Configure a timer (e.g., TIM2) for 1 MHz counter:

   • Prescaler = (HAL_RCC_GetPCLK1Freq()/1000000 - 1)
   • Counter mode = up

3. Enable DWT cycle counter (optional, for 10 µs trigger delay):

   CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
   DWT->CTRL    |= DWT_CTRL_CYCCNTENA_Msk;

4. Fill the handle and call srf0x_init():

   SRF0X_HandleTypeDef hsrfx;
   hsrfx.TrigPort = GPIOA;
   hsrfx.TrigPin  = GPIO_PIN_9;
   hsrfx.EchoPort = GPIOA;
   hsrfx.EchoPin  = GPIO_PIN_10;
   hsrfx.htim     = &htim2;  // must be 1 MHz timer
   
   srf0x_init(&hsrfx);

Measuring Distance

• Get raw pulse width (µs):

  uint32_t pulse_us = srf0x_read_us(&hsrfx);

• Get distance (cm):

  float dist_cm = srf0x_read_cm(&hsrfx);

Example

#include "main.h"
#include "srf0x.h"

extern TIM_HandleTypeDef htim2;

int main(void)
{
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();
    MX_TIM2_Init();
    
    // Enable DWT for microsecond delay
    CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
    DWT->CTRL    |= DWT_CTRL_CYCCNTENA_Msk;
    
    // Sensor handle
    SRF0X_HandleTypeDef sensor = {
        .TrigPort = GPIOA,
        .TrigPin  = GPIO_PIN_9,
        .EchoPort = GPIOA,
        .EchoPin  = GPIO_PIN_10,
        .htim     = &htim2
    };
    srf0x_init(&sensor);
    
    while (1)
    {
        float distance = srf0x_read_cm(&sensor);
        // Use distance (e.g., print via UART or display)
        HAL_Delay(100);
    }
}

API Reference

SRF0X_HandleTypeDef

Member	Type	Description
TrigPort	GPIO_TypeDef *	GPIO port for trigger
TrigPin	uint16_t	GPIO pin number for trigger
EchoPort	GPIO_TypeDef *	GPIO port for echo
EchoPin	uint16_t	GPIO pin number for echo
htim	TIM_HandleTypeDef *	Pointer to 1 MHz timer handle

Functions

void srf0x_init(SRF0X_HandleTypeDef *hsrf);

• Initialize sensor handle (peripherals must be ready).

void srf0x_trigger(SRF0X_HandleTypeDef *hsrf);

• Send a 10 µs pulse to trigger the sensor.

uint32_t srf0x_read_us(SRF0X_HandleTypeDef *hsrf);

• Measure echo pulse width, returns microseconds.

float srf0x_read_cm(SRF0X_HandleTypeDef *hsrf);

• Measure distance, returns centimeters (pulse_us / 58.0f).

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/NewFeature)
3. Commit your changes (git commit -m "Add NewFeature")
4. Push to branch (git push origin feature/NewFeature)
5. Open a pull request

Please ensure code is formatted and documented in the same style.

License

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

📞 Contact

For questions or suggestions, feel free to reach out via email: 📧 Alixahedi@gmail.com