STM32 with HC-SR04 Ultrasonic Sensor

Project Description

This project demonstrates how to interface an HC-SR04 ultrasonic distance sensor with an STM32F103C6 microcontroller using the Timer Input Capture mode for precise echo pulse measurement.

The HC-SR04 sensor operates by emitting 40 kHz ultrasound pulses and measuring the time-of-flight of the returning echo. By leveraging STM32’s advanced TIM1 input capture, we can measure the echo pulse width accurately, enabling reliable distance calculation. Measurement results are sent to a UART terminal in real-time for monitoring.

Working Principle

• The STM32 sets TRIG High for 10 µs to start a measurement.
• The sensor emits an ultrasonic burst at 40 kHz.
• The ECHO pin goes High and stays High until the echo is received.
• The STM32’s Timer Input Capture measures the High pulse duration.
• Distance is calculated using:

HC-SR04 Pinout

• VCC → +5V supply
• GND → Ground
• TRIG → Input pin to initiate measurement (10 µs pulse)
• ECHO → Output pin, pulse width proportional to distance

STM32CubeMX Setup

• MCU Selection: STM32F103C6 (16 MHz clock)
• GPIO Configuration:

- PA10 → Output (TRIG)

- PA8 → Input Capture (ECHO)

• TIM1 Configuration:

- Channel 1 → Input Capture Direct Mode

- Prescaler = 16-1

Counter Period = 65535

• UART1 Configuration:

- Baud Rate = 115200

- Word Length = 8 bits

- No parity

• Generate initialization code in STM32CubeIDE.

STM32CubeIDE Implementation

Key Functions

• Trigger Pulse Generation

- void HCSR04_Trigger(void);

- Sends a 10 µs HIGH pulse on TRIG to start measurement.

• Input Capture Callback

- void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim);

- Captures rising and falling edges of the ECHO pin to compute pulse width.

• Main Loop

- HCSR04_Trigger();

- HAL_UART_Transmit(&huart1, (uint8_t*)msg,

- sprintf(msg, "Distance: %d cm\r\n", Distance), 100);

- Periodically triggers the sensor and prints measured distance over UART.

Proteus Simulation

Components

• STM32F103C6 microcontroller
• HC-SR04 ultrasonic sensor (or SRF04 equivalent)
• Virtual Terminal (UART, 115200 baud)

Connections

• PA10 → TRIG
• PA8 → ECHO
• PA9 (UART TX) → Virtual Terminal

Steps

• Load the generated .hex file into STM32 in Proteus.
• Adjust the distance parameter in the SRF04/HC-SR04 component.
• Monitor distance output values in the Virtual Terminal.

That’s all!

If you have any questions or suggestions don’t hesitate to leave a comment below