How to Interface HC-SR04 Ultrasonic Sensor with NXP i.MX93 Board Using GPIO and Timer Input Capture?

[Manjunathb]

I am working on a project involving distance measurement using the HC-SR04 Ultrasonic Sensor and the i.MX93 EVK (Evaluation Kit). I would like to understand the proper method to interface the sensor with the board.

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Requirements:

• Trigger the TRIG pin with a 10 µs high pulse.

• Measure the ECHO pin pulse width using GPIO + Timer Input Capture (or interruptCalculate the distance in centimeters based on the pulse width.

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Questions:

1. What GPIO or TPM/EPIT resources on the i.MX93 should I use for:

   • Outputting the TRIG pulse?

   • Capturing the ECHO signal (input capture or edge-triggered interrupt)?

2. How can I configure the GPIO pins for TRIG and ECHO using GPIO driver or IOMUX settings?

3. What is the recommended way to generate a 10 µs pulse on TRIG using i.MX93? Should I use a delay loop or a timer?

4. How can I use GPT (General Purpose Timer) or any available TPM/EPIT timer to:

   • Detect rising and falling edges on ECHO?

   • Measure the time between them (pulse width)?

5. Do I need to handle timer overflow manually or is there a built-in overflow counter?

6. Could you provide a sample initialization and ISR code snippet for:

   • TRIG pin setup and pulse generation.

   • ECHO pin edge detection and duration capture?

7. What is the recommended system clock configuration for precise timing (1 µs resolution)?

Thank you in advance!

i.MX93EVK TPMC-PEXPERT 

[Bio_TICFSL]

Hello,

To integrate the HC-SR04 ultrasonic sensor with an iMX9, you need to connect the sensor pins to the iMX9's GPIO pins. The HC-SR04 has four pins: VCC (5V), GND, TRIG, and ECHO. You'll need to connect VCC to the iMX9's 5V power supply, GND to ground, TRIG to a GPIO pin that we'll configure as an output, and ECHO to another GPIO pin that we'll configure as an input. Then, using code, you'll generate a pulse on the TRIG pin and measure the time it takes to receive a pulse on the ECHO pin to calculate the distance. Connecting the HC-SR04 to the iMX9: VCC: Connect it to the iMX9's 5V power supply. GND: Connect it to the iMX9's ground. TRIG: Connect it to a GPIO pin on the iMX9 that will be configured as an output. ECHO: Connect it to a GPIO pin on the iMX9 that will be configured as an input.

Example code (pseudo-code): C

#define TRIG_PIN 2 // Ejemplo, pin GPIO 2
#define ECHO_PIN 3 // Ejemplo, pin GPIO 3

// Función para calcular la distancia
int distancia() {
// 1. Generar pulso de disparo (10 us)
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);

// 2. Medir el tiempo del pulso de eco
long duration = pulseIn(ECHO_PIN, HIGH);

// 3. Calcular la distancia (velocidad del sonido: 343 m/s o 0.0343 cm/us)
int distance = duration * 0.0343 / 2;
return distance;
}

void setup() {
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
Serial.begin(115200); // Iniciar comunicación serial
}

void loop() {
int dist = distancia();
Serial.print("Distancia: ");
Serial.print(dist);
Serial.println(" cm");
delay(100); // Retardo de 100ms
}

 TRIG_PIN and ECHO_PIN define the iMX9 GPIO pins connected to the sensor. The distance() function calculates the distance: First, it generates a short pulse (10 ms) on the TRIG pin to start the measurement. Then, it uses the pulseIn() function to measure the pulse duration on the ECHO pin (the time it takes for the echo to return).

Finally, it calculates the distance using the speed of sound. setup() initializes the pins as output and input, and begins serial communication. loop() calls the distance() function, prints the result to the serial console, and waits 100 ms before repeating the process. Considerations: Voltage: The HC-SR04 operates at 5 V, while some iMX9 pins may be 3.3 V. You may need a logic level converter or a voltage regulator to ensure compatibility. Libraries: On platforms like Arduino, there are libraries that simplify interaction with the HC-SR04. If you're using an operating system like Linux on the iMX9, you may need to create your own functions or search for iMX9-specific libraries. Accuracy: The accuracy of the HC-SR04 may vary depending on environmental conditions (temperature, humidity) and the surface of the object. Interference: Avoid interference from other nearby ultrasonic devices.

Regards

[Manjunathb]

Thank you for your reply!