Raspberry Pi Ultrasonic Sensor (HC-SR04) Control

# 1. Ultrasonic Sensor Test Circuit Configuration  ( HC-SR04 ultrasonic sensor 1EA, 1KΩ resistor 1EA Echo connection, 2KΩ resistor 1EA GND connection ) Trig: GPIO 17 connection, Echo: GPIO 18 connection Caution: When a High level signal is generated on the echo pin, 5V is transmitted. However, since the Raspberry Pi operates at 3.3V, the voltage must be stepped down to 3.3V using 1KΩ and 2KΩ resistors to prevent Raspberry Pi damage. For code writing and execution methods, refer to the "**Raspberry Pi GPIO Port (LED, Button) Control**" guide. **2. Ultrasonic Sensor Test Python Code** The distance to an object is calculated by measuring the time it takes for an ultrasonic wave to bounce off an object and return. ```python import RPi.GPIO as GPIO # Use functions defined in RPi.GPIO as GPIO import time # time module GPIO.setmode(GPIO.BCM) # Use BCM nomenclature for GPIO names GPIO.setup(17, GPIO.OUT) # Trig=17 ultrasonic signal transmission pin number designation and output specification GPIO.setup(18, GPIO.IN) # Echo=18 ultrasonic reception pin number designation and input specification print "Press SW or input Ctrl+C to quit" # Display message on screen try: while True: GPIO.output(17, False) time.sleep(0.5) GPIO.output(17, True) # Output a 10us pulse. time.sleep(0.00001) # This pulse in Python will actually be around 100us GPIO.output(17, False) # However, the HC-SR04 sensor accepts this error while GPIO.input(18) == 0: # Set the moment when pin 18 turns OFF as the start time start = time.time() while GPIO.input(18) == 1: # Set the moment when pin 18 turns ON again as the reflected wave reception time stop = time.time() time_interval = stop ? start # Calculate distance from ultrasonic reception time distance = time_interval * 17000 distance = round(distance, 2) print "Distance => ", distance, "cm" except KeyboardInterrupt: # When Ctrl-C is input GPIO.cleanup() # Clear GPIO related settings Print "bye~" ``` # 3. Ultrasonic Sensor Test C Code ```c #include // Include stdio.h file (to use printf()) #include // Include wiringPi.h file int main(void ) { Float distance, start, stop; wiringPiSetup(); // GPIO pin numbering based on wiringPi standard pinMode(0, OUTPUT); // wiringPi GPIO 0 = Python(BCM) 17 pinMode(1, INPUT); // wiringPi GPIO 1 = Python(BCM) 18 while(1) { digitalWrite(0,0); // Output wiringPi pin 0 to Low digitalWrite(0,1); // Output wiringPi pin 0 to High delayMicroseconds(10); // Pause for 10 microseconds digitalWrite(0,0); while(digitalRead(1) == 0) // When wiringPi pin 1 is Low start = micros(); // Save microseconds while(digitalRead(1) == 1) // When wiringPi pin 1 is High stop = micros(); // Save microseconds distance = (stop ? start) / 58; // Derive distance using the time difference printf("Distance=> %2f cm \n",distance); delay(1000); } return 0; } ```