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This gist is part of the article http://codelectron.com/measure-distance-ultrasonic-sensor-pi-hc-sr04/
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| import RPi.GPIO as GPIO | |
| import pyaudio | |
| from numpy import linspace,sin,pi,int16 | |
| from luma.core.interface.serial import i2c | |
| from luma.core.render import canvas | |
| from luma.oled.device import ssd1306, ssd1325, ssd1331, sh1106 | |
| import time | |
| RATE = 4400 | |
| FREQ = 261.6 | |
| GPIO.setmode(GPIO.BCM) | |
| GPIO_TRIGGER = 23 | |
| GPIO_ECHO = 24 | |
| GPIO.setup(GPIO_TRIGGER, GPIO.OUT) | |
| GPIO.setup(GPIO_ECHO, GPIO.IN) | |
| serial = i2c(port=1, address=0x3C) | |
| device = ssd1306(serial, rotate=0) | |
| pa = pyaudio.PyAudio() | |
| s = pa.open(output=True, | |
| channels=2, | |
| rate=RATE, | |
| format=pyaudio.paInt16, | |
| output_device_index=2) | |
| def distance(): | |
| GPIO.output(GPIO_TRIGGER, True) | |
| # set Trigger after 0.01ms to LOW | |
| time.sleep(0.00001) | |
| GPIO.output(GPIO_TRIGGER, False) | |
| StartTime = time.time() | |
| StopTime = time.time() | |
| while GPIO.input(GPIO_ECHO) == 0: | |
| StartTime = time.time() | |
| # save time of arrival | |
| while GPIO.input(GPIO_ECHO) == 1: | |
| StopTime = time.time() | |
| # time difference between start and arrival | |
| TimeElapsed = StopTime - StartTime | |
| # multiply with the sonic speed (34300 cm/s) | |
| # and divide by 2, because there and back | |
| distance = (TimeElapsed * 34300) / 2 | |
| return distance | |
| def note(freq, len, amp=5, rate=44100): | |
| t = linspace(0,len,len*rate) | |
| data = sin(2*pi*freq*t)*amp | |
| return data.astype(int16) # two byte integers | |
| if __name__ == '__main__': | |
| try: | |
| while True: | |
| dist = distance() | |
| print ("Measured Distance = %.1f cm" % dist) | |
| if ( dist > 20 ): | |
| FREQ=261 | |
| elif (dist > 10): | |
| FREQ=350 | |
| else: | |
| FREQ=600 | |
| tone = note(FREQ, 1, amp=10000, rate=RATE) | |
| with canvas(device) as draw: | |
| draw.rectangle(device.bounding_box, outline="white", fill="black") | |
| draw.text((10, 40), "Distance = %.1f cm"%dist, fill="white") | |
| s.write(tone) | |
| #time.sleep(0.20) | |
| # Reset by pressing CTRL + C | |
| except KeyboardInterrupt: | |
| print("Measurement stopped by User") | |
| GPIO.cleanup() |
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