在Ubuntu Mate（Raspberry Pi 3）和python中使用多個超聲傳感器

Question

我試圖將三個獨立的超聲波傳感器（HC-SR04）連接到運行Ubuntu Mate的Raspberry Pi。 目的是從傳感器讀取輸入並將其發送到LAMP驅動的服務器。 該系統可以在一個傳感器上正常運行，但是我不確定如何將多個傳感器連接到系統。 目前，我正在使用的代碼如下：

import RPi.GPIO as GPIO
import time

#GPIO Mode (BOARD / BCM)
GPIO.setmode(GPIO.BCM)

#set GPIO Pins
GPIO_TRIGGER = 16
GPIO_ECHO = 21
GPIO_ECHO2 = 24

#set GPIO direction (IN / OUT)
GPIO.setup(GPIO_TRIGGER, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)
GPIO.setup(GPIO_ECHO2, GPIO.IN)


#MySQL
import MySQLdb

dbConn = MySQLdb.connect("127.0.0.1","root","","test") or die ("could not connect to db")
cursor = dbConn.cursor()

def distance1():
    # set Trigger to HIGH
    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()

    # save StartTime
    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 distance1

    def distance2():
            # set Trigger to HIGH
            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()

            # save StartTime
            while GPIO.input(GPIO_ECHO2) == 0:
                StartTime = time.time()

            # save time of arrival
            while GPIO.input(GPIO_ECHO2) == 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 distance2



    if __name__ == '__main__':
            try:
                while True:
                    dist = distance1()
                    if distance1()  < 20:
                        print ("1")
                        cursor.execute("INSERT INTO TILA (anturi, status) values (1, 0)")
                        dbConn.commit()
                    else:
                        print ("0")
                        cursor.execute("INSERT INTO TILA (anturi, status) values (1, 1)")
                        dbConn.commit()
                    time.sleep(1)
                        # Reset by pressing CTRL + C
            except KeyboardInterrupt:
                    print("Measurement stopped by User")
                    cursor.close()
                    GPIO.cleanup()


                    if __name__ == '__main__':
                        try:
                            while True:
                                dist = distance2()
                                if distance2()  < 20:
                                    print ("1")
                                    cursor.execute("INSERT INTO TILA (anturi, status) values (1, 0)")
                                    dbConn.commit()
                                else:
                                    print ("0")
                                    cursor.execute("INSERT INTO TILA (anturi, status) values (1, 1)")
                                    dbConn.commit()
                                time.sleep(1)

                # Reset by pressing CTRL + C
                        except KeyboardInterrupt:
                                print("Measurement stopped by User")
                                cursor.close()
                                GPIO.cleanup()

現在，此代碼確實可以在終端中運行，但是不起作用。 它可以在一個傳感器上正常工作，但是在我更改代碼以包含兩個“回聲”和“距離”后，它停止工作。 這是我第一次使用python，我知道這段代碼可能有幾個錯誤。 如果有人能告訴我我是否走上了正確的道路以及如何從這里繼續，我將不勝感激！

Answer 1

您有太多重復的代碼。 如果要更改代碼以便可以檢查多個距離，則應制作一個通用distance函數，該函數將傳感器作為參數並進行檢查。

def distance(gpio_echo):
    # set Trigger to HIGH
    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()

    # save StartTime
    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
    dist = (TimeElapsed * 34300) / 2

    return dist

然后，您可以為所有傳感器多次調用此函數：

if __name__ == '__main__':

    sensors_to_test = [GPIO_ECHO, GPIO_ECHO2]

    try:
        while True:
            for sensor in sensors_to_test:
                dist = distance(sensor)
                if dist < 20:
                    print ("1")
                    cursor.execute("INSERT INTO TILA (anturi, status) values (1, 0)")
                    dbConn.commit()
                else:
                    print ("0")
                    cursor.execute("INSERT INTO TILA (anturi, status) values (1, 1)")
                    dbConn.commit()
            time.sleep(1)

    except KeyboardInterrupt:
        # Reset by pressing CTRL + C
        print("Measurement stopped by User")
        cursor.close()
        GPIO.cleanup()

---

進行編程時，如果要多次執行某些操作，則請勿多次復制和粘貼代碼。 有一些稱為循環的編程構造。 在這里，我們使用一個for循環：

for sensor in sensors_to_test:
    dist = distance(sensor)

始終將邏輯封裝到接受參數的函數中，並使用它們而不是復制代碼！

---

PS：在python中，我們從不使用if __name__ == '__main__':在文件中多次使用，並且僅在可執行python腳本的末尾使用。 它不是C或Java中的主要功能。 這只是一個巧妙的技巧，因此當您從命令行調用python腳本中的代碼時，該代碼將被執行。 如果您想了解更多信息，請查看此問題： __name__ ==“ __main__”怎么辦？