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用蜂鸣器播放音乐

1. 编程蜂鸣器

  1. 首先从machine库导入引脚和PWM，从utime库导入sleep. 
from machine import Pin, PWM
from utime import sleep
  1. 初始化PWM(也就是脉宽调制)到管脚22，并分配它为变量buzzer。
buzzer = PWM(Pin(22))
  1. 给变量buzzer分配一个频率属性，选择10到12,000之间的数值，数值越大音调越高，我们可以设定为500. 
buzzer.freq(500)
  1. 将蜂鸣器对象的duty_u16属性设置为1000，这就能让蜂鸣器尽可能地响。更低的值更安静，0根本没有声音。
buzzer.duty_u16(1000)
  1. Set a 1 second delay and then set duty to 0 so that the sound stops. If you don’t do this, the buzz will continue, even after the program is finished executing.
sleep(1)
buzzer.duty_u16(0)

Your final code for this simple test should look like this. 

from machine import Pin, PWM
from utime import sleep
 
buzzer = PWM(Pin(15))
buzzer.freq(500)
buzzer.duty_u16(1000)
sleep(1)
buzzer.duty_u16(0)

2. 使用Pico驱动蜂鸣器播放音乐

Because you can use different frequencies, you can create a full array of musical notes. There are a few lists of musical note frequencies online and many of them trace back to Brett Hagman’s Arduino tone library on Github. We’ll use these values to create a list we can use to play any song early in our code.

  1. Import the necessary libraries and initialize PWM on pin 15.
from machine import Pin, PWM
from utime import sleep
 
buzzer = PWM(Pin(22))
  1. Create a dictionary called notes with the following values. 
tones = {
"B0": 31,
"C1": 33,
"CS1": 35,
"D1": 37,
"DS1": 39,
"E1": 41,
"F1": 44,
"FS1": 46,
"G1": 49,
"GS1": 52,
"A1": 55,
"AS1": 58,
"B1": 62,
"C2": 65,
"CS2": 69,
"D2": 73,
"DS2": 78,
"E2": 82,
"F2": 87,
"FS2": 93,
"G2": 98,
"GS2": 104,
"A2": 110,
"AS2": 117,
"B2": 123,
"C3": 131,
"CS3": 139,
"D3": 147,
"DS3": 156,
"E3": 165,
"F3": 175,
"FS3": 185,
"G3": 196,
"GS3": 208,
"A3": 220,
"AS3": 233,
"B3": 247,
"C4": 262,
"CS4": 277,
"D4": 294,
"DS4": 311,
"E4": 330,
"F4": 349,
"FS4": 370,
"G4": 392,
"GS4": 415,
"A4": 440,
"AS4": 466,
"B4": 494,
"C5": 523,
"CS5": 554,
"D5": 587,
"DS5": 622,
"E5": 659,
"F5": 698,
"FS5": 740,
"G5": 784,
"GS5": 831,
"A5": 880,
"AS5": 932,
"B5": 988,
"C6": 1047,
"CS6": 1109,
"D6": 1175,
"DS6": 1245,
"E6": 1319,
"F6": 1397,
"FS6": 1480,
"G6": 1568,
"GS6": 1661,
"A6": 1760,
"AS6": 1865,
"B6": 1976,
"C7": 2093,
"CS7": 2217,
"D7": 2349,
"DS7": 2489,
"E7": 2637,
"F7": 2794,
"FS7": 2960,
"G7": 3136,
"GS7": 3322,
"A7": 3520,
"AS7": 3729,
"B7": 3951,
"C8": 4186,
"CS8": 4435,
"D8": 4699,
"DS8": 4978
}
  1. Create a list (aka array) of notes for your song. Use the letter P to represent pauses in the music. Each note should be in quotation marks. 
song = ["E5","G5","A5","P","E5","G5","B5","A5","P","E5","G5","A5","P","G5","E5"]

Hat tip to the folks on this thread for sharing the notes for this famous riff.

  1. Create a function called playtone that will take any frequency and play it at full volume. 
def playtone(frequency):
    buzzer.duty_u16(1000)
    buzzer.freq(frequency)
  1. Create a function called bequiet that will silence the buzzer by change duty_u16 to 0. 
def bequiet():
    buzzer.duty_u16(0)
  1. Create a function called playsong that you will use to iterate through the array of notes and play each or pause when it sees P. 
def playsong(mysong):
    for i in range(len(mysong)):
        if (mysong[i] == "P"):
            bequiet()
        else:
            playtone(tones[mysong[i]])
        sleep(0.3)
    bequiet()

Here’s what’s going on here. First, we create a for loop that iterates through all the values in the mysong array. If the value is equal to P, it triggers be quiet and, if not, it triggers playtone. Note that playtone requires a numeric frequency value so we have to get the number for each note from the tones list. If we just playtone(mysong[i]), it will fail because it will try to play the string “E5,” instead of frequency 659, which is the integer it needs.

For each tone or pause, the system maintains state for 0.3 seconds of sleep. If you want a faster tempo, you can lower that time. If you want a slower tempo, increase it.

  1. Trigger the playsong function with the song parameter.
playsong(song)

When you run this code, you will hear your buzzer play a familiar melody. Here’s what the complete code should look like: 

from machine import Pin, PWM
from utime import sleep
buzzer = PWM(Pin(15))
 
tones = {
"B0": 31,
"C1": 33,
"CS1": 35,
"D1": 37,
"DS1": 39,
"E1": 41,
"F1": 44,
"FS1": 46,
"G1": 49,
"GS1": 52,
"A1": 55,
"AS1": 58,
"B1": 62,
"C2": 65,
"CS2": 69,
"D2": 73,
"DS2": 78,
"E2": 82,
"F2": 87,
"FS2": 93,
"G2": 98,
"GS2": 104,
"A2": 110,
"AS2": 117,
"B2": 123,
"C3": 131,
"CS3": 139,
"D3": 147,
"DS3": 156,
"E3": 165,
"F3": 175,
"FS3": 185,
"G3": 196,
"GS3": 208,
"A3": 220,
"AS3": 233,
"B3": 247,
"C4": 262,
"CS4": 277,
"D4": 294,
"DS4": 311,
"E4": 330,
"F4": 349,
"FS4": 370,
"G4": 392,
"GS4": 415,
"A4": 440,
"AS4": 466,
"B4": 494,
"C5": 523,
"CS5": 554,
"D5": 587,
"DS5": 622,
"E5": 659,
"F5": 698,
"FS5": 740,
"G5": 784,
"GS5": 831,
"A5": 880,
"AS5": 932,
"B5": 988,
"C6": 1047,
"CS6": 1109,
"D6": 1175,
"DS6": 1245,
"E6": 1319,
"F6": 1397,
"FS6": 1480,
"G6": 1568,
"GS6": 1661,
"A6": 1760,
"AS6": 1865,
"B6": 1976,
"C7": 2093,
"CS7": 2217,
"D7": 2349,
"DS7": 2489,
"E7": 2637,
"F7": 2794,
"FS7": 2960,
"G7": 3136,
"GS7": 3322,
"A7": 3520,
"AS7": 3729,
"B7": 3951,
"C8": 4186,
"CS8": 4435,
"D8": 4699,
"DS8": 4978
}
 
song = ["E5","G5","A5","P","E5","G5","B5","A5","P","E5","G5","A5","P","G5","E5"]
 
def playtone(frequency):
    buzzer.duty_u16(1000)
    buzzer.freq(frequency)
 
def bequiet():
    buzzer.duty_u16(0)
 
def playsong(mysong):
    for i in range(len(mysong)):
        if (mysong[i] == "P"):
            bequiet()
        else:
            playtone(tones[mysong[i]])
        sleep(0.3)
    bequiet()
playsong(song)