（arduino框架）ESP32学习笔记1 如何输出可调频率和占空比的pwm波

（arduino框架）ESP32学习笔记1: 如何输出可调频率和占空比的pwm波

（1）esp32使用pwm波的函数在esp32-hal-ledc.h文件当中定义，其中共有16个通道可配置

//channel 0-15 resolution 1-16bits freq limits depend on resolution
		//初始化设置通道频率和分辨率
double      ledcSetup(uint8_t channel, double freq, uint8_t resolution_bits);
		//设置通道的占空比
void        ledcWrite(uint8_t channel, uint32_t duty);
		//设置通道的频率
double      ledcWriteTone(uint8_t channel, double freq);
		//输出需要的音阶
double      ledcWriteNote(uint8_t channel, note_t note, uint8_t octave);
		//读取某个通道的占空比
uint32_t    ledcRead(uint8_t channel);
		//读取通道的频率
double      ledcReadFreq(uint8_t channel);
		//将通道和引脚绑定
void        ledcAttachPin(uint8_t pin, uint8_t channel);
		//解绑通道和引脚的关系
void        ledcDetachPin(uint8_t pin);

（2）其中ledcWriteNote函数为输出一些音阶，可以接上蜂鸣器发出一些简单的音频， 函数如下：

double ledcWriteNote(uint8_t chan, note_t note, uint8_t octave){
    const uint16_t noteFrequencyBase[12] = {
    //   C        C#       D        Eb       E        F       F#        G       G#        A       Bb        B
        4186,    4435,    4699,    4978,    5274,    5588,    5920,    6272,    6645,    7040,    7459,    7902
    };
 
    if(octave > 8 || note >= NOTE_MAX){
        return 0;
    }
    double noteFreq =  (double)noteFrequencyBase[note] / (double)(1 << (8-octave));
    return ledcWriteTone(chan, noteFreq);
}

（3）代码：在Arduino环境下用esp32输出pwm波（基于platform io）

所用开发板是安信可的NodeMCU-32S核心开发板

代码：

#include <Arduino.h>
#define LED 2
#define LED_OFF digitalWrite(LED,High)    //关灯
#define LED_ON    digitalWrite(LED, LOW)  //开灯
int freq = 2000;    //设置PWM波的频率
int channel = 0;    //设置通道,共16个通道，0~15
int resolution = 10; //分辨率，取值0~20 duty的最大值为 2^resolution-1
bool val = 0;
void setup() {
  // put your setup code here, to run once:
  ledcSetup(channel,freq,resolution);   //设置通道0
  ledcAttachPin(LED,channel);           //将通道0和gpio_pin连接起来
}

void loop() {
  // put your main code here, to run repeatedly:
  // led逐渐变暗
 for (int  i = 0; i < 1023; i=i+5)
 {
   ledcWrite(channel,i);
   delay(5);
 }
 // led逐渐变亮
 for (int  i = 1023; i >= 0 ; i=i-5)
 {
   ledcWrite(channel,i);
   delay(5);
 }
}