Create pwm.md

docs/zh_CN/api/pwm.md

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+# PWM
+
+*PWM用于产生模拟信号驱动舵机或蜂鸣器*
+
+## ledcSetup()
+
+**函数原型：**
+
+<mark>void ledcSetup(uint8_t channel, double freq, uint8_t resolution_bits);</mark>
+
+**功能：设置PWM通道,频率和分辨率。**
+
+## ledcAttachPin()
+
+**函数原型：**
+
+<mark>void ledcAttachPin(uint8_t pin, uint8_t channel);</mark>
+
+**功能：将 LEDC 通道绑定到指定 IO 口上以实现输出**
+
+## ledWrite()
+
+**函数原型：**
+
+<mark>void ledcWrite(uint8_t channel, uint32_t duty);</mark>
+
+**功能：向channel通道写入duty%占空比。**
+
+**例程：**
+```arduino
+#include <M5StickC.h>
+int freq = 1800;
+int channel = 0;
+int resolution_bits = 8;
+int buzzer = 2;
+
+void setup() {
+  M5.begin();
+  ledcSetup(channel, freq, resolution_bits);
+  ledcAttachPin(buzzer, channel);
+}
+void loop() {
+    ledcWrite(channel, 128);
+    delay(1000);
+    ledcWrite(channel, 0);
+    delay(1000);
+}
+```