# 系统函数

##  begin()

**函数原型：**

`void begin(bool LCDEnable=true, bool SDEnable=true, bool SerialEnable=true,bool I2CEnable=false);`

<!-- `fillScreen(color)` # for micropython -->

**功能：清串口缓冲区，设置串口波特率为 115200；初始化 LCD；初始化 SD 卡；初始化 I2C；设置按键 A 是睡眠唤醒按键。**

**函数实现**

```clike
void M5Stack::begin(bool LCDEnable, bool SDEnable, bool SerialEnable,bool I2CEnable) {

  // Correct init once
  if (isInited) return;
  else isInited = true;

  // UART
  if (SerialEnable) {
    Serial.begin(115200);
    Serial.flush();
    delay(50);
    Serial.print("M5Stack initializing...");
  }

  // LCD INIT
  if (LCDEnable) {
    Lcd.begin();
  }

  // TF Card
  if (SDEnable) {
    SD.begin(TFCARD_CS_PIN, SPI, 40000000);
  }

  // TONE
  // Speaker.begin();

  // Set wakeup button
  Power.setWakeupButton(BUTTON_A_PIN);

  // I2C init
  if(I2CEnable)
  {
    Wire.begin(21, 22);
  }

  if (SerialEnable) {
    Serial.println("OK");
  }
}

void M5Stack::update() {

  //Button update
  BtnA.read();
  BtnB.read();
  BtnC.read();

  //Speaker update
  Speaker.update();
}

```

**例程**

```clike
#include <M5Stack.h>

void setup() {
  M5.begin();
}
```

##  update()

**函数原型：**

`void update();`

<!-- `fillScreen(color)` # for micropython -->

**功能：读取按键 A, B, C 的状态。**

**函数实现**

```clike
void M5Stack::update() {

  //Button update
  BtnA.read();
  BtnB.read();
  BtnC.read();

  //Speaker update
  Speaker.update();
}
```

**例程**

```clike
#include <M5Stack.h>

void setup() {
  M5.begin();
}

void loop() {
  M5.update();
}
```

##  powerOFF()

?> 不推荐使用：请使用Power::deepSleep()

**函数原型：**

`void powerOFF();`

<!-- `fillScreen(color)` # for micropython -->

**功能：系统进入深度睡眠状态。**

**函数实现**

```clike
void M5Stack::powerOFF() {
  M5.Power.deepSleep();
}
```

**例程**

```clike
#include <M5Stack.h>

void setup() {
  M5.begin();
  M5.Lcd.println("This is software power off demo");
  M5.Lcd.println("Press the button A to power off.");
  M5.setWakeupButton(BUTTON_A_PIN);
}

void loop() {
  M5.update();
  if (M5.BtnA.wasPressed()) {
    M5.powerOFF();
  }
}
```