#include <Arduino.h>

 #include <Wire.h>

 #include <LiquidCrystal_I2C.h>

 float pm25 = ;

 #define DATALEN 7

 LiquidCrystal_I2C lcd(0x3F,,);  // set the LCD address to 0x27 for a 16 chars and 2 line display

 void setup() {

   // put your setup code here, to run once:

   Serial.begin();

   lcd.init();                      // initialize the lcd

   // Print a message to the LCD.

   lcd.backlight();

   lcd.print("PM2.5");

 }

 void ProcessSerialData()//读取PM2.5的数据。

 {

   uint8_t mData = ;

   uint8_t i = ;

   uint8_t mPkt[DATALEN] = {};

   int mCheck = ;

   while (Serial.available() > )

   {

     mData = Serial.read();

     delay();//wait until packet is received

     if(mData == 0xAA)//head1 ok

      {

         mPkt[] =  mData;

         mData = Serial.read();

         {

           for(int i=;i < DATALEN;i++)//data recv and crc calc

           {

             mPkt[i] = Serial.read();

             Serial.print(mPkt[i],HEX);

            Serial.print("---");

              delay();

           }

           delay();

           Serial.println();

     //      Serial.println(mPkt[3]*256+mPkt[2]);

  //         Serial.print(mPkt[2]);

 //          Serial.println("    ");

  //         Serial.print("---");

 //          Serial.print(mPkt[5]);

           if(mPkt[DATALEN-] == 0xFF)

           {

             pm25 = (mPkt[]<<)|mPkt[];

              Serial.println(float(pm25/));

              lcd.setCursor(,);

              lcd.print(float(pm25/));

             Serial.flush();

             return;

           }

         }

      }

    }

 }

 void loop() {

   ProcessSerialData();

 }