51 microcontroller CO2 detection display program analysis

This is a 51 microcontroller CO2 detection and display program data. The T (TXD) of the carbon dioxide sensor MH-Z19 module is connected to the RXD of the microcontroller, R (RXD) is connected to the TXD of the microcontroller, V+ is connected to the 5v positive pole of the microcontroller, and V- is connected to the ground of the microcontroller ( Serial TTL communication requires connecting these four lines); the measurement voltage is 5V; the microcontroller model is STC89C52, the liquid crystal display model is LCD1602, and the circuit connection is in accordance with the test diagram; the serial communication baud rate is 9600, pay attention to the crystal oscillator if it is 11.0592M, otherwise it will Causes communication failure; the sensor needs to warm up for 3 minutes when powered on.

#include "reg52.h"

#include "stdio.h"

#include "intrins.h"

#include "lcd1602.H"

#define uchar unsigned char

#define uint unsigned int

#define ulong unsigned long

uchar code tab［9］={0xff，0x01，0x86，0x00，0x00，0x00，0x00，0x00，0x79};

uchar date[]={0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

void delayms(uint xms)

{

uint x, y;

for（x=xms;x》0;x--）

for(y=110;y》0;y--);

}

void send(uchar dat) //Send one byte

{

SBUF=dat;

while(!TI);

TI=0;

}

void main(void)

{

uint tmp;

uchar i;

TMOD=0x20; // T1 timing mode 2

SCON=0x40;//Serial working mode 1

PCON=0x00; //Do not double

TH1=TL1=0xfd; //Assign an initial value to timer 1 to ensure the baud rate is 9600

TR1=1; //Open timer 1

REN=1; //Allow serial port reception

init_1602(); //LCD initialization

delayms(10);

ES=1; //Open serial port interrupt

EA=1; //Enable total interrupt

while(1)

{

for（i=0;i《9;i++） //Send data to co2 sensor

{

send(tab[i]);

}

delayms(1000); //Delay one second to refresh the measured data

tmp=date［2］*256+date［3］; //Calculate the co2 concentration value

if(tmp》9999)

tmp=0;

WRITE_LCD1602_COM(0x80+8);

if（（tmp/1000）》0）

WRITE_LCD1602_DAT(LCD1602_Table[tmp/1000]);

else WRITE_LCD1602_DAT(' ');

WRITE_LCD1602_DAT(LCD1602_Table[tmp00/100]);

WRITE_LCD1602_DAT(LCD1602_Table[tmp0/10]);

WRITE_LCD1602_DAT(LCD1602_Table[tmp]);

}

}

void serial()interrupt 4 //Serial port interrupt service function

{

static uchar j;

ES=0; //Disable interrupts

if(!RI);

RI=0; //Clear receiving completion flag

date［j］=SBUF;

if（date［0］==0xff） //Judge that the first bit received is the data sent by the sensor.

j++;

else

j=0;

if (j==9) //Receive 9 bytes of data sent by the sensor

j=0;

ES=1; //Allow serial port interrupt

}

///////////////////////////////////////////////////// ////////////////////////////////////////////////

lcd1602.H：

#define uchar unsigned char

#define uint unsigned int

sbit RS=P2^5;

sbit RW=P2^6;

sbit EN=P2^7;

uchar LCD1602_Table［]=“0123456789”;

//LCD1602 display ruler//0123456789abcdef

uchar code DIS_TIM［16］ = {“ PPM= ”}; //Display temperature and humidity

uchar code DIS_STA［16］ = {“ Test is OK! ”}; //

uchar code DIS［16］ = {“alarm ppm”}; //

extern void delayms(uint xms);

void WRITE_LCD1602_DAT(uchar date)

{

EN=0;

RS=1;

P0=date;

EN=1;

delayms(2);

EN=0;

}

void WRITE_LCD1602_COM(uchar date)

{

EN=0;

RS=0;

P0=date;

EN=1;

delayms(2);

EN=0;

}

void init_1602()

{

unsigned char i;

RW=0;

WRITE_LCD1602_COM(0x38);

WRITE_LCD1602_COM(0x0c);

WRITE_LCD1602_COM(0x06);

WRITE_LCD1602_COM(0x01);

WRITE_LCD1602_COM(0x80);

for（i=0;i《8;i++）

WRITE_LCD1602_DAT(DIS_TIM［i］);

}