0-99V digital voltmeter made with STC12C2052AD microcontroller

The 0-99V digital voltmeter made with STC12C2052AD microcontroller comes from Digital Home_abenyao. I think this circuit is quite useful. The principle is simple. It directly uses the AD with STC12C2052AD microcontroller. The digital tube uses a four-digit common anode digital tube. There is a little jump after the decimal point. The circuit is built on a breadboard. The reference voltage is generated by TL431. The following is a real picture:

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0-99V digital voltmeter source program made with STC12C2052AD microcontroller
First published by Digital Home. ID: abenyao
P1.6 port is 0-5V analog input terminal, P1.5 port is connected to 2.5V reference power supply output by TL431l, 4-bit serial LED digital tube display
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#include  //MCU header file
#include  //51 basic operations (including _nop_ empty function)
#define uchar unsigned char
#define uint unsigned int
#define LEDBus P3
//a3.0-b3.1-c3.2-d3.3-e3.4-f3.5-g3.7-dp1.0
#define ON 1 //define 0 as on
#define OFF 0 //define 1 to turn off


sbit ge=P1^4; //bit selection
sbit shi=P1^3; //Tens bit selection
sbit bai=P1^2; //hundreds digit selection
sbit qian=P1^1; //Thousands digit selection
sbit db=P1^0;
char d[5];
uint R,M,N; //If defined as uchar type, it can only display values ​​below 2.5V
uchar code LEDTab[]={0xc0,0xf9,0x64,0x70,0x59,0x52,0x42,0xf8,0x40,0x58};
/****************************************************** ****************
Function name: millisecond CPU delay function
Call: delay (?);
Parameter: 1~65535 (parameter cannot be 0)
Return value: None
Result: The CPU usage delay is the same as the parameter value in milliseconds
Note: When applied to 1T MCU, i<600; when applied to 12T MCU, i<125
/****************************************************** *******************/
void delay(uint t)
{
uint i; //define variables
for(;t>0;t--) //If t is greater than 0, t minus 1 (outer loop)
  for(i=600;i>0;i--); //i is equal to 124, if i is greater than 0, i minus 1
}
/****************************************************** ******************
Function name: ADC initialization and 8-bit A/D conversion function
Return value: 8-bit ADC data
Result: Read the A/D conversion value of the specified ADC interface and return the value
Note: Applicable to STC12C2052AD series MCU (must use STC12C2052AD.h header file)
*************************************************** *******************/
uchar Read (uchar CHA) {
uchar AD_FIN=0; //Store A/D conversion flag; if this variable is defined outside the function, the display of continuously changing analog quantity cannot be obtained
/******The following is the ADC initialization program********************************/
    CHA &= 0x07; //Select one of the 8 interfaces of ADC (0000 0111 clear the high 5 bits)
    ADC_CONTR = 0x60; //ADC conversion speed (0XX0 0000, XX controls the speed, please set according to the data sheet)
    _nop_();
    ADC_CONTR |= CHA; //Select the current A/D channel
    _nop_();
    ADC_CONTR |= 0x80; //Start A/D power supply
    delay(1); //Let the input voltage reach stability (1ms is enough?
/******The following is the ADC execution program********************************/
    ADC_CONTR |= 0x08; //Start A/D conversion (0000 1000 ADCS = 1)
    _nop_();
    _nop_();
    _nop_();
    _nop_();
    while (AD_FIN ==0){ //Wait for A/D conversion to end
    AD_FIN = (ADC_CONTR & 0x10); //0001 0000 Test whether A/D conversion is finished
    }
    ADC_CONTR &= 0xE7; //1111 0111 clear ADC_FLAG bit, turn off A/D conversion,
return (ADC_DATA); //Return A/D conversion result (8 bits)
}
/****************************************************** *****************
Displays the function conversion function:
M = analog sampling value, N = reference voltage source sampling value (2.5V in this example), R = analog input value (to be displayed)
N=256*2.5/Vcc; after deformation, Vcc=256*2.5/N; Substitute M=256*R/Vcc; get M=R*N/2.5; after deformation, R=M*2.5/N
1.105 is the voltage divider ratio at the input.
*************************************************** ****************/
void transfer(void){
M=Read(6); //P1.6 port analog conversion
N=Read(5); //P1.5 port 2.5V reference voltage source sampling (conversion)
R=((M*2.5)/N)*1.105*1000; //Convert the input analog quantity and amplify it 1000 times;
/***The following is a 3-digit display conversion***/
d[3]=R/1000;
R=R%1000;
d[2]=R/100;
R=R%100;
d[1]=R/10;
d[0]=R%10;
}
/**********Display function (not optimized)****************************************************/
void xian_shi (void)
{
LEDBus=LEDTab[d[0]]; //Send the unit digit to the digital tube for display
ge=ON; //Open the unit digit selection
delay(2); //1 means display for 1 millisecond, 0 shortens the display time and reduces the brightness by half
ge=OFF; //Close the ones digit selection
LEDBus=LEDTab[d[1]]; //The ten digit is sent to the digital tube for display
shi=ON; //Open the tens digit selection


delay(2); //1 means display for 1 millisecond, 0 shortens the display time and reduces the brightness by half
shi=OFF; //Disable the tens digit selection


LEDBus=LEDTab[d[2]]; //Hundreds digit is sent to digital tube for display
bai=ON; //Open the hundreds digit selection
db=0; //Display decimal point
delay(2); //1 means display for 1 millisecond, 0 shortens the display time and reduces the brightness by half
bai=OFF; //Disable hundreds digit selection
db=1; //Turn off decimal point display
LEDBus=LEDTab[d[3]]; //Thousands digit is sent to digital tube for display
qian=ON; //Open the thousands digit selection
delay(2); //1 means display for 1 millisecond, 0 shortens the display time and reduces the brightness by half
qian=OFF; //Close the thousands digit selection
}
/****************************************************** *****************
Function name: main function
Call: None
Parameters: None
Return value: None
Result: Infinite loop at the beginning of the program
Remark:
*************************************************** ****************/
void main (void)
{
P1M0 = 0x60; //P1.0/P1.1: 0000 0011 (high impedance) //Note: When changing the ADC channel, the corresponding IO interface must also be changed to high impedance input.
P1M1 = 0x00; //P1.0/P1.1: 0000 0000
while(1){
uchar i;
delay(1);
i++;
if (i==30)
{
transfer();
i=0;
}
xian_shi();
//delay(10);
}
}