Mini project Digital Volt Meter (DVM) using PIC16F877A with C code

DVM Project Overview

. But PIC can operate only up to +5 V. So to measure the +50 V, the voltage divider is used. This divider divides the input voltage 10 times so that +50V input voltage now becomes +5V at the PIC input.  Inside PIC a program is written which multiplies the converted digital value by 10 before sending it to the LCD display. A screen capture of a rough design of the project in Proteus 7.0 Professional is given below.

1. A/D Result High Register (ADRESH)
2. A/D Register Low Register (ADRESL)
3. A/D Control Register 0 (ADCON0)
4. A/D Control Register 1 (ADCON1)

The structure of ADICON1

LDC Display (16 x 2)

C Source Code

#include <htc.h>
#define data PORTB
#define RS RD0
#define EN RD1
 
__CONFIG(HS & WDTDIS & PWRTEN & BORDIS & LVPDIS);
 
float valch0,valch1;
 
void delay_ms(int n )
{
    TMR1H=0xEC; 
 TMR1L=0x77;
 T1CKPS1=0;
 T1CKPS0=0;
 TMR1CS=0;
 TMR1IF=0;
 TMR1ON=1;
    while(n>0)
    {
  while(!TMR1IF);
  TMR1IF=0;
  TMR1H=0xEC; 
  TMR1L=0x77;
  n--;
 }
}
 
float select_adc(unsigned char chnl){    // init_adc(channel name);
    CHS2=CHS1=0;CHS0=chnl;
    delay_ms(10);
    ADON=1;
    ADGO=1;
    while(ADGO);
    return (((ADRESH*256+ADRESL)*5.0/1023)*10);
}
 
 
 
 
void LCD_Write(unsigned char values,int rs){
 data = values;
 RS = rs;    // rs=0 command and rs=1 data
 EN = 1;
 delay_ms(1);
 EN = 0;
}
 
void LCD_clear(void){
 LCD_Write(0x01,0);  //this clears LCD
}
 
void LCD_goto(unsigned char row,unsigned char column){
 if(row==1){
  LCD_Write(0x80+column,0);
 }
 else if(row==2){
  LCD_Write(0xC0+column,0);
 }
}
 
void LCD_num(int n){
 
  LCD_Write((n/100)+48,1);
  LCD_Write(((n%100)/10)+48,1);
  LCD_Write((n%10)+48,1);
}
 
void initLCD(void){
 
 TRISD=0x00;//as output
 TRISB = 0x00;
 delay_ms(100);
 
 
 LCD_Write(0x30, 0); //8 - bit display
 EN=1; EN = 0;
 LCD_Write(0x38,0);    //2 lines mode
 
 
 
 LCD_Write(0x0C,0);    //dispaly on , cursor blinking
 delay_ms(1);
 
 LCD_clear();LCD_goto(1,0);delay_ms(1);
 LCD_goto(1,7);
 LCD_Write('D',1);delay_ms(100);
 LCD_Write('V',1);delay_ms(100);
 LCD_Write('M',1);delay_ms(100);
 LCD_goto(2,12);
 LCD_Write('v',1);delay_ms(100);
 LCD_goto(2,7);
 LCD_Write('.',1);delay_ms(100);
 
}
 
void main(void){
    PCFG3=PCFG2=PCFG1=PCFG0=0;
 ADFM=1;
 ADCS1=1;
 ADCS0=0;
    TRISA=0xFF;
 initLCD();
 
    while(1){
 
        valch0=select_adc(0);
        valch1=select_adc(1);
 
 
        if(valch0 <= 0.00 && valch1!=0){
            valch0=valch1;
            LCD_goto(2,1);
            LCD_Write('-',1);
            delay_ms(5);
        }
 
        else{
            LCD_goto(2,1);
            LCD_Write('+',1);
            delay_ms(5);
        }
 
 
        LCD_goto(2,4);
        LCD_num(valch0);
        LCD_goto(2,8);
        LCD_num((valch0-(int)valch0)*1000);
 
    }
}