PIC16C72/PIC16F72 based DC voltmeter

PIC16C72/PIC16F72 based DC voltmeter

// Program : Calculates the input voltage of ADC and display the result in a

// 4-digit multiplexed 7-segment display

// Device : PIC16C72/PIC16F72

// Clock : 4MHz

#define digit1 PORTB.F0

#define digit2 PORTB.F1

#define digit3 PORTB.F2

#define digit4 PORTB.F3

#define decimal PORTC.F7

void delay() { // Function for 5mS delay

delay_ms(5);

}

unsigned char display(unsigned char no) { // Function for returning mask values

unsigned char pattern;

unsigned char segment[] = {0x3F, 0x06, 0x5B, 0x4F, 0x66,

0x6D, 0x7D, 0x07, 0x7F, 0x6F};

pattern = segment[no]; // Patterns to be returned

return (pattern);

}

/* Main program starts here */

void main() { unsigned char units, tens, hundreds, thousands;

unsigned long adc_val;

TRISA = 0xFF; // PORTA as input

TRISB = 0x00; // PORTB as output

TRISC = 0x00; // PORTC as output

ADCON0 = 0x41; // Configuring ADC

ADCON1 = 0x00;

Start: // Endless loop

delay();

ADCON0.F2 = 1; // Start conversion

Wait: // Loops until conversion stops

delay();

if (ADCON0.F2 == 1) goto wait; // Checks conversion status

adc_val = ADRES; // Reads ADC register

adc_val = (adc_val*5000)>>8; // Converts adc value to volts

adc_val = adc_val/10; // Omits LSD

/* Converts adc_val to four individual digits */

thousands = adc_val / 1000; // digit_thousands

adc_val = adc_val % 1000;

hundreds = adc_val / 100; // digit_hundreds

adc_val = adc_val % 100;

tens = adc_val / 10; // digit_tens

units = adc_val % 10; // digit_units

/* Formats the digits to desired configuration */

if (units > 5) {

tens = tens + 1; // Add carry to ten's place

units = 0; // Clear Unit's place

}

if (tens > 9) {

hundreds = hundreds + 1; // Add carry to hundred's place

tens = 0; // Clear tens's place

}

if (hundreds > 9) {

thousands = thousands + 1; // Add carry to thousand's place

hundreds = 0; // Clear hundred's place

}

/* Loads mask values to digits */

PORTC = display(thousands); // Send to PORTC

digit1 = 0; // Enable digit 1

delay(); // Add delay

digit1 = 1; // Disable digit 1

PORTC = display(hundreds); // Send to PORTC

digit2 = 0; // Enable digit 2

decimal = 1; // Enable decimal point

delay(); // Add delay

digit2 = 1; // Disable digit 2

decimal = 0; // Disable decimal point

PORTC = display(tens); // Send to PORTC

digit3 = 0; // Enable digit 3

delay(); // Add delay

digit3 = 1; // Disable digit 3

PORTC = display(units); // Send to PORTC

digit4 = 0; // Enable digit 4

delay(); // Add delay

digit4 = 1; // Disable digit 4

goto Start // Repeat forever

}