Hello all:

I am constructing a temperature display which will read in from a thermocouple or some other device on RA0, and display the result on four digits. RA1 - RA4 will be digit select while portb will be a-g and decimal point. I am having trouble getting initial values for each digit onto my seven segment displays, it is not putting out the first digit, which should be a zero. Can anyone help me? Attached is my incomplete code.

#include <system.h>
#pragma CLOCK_FREQ 8000000 //config clock to 8mhz.
#pragma DATA _CONFIG, _INTRC_IO & _WDT_OFF & _CP_OFF & _PWRTE_OFF & _LVP_OFF & _BODEN_OFF & _MCLR_OFF

const char SSEG[] = {
0b11000000, // 0, LED Segment: A,B,C,D,E,F
0b11111001, // 1, LED Segment: B,C
0b10100100, // 2, LED Segment: A,B,D,E,G
0b10110000, // 3, LED Segment: A,B,C,D,G
0b10011001, // 4, LED Segment: B,C,F,G
0b10010010, // 5, LED Segment: A,C,D,F,G
0b10000010, // 6, LED Segment: A,C,D,E,F,G
0b11111000, // 7, LED Segment: A,B,C
0b10000000, // 8, LED Segment: A,B,C,D,E,F,G
0b10010000, // 9, LED Segment: A,B,C,D,F,G
0b11000110, // C, LED Segment: A,D,E,F
0b10001110 // F, LED Segment: A,E,F,G
};

unsigned char DispDigit[4];
unsigned char DigitCount;

void interrupt (void)
{

if(intcon.2 = 1) { // TIMER0 Interrupt Flag


/* Pull Low the Segment */
portb = DispDigit[DigitCount];


/* Activate the Digit and Advanced to next Digit */
porta = ~(1 << DigitCount++);

/* Reset the Digit Count */
if (DigitCount > 3)
DigitCount = 0;
tmr0 = 156; // Initial Value for 3.2 ms Interrupt
intcon.2 = 0; // Clear TIMER0 interrupt flag
}
}

void main(void)
{
unsigned int value;

osccon = 0x70; //setting oscilator to 8MHz
trisa = 0x01; //RA0 as input, all others as output
trisb = 0x00; //configure port B pins as output
adcon0 = 0xC1; //Analog to Digital Converter Register 0 - Int osc, RA0 selected
adcon1 = 0x8E; /*Analog to Digital Converter Register 1 - Right justified, RA0 as input,
all others output*/


/* Init TIMER0: Period: 1/(Fosc/4) x Prescaler x TMR0
0.0005 ms x 64 * 100 = 3.2 ms */
option_reg = 0x05; // 1:64 Prescaler
tmr0 = 156; // Interupt every 3.2 ms
intcon.5 = 1; // Enable interrupt on TMR0 overflow
intcon.7 = 1; // Global interrupt enable
/* Initial variables used */
DigitCount = 0;
DispDigit[0] = SSEG[10]; // Centigrade Sign
DispDigit[1] = SSEG[0]; // Zero Digit
DispDigit[2] = SSEG[0]; // Zero Digit
DispDigit[3] = SSEG[0]; // Zero Digit
while( 1 ) //endless loop
{
adcon0.2 = 1; //Initiate Go/Done bit
while(adcon0.2) continue; // Wait conversion done

value = ADRESL; // Get the 8 bit LSB result
value += (ADRESH << 8); // Get the 2 bit MSB result
}
}

 

I am constructing a temperature display which will read in from a thermocouple or some other device on RA0, and display the result on four digits. RA1 - RA4 will be digit select while portb will be a-g and decimal point. I am having trouble getting initial values for each digit onto my seven segment displays, it is not putting out the first digit, which should be a zero. Can anyone help me? Attached is my incomplete code.

Could you provide a schematic which shows how the displays are connected? Is pin RA4 controlling the first digit that does not work?
My first guess is that this digit is never enabled. I would split this instruction into two lines:

// porta = ~(1 << DigitCount++); 
 
 
DigiCount++;
porta = ~(1 << DigitCount);

In this way, you are sure that DigiCount is incremented first and it can control pins RA1 to RA4 as supposed; not RA0 (that is an input anyways) to RA3.

 

RA1 = hundreds, RA2 = tens, RA3 = ones, RA4 = 1/10

Splitting up that code activated RA4, but RA1 is now off.