Digits not displayed properly, Unable to control output at particular pin - c

Question

I am trying to display my input at microcontroller ATmega16 to 7 segment displays.
I have found the following code on http://www.avr-tutorials.com/projects/atmega16-based-digital-clock but when I implimented it, it is not working. I am getting a fluctuating output i.e I am not able to control the output at particular pins.
I have two inputs temp1 and temp2, and I want to display each of them on three 7-segment displays. Also, I have not used Pins 2 & 3 as they are interrupt pins and I have used them somewhere else. Pin0,1,4,5,6,7 are used.
The code works fine when some delay is added, otherwise output is generated at random pins.
i.e. The output which I was suppose to display from PIND1 is displayed on all pins,
My code:
#include <avr/delay.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#define SegDataPort PORTC
#define SegDataPin PINC
#define SegDataDDR DDRC
#define SegCntrlPort PORTD
#define SegCntrlPin PIND
#define SegCntrlDDR DDRD
/*
* Function Description:
* Encode a Decimal Digit 0-9 to its Seven Segment Equivalent.
*
* Function Arguments:
* digit - Decimal Digit to be Encoded
* common - Common Anode (0), Common Cathode(1)
* SegVal - Encoded Seven Segment Value
*
* Connections:
* Encoded SegVal is return in the other G-F-E-D-C-B-A that is A is the least
* significant bit (bit 0) and G bit 6.
*/
unsigned char DigitTo7SegEncoder(int digit, unsigned char common)
{
unsigned char SegVal;
switch(digit)
{
case 0: if(common == 1) SegVal = 0b00111111;
else SegVal = ~0b00111111;
break;
case 1: if(common == 1) SegVal = 0b00000110;
else SegVal = ~0b00000110;
break;
case 2: if(common == 1) SegVal = 0b01011011;
else SegVal = ~0b01011011;
break;
case 3: if(common == 1) SegVal = 0b01001111;
else SegVal = ~0b01001111;
break;
case 4: if(common == 1) SegVal = 0b01100110;
else SegVal = ~0b01100110;
break;
case 5: if(common == 1) SegVal = 0b01101101;
else SegVal = ~0b01101101;
break;
case 6: if(common == 1) SegVal = 0b01111101;
else SegVal = ~0b01111101;
break;
case 7: if(common == 1) SegVal = 0b00000111;
else SegVal = ~0b00000111;
break;
case 8: if(common == 1) SegVal = 0b01111111;
else SegVal = ~0b01111111;
break;
case 9: if(common == 1) SegVal = 0b01101111;
else SegVal = ~0b01101111;
}
return SegVal;
}
int main(void)
{
int temp1,temp2;
//Suppose my input is 105 and 210, i.e. temp1=105 and temp2=210;
// it contains other information also, not required here
SegDataDDR = 0xFF;
SegCntrlDDR = 0xF3;
SegCntrlPort = 0xF3;
SegDataPort = 0x00;
while(1){
SegDataPort = DigitTo7SegEncoder(temp1%10,1);
SegCntrlPort = ~0x01;
SegDataPort = DigitTo7SegEncoder((temp1/10)%10,1);
SegCntrlPort = ~0x02;
SegDataPort = DigitTo7SegEncoder(temp1/100,1);
SegCntrlPort = ~0x10;
SegDataPort = DigitTo7SegEncoder(temp2%10,1);
SegCntrlPort = ~0x20;
SegDataPort = DigitTo7SegEncoder((temp2/10)%10,1);
SegCntrlPort = ~0x40;
SegDataPort = DigitTo7SegEncoder(temp2/100,1);
SegCntrlPort = ~0x80;
}}

Answer 1

You don't set the DDRs to output anywhere. The pins you want to use as outputs must have the corresponding bit in DDRx set to 1. Otherwise it remains an input pin.
An input pin will show an output, but with a lower current and a more slowly rising edge. Drawing on that current with an LCD may cause the voltage to drop.

Answer 2

Provided that these 7-segment components don't contain any sequential logic inside this is what actually happens:
SegDataPort = DigitTo7SegEncoder(temp1%10,1); // You write the data
SegCntrlPort = ~0x01; // You enable the first 7-segment component
// Then without any delay...
SegDataPort = DigitTo7SegEncoder((temp1/10)%10,1); // You write other data
SegCntrlPort = ~0x02; // You enable the second component
// The without any delay...
So actually the 7-segment component displays previous and next digits at once for a short time.
What about this? (just a pseudocode)
SegCntrlPort = 0xFF; // hide everything
SetDataPort = ... value1 ...;
SegCntrlPort = ~0x01; // show it
WaitForAWhile();
SegCntrlPort = 0xFF; // hide everything to avoid unwanted transitions
SetDataPort = ... value2 ...;
SegCntrlPort = ~0x02; // show it
WaitForAWhile();
And so on.