O/P not Extected in CAMMON ANODE 7-SEGMENTS

[sajsaj220]

Could u please let me know what is the issue for not getting expected o/p from 4 digit 7seg in XC8 16F877A uC. The Ckt diag. and Code is here.

I am getting as o/p in 7seg only 0 and 8 but all control and data pins in mcu portion is blinking but all the control pins(1,2,3,4) under 7seg portion not blinking.

#include <xc.h>

//***Define the signal pins of all four displays***//
#define s1 RC0
#define s2 RC1
#define s3 RC2
#define s4 RC3
//***End of definition**////

void main()
{
unsigned int a,b,c,d,e,f,g,h; //just variables
int i = 0; //the 4-digit value that is to be displayed
int flag =0; //for creating delay

unsigned int seg[]={0XC0, //Hex value to display the number 0
                    0XF9, //Hex value to display the number 1
                    0XA4, //Hex value to display the number 2
                    0XB0, //Hex value to display the number 3
                    0X99, //Hex value to display the number 4
                    0X92, //Hex value to display the number 5
                    0X82, //Hex value to display the number 6
                    0XF8, //Hex value to display the number 7
                    0X80, //Hex value to display the number 8
                    0X90  //Hex value to display the number 9
                   }; //End of Array for displaying numbers from 0 to 9// FOR CA
 

//*****I/O Configuration****//
TRISC=0X00;
TRISD=0x00;

PORTC=0XFF; // FOR CA

//***End of I/O configuration**///

#define _XTAL_FREQ 20000000

while(1)
{
    
  //***Splitting "i" into four digits***//  
a=i%10;//4th digit is saved here
b=i/10;
c=b%10;//3rd digit is saved here
d=b/10;
e=d%10; //2nd digit is saved here
f=d/10;
g=f%10; //1st digit is saved here
h=f/10;
//***End of splitting***//

PORTD=seg[g];s1=0; //Turn ON display 1 and print 4th digit
__delay_ms(10);s1=1;     //Turn OFF display 1 after 5ms delay
PORTD=seg[e];s2=0; //Turn ON display 2 and print 3rd digit
__delay_ms(10);s2=1;     //Turn OFF display 2 after 5ms delay
PORTD=seg[c];s3=0; //Turn ON display 3 and print 2nd digit
__delay_ms(10);s3=1;     //Turn OFF display 3 after 5ms delay
PORTD=seg[a];s4=0; //Turn ON display 4 and print 1st digit
__delay_ms(10);s4=1;     //Turn OFF display 4 after 5ms delay

if(flag>=10) //wait till flag reaches 100
{
    i++;flag=0; //only if flag is hundred "i" will be incremented 
}
flag++; //increment flag for each flash
}
}

 

[betwixt]

Obvious problems:

Electrically you overload the PIC RD0 to RD6 pins, you must fit current limiting resistors in each of them.

if(flag>=10) //wait till flag reaches 100
{
    i++;flag=0; //only if flag is hundred "i" will be incremented 
}
flag++; //increment flag for each flash

Can never reach 100 and if you are using it as a delay it will be very short (a few uS). A better method if you want a reliable count speed is to use a timer interrupt.

Brian.

 

[sajsaj220]

tnx for reply.
i have tested with same code and same ckt in proteus except (removing) bc557, ie, directly connecting all 4 control pins between mcu & digit, there was no problebs working correctly.
But If add bc557, as ckt attached getting NOTHING ELSE EXCEPT 0 and 8(ie, 0 0 0 0 and 8 8 8 8).

As per you,
If it is "flag" issue, then why it will work in DIRECT connect control pin?
Could u clera the matter..

 

[FvM]

Proteus is a strange simulator, the multi-digit 7-segment displays are modelled in a special way as pulse extending circuits to get a smooth display. Driving it with an open collector driver may give unexpected results.

 

[sajsaj220]

i think base resistor is the problems. Could u please let me know how do I calculate base resistor for this matter..
thx

 

[sajsaj220]

ALONG WITH #4, what simulator is best??

 

[FvM]

The base resistor is O.K., at least for simulation purposes. In real hardware, a current limiting collector resistor would be necessary.

I guess the simulation problem is that the pin 1-4 signals are not recognized as valid digital level. May be pull-down resistors can change the behaviour.

ALONG WITH #4, what simulator is best??

It depends on the simulation purpose. Proteus is unique as co-simulator of microcontroller code and discrete hardware. But it has some limitations and pitfalls.