Interfacing Seven Segment (c.c) Display
In this tutorial i will show you how to interface S.S display with PIC16F887/877. For this we required 74hc573 latches, 74hc238 decoder, and 74ls48 bcd2dec converter.
Latches are used to enable/disable the S.S, 74hc234 a 3x8 decoder selects the appropriate latch to be enable/disable. 74ls48 just converts the bcd input to respective decimal output to operate S.S properly.
Now lets write a small program that display the digital manual input at S.S, enter by the user; by using 8-way dip switch.
Code:
void main() {
int x,y,i,j;
trisc=0;
portc=0;
trisd=255; //all bits for input
///////////////// comment 4 pic16f877/////////
ansel=0;
anselh=0;
c1on_bit=0;
c2on_bit=0;
////////////////////////////////////////////
while(1){
j=0;
i=3;
x=portd;
int x,y,i,j;
trisc=0;
portc=0;
trisd=255; //all bits for input
///////////////// comment 4 pic16f877/////////
ansel=0;
anselh=0;
c1on_bit=0;
c2on_bit=0;
////////////////////////////////////////////
while(1){
j=0;
i=3;
x=portd;
while(i>0){
y=x%10;
y=y|j;
delay_ms(100);
portc=y;
x=x/10;
i--;
j=j+16;
}
}
}
Now come towards the code; portc is utilized for o/p, and manual i/p is applied at portd, here. As the ports are 8-bit so, maximum i/p would be 255(0-255); we have to display them on three S.S, for this we have to separate the digits of i/p. Modulus '%' do this job; let say the i/p is 255, then first we have to display 5 then 5 and then 2; to do this we use x%10. Where x is an integer that has the manual i/p. Where modulus operator returns the remainder of integer division, so after this we have 5 stored in y (as 255%10 = 5, remainder is 5).
After getting the digit, it should be display on 3rd S.S; so to select this latch just or '|' y with proper integer, which in this case is 0 (as my 3rd S.S as attached to 0 o/p of latch, 2nd is to 1st and so on). So, after doing this we have 5 in 8-bit and latch 0 is selected. Now display it by assigning it to port.
To display 2nd digit first reduce the i/p by dividing it with 10; 255/10 gives 25, as we are storing this value in an integer; so x is equal to 25, now. J is incremented by 16 because we have to select the first latch (see the diagram for more detail).
In the same fashion, to display the first digit; select proper latch, divide and take modulus and display it, that is it. Here i is used to run this process for three times (means to display all the i/p digit on three S.S).
Schematic:
For reset circuitry please refer to first tutorial.
Schematic:
For reset circuitry please refer to first tutorial.
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| connection diagram |
