[PIC] pic16f877a scrolling txt help

[Adnan Tariq]

Plz ppl with great knowledge help me. i want to scroll txt but have no idea how to do so.
Following is the code an diagram.



code

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Code dot - [expand]
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#include <pic.h>
 
#define DS RC1
#define SHCP RC0
#define STCP RC2
 
char a[]={0x00,0xF8, 0x14, 0x12, 0x11, 0x11, 0x12, 0x14, 0xF8,
0xFF,0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0xFF,
            0xF8, 0x14, 0x12, 0x11, 0x11, 0x12, 0x14, 0xF8,
};
 
 
 
 
 
 
void delay(unsigned int count)
{
    int i;
    unsigned int x;
    for(x=0;x<count;x++)
        for(i=0;i<525;i++);
}
void main() {
 
unsigned int j,z;
TRISC=0x00;
 
TRISD=0x00;
TRISB=0x00;
while(1)
{
 
              
               
               for (z=0;z<=24;z++)
               { 
                 PORTB=~a[z];
   
                  if(z==0)
                  {
                     DS=1;
                  }
                  else
                  {
                     DS=0;
                  }
                 
                  SHCP=1;
                  SHCP=0;
 delay(0.1);
                  STCP=1;
                  STCP=0;
 
               }

---

 

[ud23]

https://embedded-lab.com/blog/?p=2661

 

[Adnan Tariq]

yes sir i read that but what should i do in coding

sir scrolling part is a bit difficult to understand in the link.

 

[ud23]

sorry for late reply but for scrolling a display you need to shift the column indexing by 1 position.same thing is done in the link logic. string length is the number of characters in the text.

you can try other simple way given in the below link.

https://www.edaboard.com/threads/206350/

 

[Easyrider83]

Sclroll up/down:
You need to shift bits in each byte of your array and don't lost the first/last one. For shift left you should store in temporary variable the MSB bit, then apply shift operation (byte << 1) and then set the LSB bit according the MSB.
Then repeat this for all bytes in array.
Scroll left/right: simply move all bytes in array left or write and don't forget about the first/last one.

void StringMoveLeft (char * String, char Len)
{
        char tmp;
        char dat = String[0];
        char cnt;
        if (Len) tmp = Len-1;
                else tmp = StringLen(String)-1;
        for (cnt=0; cnt!=tmp; cnt++) String[cnt]=String[cnt+1];
        String[tmp]=dat;
}

void StringMoveRight (char * String, char Len)
{
        char tmp;
        char dat;
        char cnt;
        if (Len) tmp = Len-1;
                else tmp = StringLen(String)-1;
        dat = String[Len-1];
        for (cnt=tmp; cnt!=0; cnt--) String[cnt]=String[cnt-1];
        String[0]=dat;
}

PS. Schematic unreadable!!! :bang:
Who teached you to route the wires???

 

[Adnan Tariq]

hehe sorry for the wires ok i am able to shift now i made it simple but now when i implement on hardware i burned my code to pic found rows and columns and placed wires but it wont show anything. is something wrong with my code plz check...

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Code C - [expand]
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unsigned char col_a[]={1,2,4,8,16,32,64,128};
unsigned char row_a[]={0x20,0x50,0x88,0x88,0xf8,0x88,0x88,0x88};
char i,shift=4,first=1;
unsigned int j,count;
void Delay_ms(unsigned int count)
{
    int i;
    unsigned int x;
    for(x=0;x<count;x++)
        for(i=0;i<525;i++);
}
 
void main(void)
{
TRISB=0X00;
TRISC=0X00;
PORTB=0X00;
PORTC=0X00;
 
 
 
for(;;)
 
while(first==1)
{
for(i=0;i<=7;i++)
{
PORTC=~col_a[i]  ;
PORTB=row_a[i] << shift;
Delay_ms(4);
count++;
if(count==25)
{
shift--;
count=0;
if(shift==0)
{
//shift=0;
first=0;
}
}
}
}
 
while(first==0)
{
for(i=0;i<=7;i++)
{
PORTC=~col_a[i]  ;
PORTB=row_a[i] >> shift;
Delay_ms(4);
count++;
if(count==25)
{
shift++;
count=0;
if(shift==9)
{
shift=4;
first=1;
}
}
}
}
 
}
}

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- - - Updated - - -

i used 4mhz crystaline oscillator and burned through micro c did i missed something..

 

[Allen6502]

I didnt see the 2 22pF capacitors near the crystal.

And where is the 10K resistor on the MCLR to Vcc?

Allen

 

[Adnan Tariq]

i was told to place crystalline oscillator directly to the pic giving 5v to mclr ,vdd and grounding vss

 

[Adnan Tariq]

and resistors used for led are around 150 ohms

 

[Allen6502]

Did you connect the 877A as in the picture attached?

Or you have a 3-pin crystal like the one in the pix attached?

Allen

 

[theenggprojects]

The first image is the right one, I have never seen this 3 pin oscillator before

 

[Allen6502]

They are available from eBay here

**broken link removed**

and I have both 4 Mhz and 20 Mhz types. The caps are built inside like the attached pix.

Allen

 

[Adnan Tariq]

i m using two pin oscillator

- - - Updated - - -

allen i have not used capacitors directly attached oscillator. how much voltage should i give to mclr and vdd. didnt used 10k either.

 

[theenggprojects]

two pin oscillator is good here, and give +5v to microcontroller and there's no need to use capacitor with the oscillator, instead use capacitor between +5V and GND.