AVR Freaks

Dear All,

Thanks for your keen interest about my problem.

I am providing the specific code where i am facing problem herewith.

///  THIS FUNCTION WORKS FINE

unsigned char EXTROM_read_B(unsigned int Rom_Add )//unsigned int Rom_Add
{
PORTD = PORTD |((0<<1)|(0<<2)|(0<<3));
unsigned char *p = (unsigned char *)(OFFSET+Rom_Add);
RomData_B=*p;
return *p;//RomData;
}

/////  THIS FUNCTION DISTURBING ABOVE PROGRAM  ////

unsigned char EXTROM_read_K(unsigned int Rom_Add )//unsigned int Rom_Add
{
unsigned char *p = (unsigned char *)(OFFSET+Rom_Add);
RomData_K=*p;
return *p;//RomData;
}
//-------------------------------------------------------------------------------------------

void KB_Scan()

    {
    PORTD = (PORTD |(1<<1)|(0<<2)|(0<<3));//
kk:    EXTROM_read_K(0XAAAA);
    if (RomData_K != 0xFF)
        {
        goto kk;//ANY ACTION TO PERFORM
        }    
    }
    

Dear joeymorin i have no pin in my 162, 

strictly saying i am having PD1,PD2,PD3, RD/, WR/ pins to read KB status in my design.

If you watching the External Data ROM circuit you found , i have considered 27c010, & i have used PD0 for A16 of External rom. Another 2 pin for DAC, & another 2 pins for I2C application.

Dear Someguy22

it's ROM not RAM , i used it for External Data Keeping

Dear All now i have changed my CKT through port C instead of PORT A , now i am facing another problem--

If i activate col-1 through port D1 & what ever data i am getting through port C is replicating when ever i am activating PORT D2 & PORT D3.

Please give your suggestion.

Dear Kartman ,

are you suggesting me to add diode against my post given on 31/12/2015 or in generalised you are suggesting?

I have still not used any diode for my given circuit.

Ok guys i am once again attaching my latest schematics with this code modified---

Here i am releasing port C for normal port operation & selecting 3 rows through Demultiplexer 74ls138.

it is working with only 1 row what ever row i am selecting first among 3 rows, after releasing full port C. Here is the code along with schematics---

                    DDRC = 0x00; //port C I/P
                    SFIOR = (1<<XMM2) |(1<<XMM1) | (1<<XMM0); // Release Full Port C.
                    
                    PORTD = PORTD |((1<<1)|(0<<2)|(0<<3)); //Select Row-1
                    asm("nop");
                    if (PINC != 0xFF)// check until all key release row-1
                    {
                    KB_Scan();//goto rr;
                    }
                    while (PINC != 0xFF);
                   
                   
                    PORTD = PORTD |((0<<1)|(1<<2)|(0<<3)); //Select Row-2
                    asm("nop");
                    if (PINC != 0xFF)// check until all key release row-2
                    {
                    KB_Scan();//goto rr1;
                    }
                    while (PINC != 0xFF);
                    PINC = 0xFF;
                   
                    PORTD = PORTD |((0<<1)|(0<<2)|(1<<3)); //Select Row-3
                    asm("nop");
                    if (PINC != 0xFF)// check until all key release row-3
                    {
                    KB_Scan();//goto rr2;
                    }
                    while (PINC != 0xFF);
                    PINC = 0xFF;        
                    PORTD = (PORTD |(0<<1)|(0<<2)|(0<<3)); //no Select
                    SFIOR = (0<<XMM2) |(0<<XMM1) | (0<<XMM0); // 
                    

Dear TPE ,

thanks for your comments,

in reality i have used 3 PNP transistor for row select through collector line,

Code is working , but only first row detecting.

Hi every one thanks everyone for your valuable suggestion.

Once again i am attaching the code & actual drawing for the key board ckt.

Row-1: PORTD = PORTD |(1<<1)|(0<<2)|(0<<3); //Select Row-1

        asm("nop");
        asm("nop");
        if (PINC != 0xFF)
        {
        goto xx1;
        }
        PORTD = PORTD |(0<<1)|(0<<2)|(0<<3);// Blank out
        asm("nop");
        asm("nop");
        

 Row-2:PORTD = PORTD |(0<<1)|(1<<2)|(0<<3); //Select Row-2
        asm("nop");
        asm("nop");
        if (PINC != 0xFF)
        {
        goto xx2;
        }
        PORTD = PORTD |(0<<1)|(0<<2)|(0<<3);// Blank out
        asm("nop");
        asm("nop");
    

 Row-3:PORTD = PORTD |(0<<1)|(0<<2)|(1<<3); //Select Row-3
        asm("nop");
        asm("nop");
        
        if (PINC != 0xFF)
         {
        goto xx3;
        }
        PORTD = PORTD |(0<<1)|(0<<2)|(0<<3);// Blank out
        asm("nop");
        asm("nop");
        
        goto xxreturn;// if not pressed then out
    

Main problem iam facing that :

If i am pressing any key of ROW-1 by selecting  PORTD = PORTD |(0<<1)|(0<<2)|(0<<3) i am able to read PIN C.all function of ROW-1 working fine.

and if i am pressing other key of ROW-2 or ROW-3 after release of previous switch of ROW-1 i am getting the same result as i got for ROW-1.

I hope the transistor what i am using BC547B is not de-selecting at the time of selecting ROW-2/ROW3.

What i am suspecting is is it not due to propagation delay of transistor BC547B. please give your view.

Thanks Kartman ,

I will test it today & update u accordingly

Once again
in continuation with this topic i would like to inform you all , i have tested successfully Danne code for debounce with this 24 nos. of key switch & its working excellently beyond my expectation.

Thanks to JohanEkdahl & Danne & others too for their excellent result oriented topic.