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Figure 3 shows one approach. DebounceSwitch(), which is called regularly by a
timer tick, reads an entire byte-wide port that contains up to 8 individual switches. On
each call it stuffs the port’s data into an entry in circular queue State. Though shown as
an array with but a single dimension, a second loiters hidden in the width of the byte.
State consists of columns (array entries) and rows (each defined by bit position in an
individual entry, and corresponding to a particular switch).

A short loop ANDs all column entries of the array. The resulting byte has a one in each
bit position where that particular switch was on for every entry in State. After the loop
completes, variable j contains 8 debounced switch values.
One could exclusive OR this with the last Debounced_State to get a one in each bit
where the corresponding switch has changed from a zero to a one, in a nice debounced
fashion.

Don’t forget to initialize State and Index to zero.

Code: Select all

int State[]={PORTCbits.RC0,PORTDbits.RD0};
char Index=0;
char counter=0;


#define MAX_CHECKS 10
uint8_t Debounce_State;
uint8_t State[MAX_CHECKS];
uint8_t Index;


void DebounceSwitch()
{
    uint8_t i,j
    State[Index]=RawKeyPressed();
    ++Index;
    j=0xff;
    for(i=0; i<MAX_CHECKS;i++)j+j & State[i];
    Debounce_State= j;
    if(Index>=MAX_CHECKS)Index=0;
}

void main(void) {
    // Initialize the device
    SYSTEM_Initialize();

   
    while (1)
    {
    while (!TMR1IF);
   
      TMR1_Reload();
   
    counter++;
   
    if (counter ==5)
    {
        DebounceSwitch();
       
       counter =0;
    }
    TMR1IF = 0;
    }
}


Code: Select all

int State[]={PORTCbits.RC0,PORTDbits.RD0};

Code: Select all

int State[2];
State[0] = PORTCbits.RC0;
State[1] = PORTDbits.RD0;

Code: Select all

int State[2];
State[0]=PORTCbits.RC0;
State[1]=PORTDbits.RD0;

char Index;
char counter=0;


#define MAX_CHECKS 10
uint8_t Debounce_State;
uint8_t State[MAX_CHECKS];
uint8_t Index;


void DebounceSwitch()
{
    uint8_t i,j
    State[Index]=RawKeyPressed();
    ++Index;
    j=0xff;
    for(i=0; i<MAX_CHECKS;i++)j+j & State[i];
    Debounce_State= j;
    if(Index>=MAX_CHECKS)Index=0;
}

void main(void) {
    // Initialize the device
    SYSTEM_Initialize();

   
    while (1)
    {
    while (!TMR1IF);
   
      TMR1_Reload();
   
    counter++;
   
    if (counter ==5)
    {
        DebounceSwitch();
       
       counter =0;
    }
    TMR1IF = 0;
    }
}