KeyPad.h

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#ifndef KEYPAD_H_
#define KEYPAD_H_
 
#include "../Pins/Pins.h"
#include "Core/Keys.h"

inline Keys_t KeyPad_GetKeys()
{
    DDRC = 0xF0;                // taking row pins as output and column pins as input
    PORTC = 0x0F;               // powering the row pins
    
    uint8_t keypressed = 0;     // integer for storing matrix value
    Keys_t keys = KEYNONE;
 
    if (PINC != 0b00001111)     // if any of column pins goes high execute the loop
    {
        keypressed = PINC;      // taking the column value into integer
        PORTC ^= 0b11111111;    // powering column pins of keypad
        DDRC ^= 0b11111111;     // making rows as inputs and columns as outputs
        for(int i=0; i<8; i++) { asm volatile("nop"); } // wait until PORTC has new value
        keypressed |= PINC;     // taking row value and ORing it to column value
        
        // Always returns only one key. Multiple keys not supported with this structure.
        switch(keypressed)
        {
            case 0b11101110: keys = KEY7; break;        // row 1 column 1
            case 0b11101101: keys = KEY8; break;        // row 1 column 2
            case 0b11101011: keys = KEY9; break;        // row 1 column 3
            case 0b11100111: keys = KEYKILO; break;     // row 1 column 4
            case 0b11011110: keys = KEY4; break;        // row 2 column 1
            case 0b11011101: keys = KEY5; break;        // row 2 column 2
            case 0b11011011: keys = KEY6; break;        // row 2 column 3
            case 0b11010111: keys = KEYMILLI; break;    // row 2 column 4
            case 0b10111110: keys = KEY1; break;        // row 3 column 1
            case 0b10111101: keys = KEY2; break;        // row 3 column 2
            case 0b10111011: keys = KEY3; break;        // row 3 column 3
            case 0b10110111: keys = KEYMINUS; break;    // row 3 column 4
            case 0b01111110: keys = KEYLEFT; break;     // row 4 column 1
            case 0b01111101: keys = KEY0; break;        // row 4 column 2
            case 0b01111011: keys = KEYRIGHT; break;    // row 4 column 3
            case 0b01110111: keys = KEYX1; break;   // row 4 column 4
            default: break;
        }
        
        DDRC ^= 0b11111111;     // making rows as outputs and columns as inputs
        PORTC ^= 0b11111111;    // powering row pins of keypad
    }
    return keys;
}
 
#endif /* KEYPAD_H_ */