#include "cse_avr_board.h"

void uart_putn(unsigned int i, unsigned int base);
void keypad_press(unsigned int *after_milliseconds, int *key_row, int *key_column);

int main(void) {
    const int lcd_length = 14;
    uart_puts("Link PB0-PB7 to LCD D0-D7 (8 wires)\n");
    uart_puts("Link PD0-PD3 to LCD BE-RS (4 wires)\n");
    uart_puts("Link PC0-PC3 to Keypad R0..R3 (4 wires)\n");
    uart_puts("Link PA0-PA3 to Keypad C0..C3 (4 wires)\n");
    while (1) {
        lcd_set_line(0,"");
        lcd_set_line(1,"Texting Lab");
        char buffer[lcd_length + 1];
        for (int i = 0; i < sizeof buffer;i++)
            buffer[i] = 0;
        for (int column = 0; column < lcd_length; column++) {
            int milliseconds, key_row, key_column;
            keypad_press(&milliseconds, &key_row, &key_column);
            char c = "123A456B789C*0#D"[key_row*4+key_column];
            uart_puts("After ");
            uart_putn(milliseconds, 10);
            uart_puts("ms you typed a: '");
            uart_putchar(c);
            uart_puts("'\n");
            buffer[0] = c;
            lcd_set_line(0, buffer);
        }
    }
    return 0;
}

//
// wait for keypad key to be pressed and released
// row, column and waiting time before it was pressed are returned
//
void keypad_press(unsigned int *after_milliseconds, int *key_row, int *key_column) {
    volatile unsigned char *portc_control_address = (char *)0x34;
    volatile unsigned char *portc_output_address = (char *)0x35;
    volatile unsigned char *porta_input_address = (char *)0x39;
    volatile unsigned char *porta_control_address = (char *)0x3A;
    volatile unsigned char *porta_output_address = (char *)0x3B;
    
    *portc_control_address = 0x0f;
    *porta_control_address = 0x00;
    int milliseconds = 0;
    while (1) {
        for (int row = 0; row < 4; row++) { 
            *porta_output_address = 0x0f;                // pull PA0..PA3 = keypad C0-C3 high
            *portc_output_address = 0x0f & ~(1 << row);  // pull a row line low
            wait(1,0);                                   // wait 1 millisecond for settling
            int input = *porta_input_address & 0xf;      // input PA0..PA3 = keypad C0-C3 
            milliseconds++;
            int column;
            for (column = 0; column < 4; column++)
                if (!(input & (1 << column)))
                    break;
            if (column != 4) {
                while ((*porta_input_address & 0xf) == input)
                    ;
                *key_row = row;
                *key_column = column;
                *after_milliseconds = milliseconds;
                return;
            }
        }
    }
}

// print to uart number in specified base

void uart_putn(unsigned int i, unsigned int base) {
    if (base > 16)
        base = 16;
    unsigned int j = i / base;
    if (j) {
        uart_putn(j, base);
        i -= j * base;
    }
    uart_putchar("0123456789ABCDEF"[i]);
}