/*
 Copyright 2021, tslil clingman

 This program is free software: you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
 Foundation, either version 3 of the License.

 This program is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 PARTICULAR PURPOSE. See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 this program. If not, see <https://www.gnu.org/licenses/>.
*/

#include <stdint.h>
#include <avr/pgmspace.h>
#include <util/delay.h>

#include "TinyI2CMaster.h"

#include "font.h"

#define DISP1_ADDR 0x3C
#define DISP2_ADDR 0x3D
#define RTC_ADDR 0x68

// -----------------------------------------------------------------------------
// SSD1306 driver

#define INIT_LEN 7
PROGMEM const uint8_t init[INIT_LEN] = {0xAE, // display off
                                        0x8D, // charge pump
                                        0x14,
                                        0xAF, // display on
                                        0x20,
                                        0xA6, // Normal display
                                        0x02 // page address mode
};

void disp_init(const uint8_t addr, const uint8_t upside_down) {
  i2c_start(addr,0);
  i2c_write(0x00);
  for (uint8_t k = 0; k<INIT_LEN; k++)
    i2c_write(pgm_read_byte(&init[k]));
  if (upside_down) {
    i2c_write(0xA1);
    i2c_write(0xC8);
  }
  i2c_stop();
}

void disp_draw_digit(const uint8_t addr, const uint8_t d, const uint8_t off) {
  for (uint8_t y=0; y<8; y++, i2c_stop()) {
    // Set cursor
    i2c_start(addr,0);
    i2c_write(0x00);
    // Page select
    i2c_write(0xB0|y); // 0<y<8 anyway
    // Column select specialised to halves of screen
    i2c_write(0); // 0..15, lower bits
    i2c_write(0x10|off); // 0x10 .. 0x14, upper bits
    // Prepare to draw
    i2c_start(addr,0);
    i2c_write(0x40);
    for (uint8_t x=0; x<4; x++) {
      // Read the byte
      uint8_t b = pgm_read_byte(&font[d*32+(y*4+x)]);
      // Unpack and draw it
      for (uint8_t j=0; j<4; j++, b>>=2)
        for (uint8_t l=0; l<4; l++)
          i2c_write(((b&1)?0xF0:0x00)|
                    ((b&2)?0x0F:0x00));
    }
  }
}

// -----------------------------------------------------------------------------
// Interface

uint8_t bcd_to_dec(uint8_t k) { return (((k)/16)*10) + ((k)%16); }

uint8_t dec_to_bcd(uint8_t k) { return (((k)/10)*16) + ((k)%10); }

int main(void) {
  // Init screens
  i2c_init();
  disp_init(DISP1_ADDR,1);
  disp_init(DISP2_ADDR,0);
  // Setup input pullups
  DDRA = ~(_BV(DDA0) | _BV(DDA1));
  PORTA = _BV(DDA0) | _BV(DDA1);
  // Tracking state
  uint8_t input = 0, hours = 99, minutes = 99;
  while(1) {
    // Increase hours?
    if (!(PINA&_BV(DDA0))) {
        if ((hours+=1)>23) hours=0;
        input = 1;
    }
    // Increase minutes?
    if (!(PINA&_BV(DDA1))) {
      if ((minutes+=1)>59) minutes=0;
      input = 1;
    }
    // Store changes
    if (input) {
      input = 0;
      i2c_start(RTC_ADDR,0);
      i2c_write(0);
      i2c_write(0); // Seconds
      i2c_write(dec_to_bcd(minutes));
      i2c_write(dec_to_bcd(hours));
      i2c_stop();
    }
    // Draw minutes
    disp_draw_digit(DISP1_ADDR, (minutes/10)%10, 0);
    disp_draw_digit(DISP1_ADDR, (minutes%10), 4);
    // Draw hours
    disp_draw_digit(DISP2_ADDR, (hours/10)%10, 0);
    disp_draw_digit(DISP2_ADDR, (hours%10), 4);
    // Poll for update
    i2c_start(RTC_ADDR,0);
    i2c_write(1);
    i2c_start(RTC_ADDR,2);
    minutes = bcd_to_dec(i2c_read());
    hours = bcd_to_dec(i2c_read());
    i2c_stop();
    // Delay
    _delay_ms(100);
  }
  return 0;
}