/**
 * Midea AC IR driver
 * driving a IR LED at 38 KHz on digital pin 5
 */

#define PIN_AC_IR 5;

unsigned long t0, t;

void setup() {
    Serial.begin(19200);
    Serial.print("Emit IR Remote, pin ");
    Serial.println(PIN_AC_IR);
    pinMode(PIN_AC_IR, OUTPUT);
}

/********************************************************************
 *								    *
 * Driver for Midea AC through IR control			    *
 *								    *
 ********************************************************************/

/* protocol encodes temperatures on 4 bits in a crazy way, range is very limited too */
int midea_temperature(int temp) {
    if ((temp < 17) || (temp > 30))
        return(-1);
    switch (temp) {
        case 17: return(0);
        case 18: return(1);
        case 19: return(3);
        case 20: return(2);
        case 21: return(6);
        case 22: return(7);
        case 23: return(5);
        case 24: return(4);
        case 25: return(12);
        case 26: return(13);
        case 27: return(9);
        case 28: return(8);
        case 29: return(10);
        case 30: return(11);
    }
    return(-1);
}

void send_mark(int us) {
    unsigned long e, t = micros();
    e = t + us;
    while (t < e) {
        digitalWrite(PIN_AC_IR, HIGH);
	if (t - e < 4) {
	    while ((t = micros()) < e);
            digitalWrite(PIN_AC_IR, LOW);
	    break;
	}
	if (t - e < 22) {
	    delayMicroseconds(t-e);
            digitalWrite(PIN_AC_IR, LOW);
	    break;
	}
	delayMicroseconds(22);
	digitalWrite(PIN_AC_IR, LOW);
	t = micros();
	if (t - e < 4) {
	    while ((t = micros()) < e);
	    break;
	}
	delayMicroseconds(4);
	t = micros();
    }
}

void send_space(int us) {
    digitalWrite(PIN_AC_IR, LOW);
    delayMicroseconds(us);
}

void emit_midea_start(void) {
    send_mark(4200);
    send_space(4500);
}

void emit_midea_end(void) {
    send_mark(550);
    send_space(4500);
}

void emit_midea_byte(byte b) {
     int i;
     byte cur = b;
     byte mask = 0x80;

     for (i = 0;i < 8;i++) {
         send_mark(350);
         if (cur & mask)
             send_space(1700);
         else
             send_space(600);
         mask >>= 1;
     }
     cur = ~b;
     mask = 0x80;
     for (i = 0;i < 8;i++) {
         send_mark(350);
         if (cur & mask)
             send_space(1700);
         else
             send_space(600);
         mask >>= 1;
     }
}

void command_midea_ac(byte b1, byte b2) {
    emit_midea_start();
    emit_midea_byte(0xB2);
    emit_midea_byte(b1);
    emit_midea_byte(b2);
    emit_midea_end();
    /* do we need any delay there before reemission ? */
    emit_midea_start();
    emit_midea_byte(0xB2);
    emit_midea_byte(b1);
    emit_midea_byte(b2);
    emit_midea_end();
}

int stop_midea_ac() {
    command_midea_ac(0x7B, 0xE0);
    return(0);
}

int cool_midea_ac(int temp) {
    byte fan_speed = 0x9; /* 1001: 1, 0101: 2, 0011: 3, 1011 : auto, 1110: off */
    byte command = 0x0;   /* 0000: cool, 1100: heat, 1000: auto, 1101: humidity extraction */
    int t = midea_temperature(temp);

    if (t < 0) {
        Serial.print("Failed to convert temperature");
        Serial.println(temp);
        return(-1);
    }
    command_midea_ac(fan_speed << 4 | 0xF, ((byte) t) << 4 | command);
    return(0);
}

int warm_midea_ac(int temp) {
    byte fan_speed = 0x9; /* 1001: 1, 0101: 2, 0011: 3, 1011 : auto, 1110: off */
    byte command = 0xC;   /* 0000: cool, 1100: heat, 1000: auto, 1101: humidity extraction */
    int t = midea_temperature(temp);

    if (t < 0) {
        Serial.print("Failed to convert temperature");
        Serial.println(temp);
        return(-1);
    }
    command_midea_ac(fan_speed << 4 | 0xF, ((byte) t) << 4 | command);
    return(0);
}

void loop() {
     int i;

     t0 = micros();
     cool_midea_ac(23);
     t = micros();
     Serial.print("took :");
     Serial.println(t - t0);

     delay(15000);
     t0 = micros();
     warm_midea_ac(26);
     t = micros();
     Serial.print("took :");
     Serial.println(t - t0);

     delay(15000);
     t0 = micros();
     stop_midea_ac();
     t = micros();
     Serial.print("took :");
     Serial.println(t - t0);


     delay(30000);
}