#include <avr/io.h>
#include <avr/sleep.h>

#include "LCDDisplay.h"


#define SHT_IN PINB
#define SHT_PORT PORTB
#define SHT_DDR DDRB
#define SHT_DATA PB6
#define SHT_CLK  PB7

#define SHT_DATA_1  	DDRB &= ~(1 << SHT_DATA) //write "1" to bus (tristate, pullup will pull to high)
#define SHT_DATA_0		DDRB |= (1<< SHT_DATA)    //write "0" to bus (drive bus low)
#define SHT_DATA_IN		(SHT_IN >> PB6)
#define SHT_CLK_1     	DDRB &= ~(1 << SHT_CLK)
#define SHT_CLK_0 		DDRB |= (1<<SHT_CLK)

#define SHT_RESET 0x1e
							//Addr Cmd  R/W
#define MEASURE_TEMP 0x03   //000  0001 1
#define MEASURE_HUMI 0x05   //000  0010 1

#define ACK 1
#define NACK 0

enum {TEMP, HUMI};


typedef union 
{ unsigned int i;
  //float f;
} result;

/*
* return 0 on error
*/
unsigned char sht_write_byte(unsigned char data);

/*
read with ack if ack=1, if ack=0 read with nack.
return read byte
*/
unsigned char sht_read_byte(unsigned char ack);

/*
start transmission
*/
void sht_trans_start(void);

/*
reseth sht connection
*/
void sht_connection_reset(void);

/*
perfomr a softreset of the sht
returns error=1 in case of no response
*/
unsigned char sht_softreset(void);


/*print array*/
void disp_array(unsigned char buf[], char size);

unsigned char sht_measure(unsigned int *result, unsigned char *checksum, unsigned char mode);



void main(void){

	result humi_val,temp_val;
  	unsigned char error,checksum;
  	unsigned int i;

	char buf[16];

	SHT_PORT &= ~(1<<PB6|1<<PB7);
	SHT_DDR  &= ~(1<<PB6|1<<PB7);
	
	disp_init();
	disp_data('O');
	disp_data('k');
  
  sht_connection_reset();
  while(1)
  { 
  	disp_cmd(DISP_RETHOME);
	_delay_ms(50);
    error=0;
    error+=sht_measure( &temp_val.i,&checksum,TEMP);  //measure temperature
    if(error!=0){
	 	sht_connection_reset();                 //in case of an error: connection reset
    	disp_data('E');
		_delay_ms(200);
	}
	else
    { 
	  snprintf(buf, 16, "0x%X 0x%X", temp_val.i, checksum);
	  disp_array(buf, 16);
    }
    _delay_ms(200);
	_delay_ms(200);
	_delay_ms(200);
	_delay_ms(200);
  }


}


unsigned char sht_write_byte(unsigned char data){

	unsigned char i, error=0;
	for(i=0x80; i>0; i=i/2){
		if(i&data) SHT_DATA_1;
		else SHT_DATA_0;
		SHT_CLK_1;
		_delay_us(5);
		SHT_CLK_0;
		_delay_ms(100);
	}
	//release Bus, SHT_DATA=1
	SHT_DATA_1; //direction input
	
	SHT_CLK_1; //release Bus
	error=SHT_DATA_IN; //Get ack or nack
    SHT_CLK_0;

	return error; //error=1 on nack
}

void sht_trans_start(void){

	SHT_CLK_0;
	SHT_DATA_1;
	_delay_us(5);
	SHT_CLK_1;	
	_delay_us(5);
	SHT_DATA_0;
	_delay_us(5);
	SHT_CLK_0;
	_delay_us(5);
	SHT_CLK_1;
	_delay_us(5);
	SHT_DATA_1;
	_delay_us(5);
	SHT_CLK_0;

}

unsigned char sht_read_byte(unsigned char ack){

	unsigned char i, val=0;
	SHT_DATA_1; //release bus (let the sht drive bus)
	for(i=0x80; i>0; i/=2){
		SHT_CLK_1;
		if(SHT_DATA_IN) val =(val|i);
		_delay_ms(10);
		SHT_CLK_0;
		_delay_ms(100);
	}
	if(ack==1) SHT_DATA_0; //pull down if ack==1 (send ack)
	SHT_CLK_1;
	_delay_us(5);
	SHT_CLK_0;
	_delay_us(5);
	SHT_DATA_1;
	return val;	
}


void sht_connection_reset(void){
	unsigned char i;
	SHT_DATA_1;
	SHT_CLK_0;
	for(i=0; i<9; i++){
		SHT_CLK_1;
		SHT_CLK_0;
	}
	
	sht_trans_start();
}	

unsigned char sht_softreset(void){
	unsigned char error=0;
	sht_connection_reset();
	error+=sht_write_byte(SHT_RESET);
	_delay_ms(15); //wait at least 11 ms after this command
	return error; 
}

unsigned char sht_measure(unsigned int *result, unsigned char *checksum, unsigned char mode){
	unsigned char error=0;
	unsigned int i;
	sht_trans_start();
	switch(mode){
		case TEMP: error+=sht_write_byte(MEASURE_TEMP); break;
		case HUMI: error+=sht_write_byte(MEASURE_HUMI); break;
		default: break;
	}
	while(!SHT_DATA_IN){
		 asm volatile ("nop");
	}

	*result=(sht_read_byte(ACK) << 8);	
	*result=*result + sht_read_byte(ACK); 

	*checksum=sht_read_byte(NACK);
	return error;
}



void disp_array(unsigned char buf[], char size){
	
	while(*buf!='\0' && size--){
		if(size==7){
			disp_cmd(DISP_L2);
		}
		disp_data(*buf);
		buf++;
	}

}