// ***********************************************************
// Project:  Loadcell to RS232 Interface via HX711,
//           Micrometer via Heidenhain TTL to RS232
// Author: Dr. Simon Schroedle
// Started: 12/2017
// Module description: Standalone to run on ATMEGA329P
//  data are transmitted as HEX values
//  D: linear encoder data
//  S: Error count linear encoder (invalid code transitions)
//  W: load cell data
//  T: time stamp
// ***********************************************************

// configuration
#define F_CPU				16000000UL

#define HX711_CLOCK_PIN		C,0
#define HX711_DATA_PIN		C,1

#define LENC_A0_PIN C,2 //note: bits hardcoded in ISR
#define LENC_A1_PIN C,3

#define TESTPIN B,0 //for timing measurements

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/delay.h>

#define BAUD    19200UL

#define UBRR_BAUD   ((F_CPU/(16UL*BAUD))-1)

#define UBRR_VAL ((F_CPU+BAUD*8)/(BAUD*16)-1)
#define BAUD_REAL (F_CPU/(16*(UBRR_VAL+1)))

/// Set the specified pin high.
#define AVRPIN_SET(x)			__AVRPIN_SET(x)
#define __AVRPIN_SET(p,b)		PORT##p |= 1<<b
/// Clear the specified pin, set it low.
#define AVRPIN_CLR(x)			__AVRPIN_CLR(x)
#define __AVRPIN_CLR(p,b)		PORT##p &= ~(1<<b)
/// Set the specified pin to the given value.
#define AVRPIN_SET_VALUE(x,v)	if(v) __AVRPIN_SET(x); else __AVRPIN_CLR(x)
/// Configure the specified pin to output.
#define AVRPIN_MKOUT(x)			__AVRPIN_MKOUT(x)
#define __AVRPIN_MKOUT(p,b)		DDR##p |= 1<<b
/// Configure the specified pin to output.
#define AVRPIN_MKIN(x)			__AVRPIN_MKIN(x)
#define __AVRPIN_MKIN(p,b)		DDR##p &= ~(1<<b)
/// Read the current input pin value (PIN).
#define AVRPIN_PIN(x)			__AVRPIN_PIN(x)
#define __AVRPIN_PIN(p,b)		(PIN##p & (1<<b))

/// The DDR register of the specified pin.
#define AVRPORT_DDR(p)			__AVRPORT_DDR(p)
#define __AVRPORT_DDR(p)		(DDR##p)
/// The PIN register of the specified pin.
#define AVRPORT_PIN(p)			__AVRPORT_PIN(p)
#define __AVRPORT_PIN(p)		(PIN##p)
/// The PIN register of the specified pin.
#define AVRPORT_PIN2(x)			__AVRPORT_PIN2(x)
#define __AVRPORT_PIN2(p,b)		(PIN##p)
/// The PORT register of the specified pin.
#define AVRPORT_PORT(p)			__AVRPORT_PORT(p)
#define __AVRPORT_PORT(p)		(PORT##p)

uint8_t ihex[]={0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66};

void uart_init(void)
{
//set baud rate
   UBRR0H = (uint8_t) (UBRR_BAUD>>8);
   UBRR0L = (uint8_t) (UBRR_BAUD & 0x0ff);

   UCSR0B = (1<<TXEN0);

    // 8 data 1 stop bit
   UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01);
}

void usend(uint8_t data)
{
        while ( !( UCSR0A & (1<<UDRE0)) )
            ;
        UDR0 = data;
}

void usend_u8(uint8_t value)
{
   usend (ihex[(value>>4)&0x0fL]);
   usend (ihex[(value)&0x0fL]);
}

static uint8_t hx711_last_timeh;  //timer1 high register
static uint8_t hx711_last_timel;  // ... low register

int hx711_read_32( int32_t* pvalue )
{
	int32_t value = 0;
	uint8_t i;

	if( AVRPIN_PIN( HX711_DATA_PIN ) )
	{
		return 0;
	}

   hx711_last_timel = TCNT1L;  //store timestamp
   hx711_last_timeh = TCNT1H;

	// clock out the bits
	for( i=0; i<24; i++ )
	{
		AVRPIN_SET( HX711_CLOCK_PIN );
		asm("nop");
		asm("nop");
		AVRPIN_CLR( HX711_CLOCK_PIN );
		value <<= 1;
		if( AVRPIN_PIN( HX711_DATA_PIN ) )
		{
			value |= 1;
		}
     asm("nop");
     asm("nop");
	}

	// select the channel and the gain for the next conversion
	AVRPIN_SET( HX711_CLOCK_PIN );
	asm("nop");
	asm("nop");
	AVRPIN_CLR( HX711_CLOCK_PIN );
    asm("nop");
    asm("nop");
	*pvalue = value;
	return 1;
}


signed char graytab[]={0,1,-1,0x10,
                          -1,0,0x10,1,
                          1,0x10,0,-1,
                          0x10,-1,1,0};
/*0x10: error, more than one bit changed */


volatile uint8_t qinp;
volatile uint8_t merror;
volatile int16_t lenc_pos;

ISR (TIMER0_COMPA_vect)  // timer0 overflow interrupt
{
   signed char delta;

//  AVRPIN_SET(TESTPIN);

    qinp>>=2; /* new state in bit 3,2; old state in bit 1,0 */
    qinp|=(AVRPORT_PIN2(LENC_A0_PIN)&0x0c); /* new state in bit 3,2 */

    delta=graytab[qinp];

    if (delta==0x10)
    { delta=0;
       merror++;  }

     lenc_pos+=delta;


 //  AVRPIN_CLR(TESTPIN);


}

int main(void)
{

   int32_t value;
   int16_t enc_value;

   uart_init();
   usend ('%'); //to say hello to the host
   usend ('%');

   AVRPIN_MKIN( LENC_A0_PIN);
   AVRPIN_MKIN( LENC_A1_PIN);

   // hx711_init
	AVRPIN_SET_VALUE( HX711_CLOCK_PIN, 0 );
	AVRPIN_MKOUT( HX711_CLOCK_PIN );
	AVRPIN_MKIN( HX711_DATA_PIN );


   AVRPIN_MKOUT(TESTPIN);

    // CTC mode timer
    TCCR0A |= (1 << WGM01);

    // timer limit for INT
    OCR0A = 128; //125 khz

    TIMSK0 |= (1 << OCIE0A);    //COMPA vect

    TCCR0B |= (1 << CS00);
    // no prescale

    TCCR1B |= (1 << CS12) | (1 << CS10);
    // set prescaler to 1024 and start the timer
    //this is for the timestamp, 0.064 ms resolution

    sei();
    // enable interrupts


    while (1)
    {

        if ( hx711_read_32( &value ) )
                //transmission are triggered by
                //hx711 conversions, about 12 Hz
		{
		    enc_value=lenc_pos;

      //    AVRPIN_SET(TESTPIN);

     	        usend ('D');
                usend (ihex[(enc_value>>12)&0x0fL]);
  	        usend (ihex[(enc_value>>8)&0x0fL]);
		usend (ihex[(enc_value>>4)&0x0fL]);
		usend (ihex[enc_value&0x0fL]);

	        usend ('S');
        	usend (ihex[merror>>4&0x0fL]); //error count
		usend (ihex[merror&0x0fL]); //error count

		usend ('W');
		usend (ihex[(value>>20)&0x0fL]);
		usend (ihex[(value>>16)&0x0fL]);
    		usend (ihex[(value>>12)&0x0fL]);
         	usend (ihex[(value>>8)&0x0fL]);
		usend (ihex[(value>>4)&0x0fL]);
        	usend (ihex[value&0x0fL]);

   	    	usend ('T');
   	    	usend (ihex[(hx711_last_timeh>>4)&0x0f]);
   	    	usend (ihex[hx711_last_timeh&0x0f]);
   	    	usend (ihex[(hx711_last_timel>>4)&0x0f]);
   	    	usend (ihex[hx711_last_timel&0x0f]);

     //     AVRPIN_CLR(TESTPIN);
		}
     }
    return 0;
}