gps.c

/*
 * gps.c
 *
 * Created: 31-03-2012 15:30:41
 *  Author: Hussain
 */ 

/**
 * @file gps.c
 * @brief Read the GPS data using a UART interrupt
 */

#include "common.h"
#include "peripherals.h"
#include "propagator.h"
#include "gps.h"

///4-byte buffer for the GPS reading
volatile static uint32_t buffer = 0;
///Position variables for the data in GPS structure
volatile static uint8_t pos = 0xFF,vel = 0xFF,dop = 0xFF,geo = 0xFF, time = 0xFF;
///Variables to check whether the message has ended
volatile static uint8_t last_byte, message_end;
//volatile static uint16_t pdop = 0xFFFF;

///Temporary GPS reading
volatile struct GPS_reading gps;

char arrayx[40];

char arrayy[40];

char arrayz[40];


void init_UART_GPS(void)
{

  UCSR0A = 0;
  UCSR0B = 0;
  UCSR0C = 0;
  
  ///Double Baud Rate
  UCSR0A |= _BV(U2X0);
  ///Enable Reception
  UCSR0B |= _BV(RXEN0) | _BV(TXEN0) | _BV(RXCIE0);
  ///8-bit Data Byte, 2 Stop bits
  UCSR0C |= _BV(USBS0) | _BV(UCSZ01) | _BV(UCSZ00);
  ///Set Baud Rate to 9600
  UBRR0L = 103;
  UBRR0H = 0;
}


/** @brief Interrupt on receiving a byte through UART GPS
 */
ISR(USART0_RX_vect)
{ 
  PORTA ^= 0xf0;
  
  ///Buffer the Received Byte
  last_byte = UDR0;
  
  ///Put the received byte in the last 4-bytes buffer
  buffer = buffer << 8;
  buffer &= 0xFFFFFF00;
  buffer |= (uint32_t) last_byte;
  
  ///Check if the last byte was for position
  if(pos < 12)
  {
    
    if(pos<4)
	{
		Current_state.gps.x = Current_state.gps.x >> 8;
		Current_state.gps.x &= 0x00FFFFFF;
        Current_state.gps.x |= ((uint32_t) last_byte)<<24;
        //sprintf(arrayx,"%x %x",last_byte);transmit_string_UART0(arrayx);
		
		//transmit_UART0('\r');*/
	}
	else if (pos<8)
	{
		Current_state.gps.y = Current_state.gps.y >> 8;
		Current_state.gps.y &= 0x00FFFFFF;
		Current_state.gps.y |= ((uint32_t) last_byte)<<24;
		//sprintf(arrayy,"%x %x",last_byte);transmit_string_UART0(arrayy);
		
		//transmit_UART0('\r');*/
	}
	
	else if(pos<12)
	{
		Current_state.gps.z = Current_state.gps.z >> 8;
		Current_state.gps.z &= 0x00FFFFFF;
		Current_state.gps.z |= ((uint32_t) last_byte)<<24;
		//sprintf(arrayz,"%x %x",last_byte);transmit_string_UART0(arrayz);
		
		//transmit_UART0('\r');*/
	}
    ///* Increment position and terminate it if full
    pos++;
    if(pos == 12)
	{
      pos = 0xFF;
	  //Current_state.gps.x = convert_uint32_to_int32((int32_t)Current_state.gps.x1);
	  //Current_state.gps.y = convert_uint32_to_int32(Current_state.gps.y1);
	  //Current_state.gps.z = convert_uint32_to_int32(Current_state.gps.z1);
	   }
	   
  }
  
  ///Check if the last byte was for velocity
  if(vel < 12)
  {
	  
    if(vel < 4)
	{
		Current_state.gps.v_x = Current_state.gps.v_x >> 8;
		Current_state.gps.v_x &= 0x00FFFFFF;
        Current_state.gps.v_x |= ((uint32_t) last_byte)<<24;
		
	}
	else if(vel < 8)
	{
		
		Current_state.gps.v_y = Current_state.gps.v_y >> 8;
		Current_state.gps.v_y &= 0x00FFFFFF;
        Current_state.gps.v_y |= ((uint32_t) last_byte)<<24;
	}
	else if(vel < 12)
	{
		Current_state.gps.v_z = Current_state.gps.v_z >> 8;
		Current_state.gps.v_z &= 0x00FFFFFF;
        Current_state.gps.v_z |= ((uint32_t) last_byte)<<24;
	}
	//*((uint8_t *)&gps.v_x + vel) = last_byte;
	vel++;
    if(vel == 12)
     {
		  vel = 0xFF;
		  //Current_state.gps.v_x = convert_uint32_to_int32(Current_state.gps.v_x1);
		  //Current_state.gps.v_y = convert_uint32_to_int32(Current_state.gps.v_y1);
		  //Current_state.gps.v_z = convert_uint32_to_int32(Current_state.gps.v_z1);

	 }
  }
  
  ///Check if the last byte was for PDOP
  if(dop < 4)
  {
    if(dop >= 2)
    {
		 Current_state.gps.pdop =  Current_state.gps.pdop >> 8;
		 Current_state.gps.pdop &= 0x00FF;
         Current_state.gps.pdop |= ((uint16_t) last_byte)<<8;
     }
//	*((uint8_t *)&pdop + (dop - 2)) = last_byte;
	dop++;
    if(dop == 4)
      dop = 0xFF;
  }
  
  ///Check if the last byte was for Geodetic position
  if(geo < 16)
  {
	if(geo < 4);  
    else if(geo < 8)
	{
		Current_state.gps.lat = Current_state.gps.lat >> 8;
		Current_state.gps.lat &= 0x00FFFFFF;
		Current_state.gps.lat |= ((uint32_t) last_byte)<<24;
	}
	else if(geo < 12)
	{
		Current_state.gps.lon = Current_state.gps.lon >> 8;
		Current_state.gps.lon &= 0x00FFFFFF;
		Current_state.gps.lon |= ((uint32_t) last_byte)<<24;
	}
	else if(geo < 16 )
	{
		Current_state.gps.alt = Current_state.gps.alt >> 8;
		Current_state.gps.alt &= 0x00FFFFFF;
		Current_state.gps.alt |= ((uint32_t) last_byte)<<24;
	}
	
//    *((uint8_t *)&gps.lat + (geo - 4)) = last_byte;
    
    geo++;
    if(geo == 16)
	{
      geo = 0xFF;
	  //Current_state.gps.lat = convert_uint32_to_int32(Current_state.gps.lat1);
	  //Current_state.gps.lon = convert_uint32_to_int32(Current_state.gps.lon1);
	  //Current_state.gps.alt = convert_uint32_to_int32(Current_state.gps.alt1);

	}
  }
  
  ///Check if the last byte was for Time
  if(time < 7)
  {
	  
	  if(time == 0)
	  {
		  Current_state.gps.hours = last_byte;
	  }
	  else if(time == 1)
	  {
		  Current_state.gps.minutes = last_byte;
	  }
	  else if(time == 2)
	  {
		  Current_state.gps.seconds = last_byte;
	  }
	  else if(time == 3)
	  {
		  Current_state.gps.date = last_byte;
	  }else if(time == 4)
	  {
		  Current_state.gps.month = last_byte;
	  }else if(time > 4)
	  {
		  Current_state.gps.year = Current_state.gps.year >> 8;
		  Current_state.gps.year &= 0x00FF;
		  Current_state.gps.year |= ((uint16_t) last_byte)<<8;

	  }
    //*((uint8_t *)&gps.hours + time) = last_byte;
    
    time++;
    if(time == 7)
    {
      time = 0xFF;
      ///* * The Entire message has been read
      message_end = 1;
	 //  UCSR0B &= ~(_BV(RXCIE0)); //remember this change iterrupt off
    }
  }
  
  ///Check the buffer against message ID's
  ///Position
  if(buffer == 0x3F3F04AC)
  {
    message_end = 0;
    pos = 0;
  }
  ///Velocity
  else if(buffer == 0x3F3F05AC)
    vel = 0;
  ///DOP
  else if(buffer == 0x3F3F0BAC)
    dop = 0;
  ///Geodetic System
  else if(buffer == 0x3F3F0EAC)
    geo = 0;
  ///Time
  else if(buffer == 0x3F3F0FAC)
    time = 0;
  
  ///Check if PDOP < 500(factor 100), shut off the interrupt and the GPS device
  if(( Current_state.gps.pdop < 500)  && message_end)//&& ( Current_state.gps.pdop!=0)
  {
    GPS_done = 1;
    
    ///* Switch off the interrupt
    UCSR0B &= ~(_BV(RXCIE0));
    
    ///* Switch off the GPS device
    //power_down_peripheral(PGPS);
    
     Current_state.gps.pdop = 0xFFFF;
    message_end = 0;
    buffer = 0;
  }
}