/****************************************************************************
 Module
  IMU_SERVICE_SPI pseudo code
/*----------------------------- Module Defines ----------------------------*/
#define READ_IMU_PERIOD 
#define BOOTING_PERIOD 
#define POWER_ON_PERIOD 

/*---------------------------- Module Variables ---------------------------*/
init a state variable
init a MyPriority;

init three byte variables to store data
init a flag to indicate that we are obtaining real data, instead of init steps 

set NUM_OF_DATA to 6, acceleration and gyro for X Y Z axes
set up array of int16_t to store the IMU data
set up a counter to populate the array
set up a counter to count the init steps

define the "read data commands", each consists of a "read mask" and the register address

set NUM_INIT_STEPS to 6
set up the two arrays, following startup sequence in chapter 3 of application note, and enable high pass filter


/*------------------------------ Module Code ------------------------------*/
/****************************************************************************

****************************************************************************/
bool InitIMU_Service_SPI ( uint8_t Priority )
{
  
  save our priority
	set CurrentState to POWER_ON_WAITING;

	init SPI
	kick off the timer to wait for the start up time
	update the flag indicating we are not receiving actual data
  return true;
}

/****************************************************************************

****************************************************************************/
bool PostIMU_Service_SPI( ES_Event ThisEvent )
{
  return ES_PostToService( MyPriority, ThisEvent);
}

/****************************************************************************

****************************************************************************/
ES_Event RunIMU_Service_SPI( ES_Event CurrentEvent )
{
  
   ES_Event ReturnEvent = { ES_NO_EVENT, 0 }; // assume no error


    switch ( CurrentState )
   {
			case POWER_ON_WAITING:
				
				if the READ_IMU_TIMER times out
					set CurrentState to BOOTING_IMU;
					kick off the timer again
				
						
				break;
		 
      case BOOTING_IMU:
				if READ_IMU_TIMER times out
									 
									 if the init steps have not yet finished
										 write the address of the Init register to SPI
										 write the value we want in that register to SPI
										 enable SPI Interupt
										 increment init step
				
										 kick off timer to give some time until the next step
										 

									 if we finished configuring all the steps
										 
										 set FlagDoingData to 1, indicating useful data are coming
										 clear the init step counter
										 set CurrentState to COMMANDING_IMU
										 kick off timer for real sensor reading

				break;
									 
			case COMMANDING_IMU:
								 if READ_IMU_TIMER times out
										if FlagDoingData is set to 1
											write the lower of the data register address to read the IMU data, 
										    followed by two 0x00 to SPI
											enable SPI Interupt

								 set CurrentState to RECEIVING_FROM_IMU;
                  break;

      

     case RECEIVING_FROM_IMU :      
               	if we have an ES_EOT event

							clear an int16_t data buffer 
							shift the data3 by 8 bit to the left, and combine that with data2 to form int16_t number
							store in the IMU data array
									
							increment IMU data counter
                  			start the timer for the next IMU read cycle
							set CurrentState to COMMANDING_IMU;

							break;
								
		 default:
			 break;
				 
	 }	 
        return (ReturnEvent);
}

/********************************************SPI FUNCTIONS********************************************/

void SPI_Init(void){
	Enable the clock to the GPIO Port (we are going to use Port D)
	Enable clock to SSI - set to SSI Module 3
	Wait for GPIO Port to be ready by killing a few cycles

	Program the GPIO to use the alternate functions on the SSI pins PD0,1,2,3
	Set Mux position in GPIOPCTL to select the SSI use of the pins
	
	Program the port lines for digital I/O	
	Program the required data directions on the port line
	
	program the pull-up on the clock line	
	Wait for the SSI3 to be ready	
	Make sure that the SSI is disabled before programming mode bits
	Select Master mode and TXRES indicating EOT
	Configure the SSI clock source to the system clock
	Configure the clock pre-scaler: here we want CPSDVSR =80 , 1+SCR = 61
	Configure  phase (SPH)- 1 and 
	polarity (SPO)- 1 ,mode (FRF) - freescale(0) and datasize (DSS) - 8 bit
	Locally Enable Interrupts (TXIM in SSIIM)
	enable SPI Interupt();
	Enable SSI3
	Globally enable interupts

	Enable the NVIC interrupt for the SSI when starting to transmit
	enable SSI3 interrupt in the NVIC, it is interrupt number 58 so appears in EN2 at bit 0
	make sure we disable loopback mode
}




static void enable_SPI_Interupt(void){
  set SSI_IM_TXIM;
}

static void disable_SPI_Interupt(void){
  clear SSI_IM_TXIM;
}

void SPI_Interupt_Response(void){
	
  disable SPI Interupt 
  read and store data, three times
	
	if we are doing data
	post an ES_EOT event to this service
	}

}


void SPI_Write(uint8_t data){
  Set the data to SPI register
}

// Read the data from SPI register
uint8_t SPI_Read(void){
  Read the data from SPI register
  return that data
}