//****************************************************************
//Title:    10 BIT DAC USING SPI1 TO LTC1661                     *
//          implementing math.h for float opaerations            *
//Authors:  Travis Chandler (based on Chapters 13 and 16 
//	    of Mazidi & Causey HCS12 textbook 			 *
//          Shujen Chen (converted to Tower 02/07/2013           *
//Date:     03-19-10 and 02-07-2013                              *
//Platform: Freescale TWR-S12G128 + Axiom TWR-DEV-PERIPH         *
//          HCS12 MC9S12G128                                     *
//Compiler: Feescale CodeWarrior IDE v5.9.0                      *
//          Build 5294 1993-2007                                 *
//          Freescale Semiconductor, Inc.                        *
//Description: Closed loop sending 1 kHz sine wave to            *
//             peripheral board LTC1661 via SPI1                 *
//             output to DAC A/B. 				 *
//Use Scope to see the sinewave output                           *
//****************************************************************
//When creating project in CodeWarrion, make sure you choose:
//minimal setup code,
//small, AND
//float is IEEE32. double is IEEE32
//Last modified by Mazidi (8-05-2013)
 
#include <hidef.h>                                              //common defines and macros
#include "derivative.h"                                         //derivative-specific definitions */
#include <math.h>                                               //
#define frequency 1000                                          //FLOATING POINT DEFINES AND MACROS
#define Samples_per_period  40000/frequency                     //CHANGE THIS TO CHANGE SAMPLE FREQUENCY
void SPI_ini(void);                                             //
                                                                //
void main(void){
	double my_double;                                           //VARIABLE TO HOLD FLAOTING POINT DATA
	unsigned int i, my_int;                                     //VARIABLE TO HOLD INT CONVERTIONS OF FLOATING POINT DATA
	unsigned char msb, lsb;
	unsigned int int_array[Samples_per_period];                 //GLOBAL ARRAY TO HOLD LOOKUP TABLE

	SPI_ini();
	for(i = 0; i  <Samples_per_period; i++){                    //INITIALIZE LOOK UP TABLE
        my_double = (2 * _M_PI * i);                            //
        my_double /= (Samples_per_period);                      //_M_PI FROM MATH.H RETURNS PI
        my_double = sin(my_double);                             //SIN(RADIANS) FROM MATH.H
        my_double *= 511;                                       //
        my_double += 512;                                       //ADD OFFSET ADC DOES NOT USE NEGATIVES
        my_int = (int)my_double;                                                           
        int_array[i] = my_int;
	}

	for(;;){
        for(i = 0; i < Samples_per_period; i++){
            my_int = int_array[i];
            lsb = my_int & 0x003F;                  //MASK LSB
            lsb = lsb << 2;                         //Bits 1 AND 0 ARE IGNORED BY LTC1661 SO 6 LSB OF 10 BIT MUST ME SHIFTED LEFT 2
            my_int = my_int >> 6 ;                  //POSITION MSB OF 10 BIT TO BE MASKED
            msb = my_int & 0x000F;                  //GET MSB OF 10 BIT DAC
                                                    //BITS 15, 14, 13, AND 12 ARE CMD FOR LTC1661
            msb |= 0xF0;                            //Ah IS THE LTC1661 CMD TO WRITE TO DAC B AND UPDATE THE OUTPUT
                                                    //CHANGE TO 0x90 TO SEND TO DACA
                                                    //OR 0xF0 TO SEND SAME DATA TO BOTH DAC A AND B
            PTJ_PTJ3 = 0;                           //SET CS LOW TO START 16 BIT TRANSFER

			while (!SPI1SR_SPTEF);					// wait until data reg empty    
			SPI1DR = msb;							// sends out a character onto the MOSI pin
			while (!SPI1SR_SPIF);					// wait for 8-bits to shift out     
			msb = (unsigned char)SPI1DR;			// dummy read to reset SPIF flag  
			while (!SPI1SR_SPTEF);					// wait until data reg empty    
			SPI1DR = lsb;							// sends out a character onto the MOSI pin
			while (!SPI1SR_SPIF);					// wait for 8-bits to shift out      
			lsb = (unsigned char)SPI1DR;			// dummy read to reset SPIF flag  
 
            PTJ_PTJ3 = 1;                           //SET CS LOW TO END TRANFER SESSION
        }
    }
}

void SPI_ini(void){
	DDRJ_DDRJ3 = 1;									//PORTJ 1 IS USED FOR CS OF LTC1661
	PTJ_PTJ3 = 1;		// slave select pin			//SET CS HIGH IT IS ACTIVE LOW 
    SPI1BR = 0x00;                                  //0x00 => 6.25Mhz/1 = 6.25Mhz
                                                    //BUS CLOCK 6.25MHZ / ((SPPR + 1) * 2^(SPR +1))
    SPI1CR1 = 0x50;                                 //SPI INTERUPT DISABLED
                                                    //ENABLE SPI PORT CONFIGURE AS SERIAL PORT
                                                    //MASTER MODE
                                                    //NON INVERTED CLOCK, IDLES LOW
                                                    //DATA SAMPLE AT RISING EDGE
                                                    //FIRST CLOCK EDGE DELAY 1/2 CYCLE 
                                                    //DATA TRANSFERD MSB FIRST
    SPI1CR2 = 0x0;                                  //DEFAULT IS 0, INITIALIZATION IS OPTIONAL
}