#include <p18F452.h>
#include <delays.h>
#include <stdio.h>
#include <usart.h>

#include "samples_table.h"

// from the CCS C compiler suite
#define bitset(var,bitno) ((var) |= 1 << (bitno))
#define bitclr(var,bitno) ((var) &= ~(1 << (bitno)))

/* Set up the configuration bits */
#pragma config OSC = HS
#pragma config PWRT = OFF
#pragma config BOR = OFF
#pragma config WDT = OFF
#pragma config LVP = OFF

#define BAUD 9600
#define FOSC 20000000L

#define HIGH_LIMIT 200
#define LOW_LIMIT 80
#define MIPS 5
#define LOW_PULSE_PERIOD (500L) // in ms
#define HIGH_PULSE_PERIOD (100L) // in ms
#define	LOW_PULSE_COUNT (0xFFFF - (LOW_PULSE_PERIOD*MIPS*1000L)/256L)
#define	HIGH_PULSE_COUNT (0xFFFF - (HIGH_PULSE_PERIOD*MIPS*1000L)/256L)

void SPI_setup(void)
{
	// Set RA2 for output (Chip Select) 
	TRISDbits.TRISD0 = 0;

	// Device select (1 -> not selected);
	PORTDbits.RD0 = 1;

	// Set RC5 for output (SDO)
	TRISCbits.TRISC5 = 0;
	// Set RC3 for output (SCK)
	TRISCbits.TRISC3 = 0;
	
	// Disable the SPI subsystem
	SSPCON1bits.SSPEN = 0;
	// Sample setting
	SSPSTATbits.SMP = 1;
	// Set the bus mode 1,1
	SSPSTATbits.CKE = 0;
	SSPCON1bits.CKP = 1;
	// Clear the collision detection
	SSPCON1bits.WCOL = 0;
	// SPI Master at Fosc/16
	SSPCON1 = ((SSPCON1 & 0b11110000) | 0b00000001);
	// SPI module is on
	SSPCON1bits.SSPEN = 1;
}

void send_SPI(unsigned short data)
{
	unsigned char first_byte;
	unsigned char second_byte;

	// data (4 MSb)
	first_byte = ((data >> 8) & 0b00001111);

	// select A unit;
	bitclr(first_byte,7);

	// Set gain to 2
	bitclr(first_byte,5);

	// !SHDN
	bitset(first_byte,4);

	// Data (8 LSb)
	second_byte = (data) & 0b11111111;

	// Device select (0 -> selected)
	PORTDbits.RD0 = 0;

	// Send first byte
	SSPBUF = first_byte;
	while (SSPSTATbits.BF == 0);

	// Send second byte
	SSPBUF = second_byte;
	while (SSPSTATbits.BF == 0);

	// Device select (1 -> not selected)
	PORTDbits.RD0 = 1;	
} 

void main( void)
{
	unsigned char first_byte;
	unsigned char second_byte;
	unsigned char current_sample;
	unsigned int sample_value;

	// setup SPI
	SPI_setup();

	// select A unit;
	bitclr(first_byte,7);	
	// Set gain to 2
	bitclr(first_byte,5);
	// !SHDN
	bitset(first_byte,4);
	
	// Loop forever
	current_sample = 0;
		
	while (1)
	{
		sample_value = samples_table_16[current_sample++];

		// data (4 MSb)
		first_byte = (first_byte & 0b11110000) | ((sample_value >> 8) & 0b00001111);		

		// Data (8 LSb)
		second_byte = (sample_value) & 0b11111111;

		// Device select (0 -> selected)
		PORTDbits.RD0 = 0;

		// Send first byte
		SSPBUF = first_byte;
		while (SSPSTATbits.BF == 0);	

		// Send second byte
		SSPBUF = second_byte;
		while (SSPSTATbits.BF == 0);

		// Device select (1 -> not selected)
		PORTDbits.RD0 = 1;
	}
}