implements two mcp4921 DACs for dual audio output (TM4C123)

spi.c

/*
 * spi.c
 *
 *  Created on: Mar 15, 2016
 *      Author: joseph
 */
#include <stdint.h> // Variable definitions for the C99 standard.
#include <stdio.h> // Input and output facilities for the C99 standard.
#include <stdlib.h>
#include <stdbool.h> // Boolean definitions for the C99 standard.
#include <math.h>

#include "inc/tm4c123gh6pm.h" // Definitions for the interrupt and register assignments.
#include "inc/hw_memmap.h" // Memory map definitions of the Tiva C Series device.
#include "inc/hw_types.h" // Definitions of common types and macros.
#include "inc/hw_ssi.h"

#include "driverlib/sysctl.h" // Definitions and macros for System Control API of DriverLib.
#include "driverlib/interrupt.h" // Defines and macros for NVIC Controller API of DriverLib.
#include "driverlib/gpio.h" // Definitions and macros for GPIO API of DriverLib.
#include "driverlib/timer.h" // Defines and macros for Timer API of DriverLib.
#include "driverlib/pin_map.h" //Mapping of peripherals to pins for all parts.
#include "driverlib/uart.h" // Definitions and macros for UART API of DriverLib.
#include "driverlib/adc.h" // Definitions for ADC API of DriverLib.
#include "driverlib/fpu.h" // Prototypes for the FPU manipulation routines.
#include "driverlib/ssi.h" // Definitions and prototypes for the SSI/SPI routines.

#include "utils/uartstdio.h" // Prototypes for the UART console functions.
							 // Needs to add "utils/uartstdio.c" through a relative link.

#define ADC0_SEQ_NUM 0
#define spi_freq	44100
#define CS1   GPIO_PIN_0
#define CS2   GPIO_PIN_1
#define tx1    GPIO_PIN_2
#define tx2    GPIO_PIN_3
#define LDAC    GPIO_PIN_4
#define sck		GPIO_PIN_5
#define SPI_DATA_MASK    0x0FFF
#define SPI_CTRL_MASK    0x7000

uint32_t sys_clock;
uint32_t i;
uint32_t D[8];
uint16_t data1[16];
uint16_t data2[16];
uint16_t dummy1;
uint16_t dummy2;
uint16_t bit[16] = {
		0x0001,
		0x0002,
		0x0004,
		0x0008,
		0x0010,
		0x0020,
		0x0040,
		0x0080,
		0x0100,
		0x0200,
		0x0400,
		0x0800,
		0x1000,
		0x2000,
		0x4000,
		0x8000
};

void timer0_spi(void);
void init_pins(void);
void init_ADC(void);
void init_timers(void);

int main(void)
{
	SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
	sys_clock = 80000000;

	init_pins();
	init_ADC();
	init_timers();
	timer0_spi();

	IntMasterEnable();
	TimerEnable(TIMER0_BASE, TIMER_A);
}

void init_pins(void)
{
	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
	// chip selects, transmit signals, LOAD DAC, sck
	GPIOPinTypeGPIOOutput(GPIO_PORTB_BASE, CS1 | CS2 | tx1 | tx2 | LDAC | sck);
	//initialize pin values
	GPIOPinWrite(GPIO_PORTB_BASE, sck, 0);
	GPIOPinWrite(GPIO_PORTB_BASE, CS1, CS1);
	GPIOPinWrite(GPIO_PORTB_BASE, CS2, CS2);
	GPIOPinWrite(GPIO_PORTB_BASE, LDAC, LDAC);
	GPIOPinWrite(GPIO_PORTB_BASE, tx1, 0);
	GPIOPinWrite(GPIO_PORTB_BASE, tx2, 0);

}

void init_timers(void)
{
		SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
		TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC);
		TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/spi_freq -1);
		IntRegister(INT_TIMER0A, timer0_spi);
		IntEnable(INT_TIMER0A);
		TimerIntEnable(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
}

void init_ADC(void)
{
	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);

	SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);

	GPIOPinTypeADC(GPIO_PORTD_BASE, GPIO_PIN_0);
	GPIOPinTypeADC(GPIO_PORTD_BASE, GPIO_PIN_1);

	ADCSequenceConfigure(ADC0_BASE, ADC0_SEQ_NUM, ADC_TRIGGER_PROCESSOR, 0);
	ADCSequenceStepConfigure(ADC0_BASE, ADC0_SEQ_NUM, 0, ADC_CTL_CH7);
	ADCSequenceStepConfigure(ADC0_BASE, ADC0_SEQ_NUM, 1, ADC_CTL_IE | ADC_CTL_END | ADC_CTL_CH6);
	ADCSequenceEnable(ADC0_BASE, ADC0_SEQ_NUM);
}

void timer0_spi(void)
{
	ADCProcessorTrigger(ADC0_BASE, ADC0_SEQ_NUM);

						while(!ADCIntStatus(ADC0_BASE, ADC0_SEQ_NUM, false)) {}

						ADCIntClear(ADC0_BASE, ADC0_SEQ_NUM);

						ADCSequenceDataGet(ADC0_BASE, ADC0_SEQ_NUM, &D);

	TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	dummy1 = (D[0] & SPI_DATA_MASK) | SPI_CTRL_MASK;
	dummy2 = (D[1] & SPI_DATA_MASK) | SPI_CTRL_MASK;

	for(i=0; i<16; i++)
	{
		//create a vector of data from LSB to MSB and move value to ones place
		data1[i] = (dummy1 & bit[i]) >> i;
		data2[i] = (dummy2 & bit[i]) >> i;
	}
	//set CS1 on
	GPIOPinWrite(GPIO_PORTB_BASE, CS1, 0);
	for(i=0; i<16; i++)
	{
		//push data bits to DAC starting with MSB
		GPIOPinWrite(GPIO_PORTB_BASE, tx1, tx1*data1[15-i]);
		//sck pulse
		GPIOPinWrite(GPIO_PORTB_BASE, sck, sck);
		GPIOPinWrite(GPIO_PORTB_BASE, sck, 0);
	}
	//set CS1 off, set CS2 on
	GPIOPinWrite(GPIO_PORTB_BASE, CS1, CS1);
	GPIOPinWrite(GPIO_PORTB_BASE, CS2, 0);
	for(i=0; i<16; i++)
	{
		//push data bits to DAC starting with MSB
		GPIOPinWrite(GPIO_PORTB_BASE, tx2, tx2*data2[15-i]);
		//sck pulse
		GPIOPinWrite(GPIO_PORTB_BASE, sck, sck);
		GPIOPinWrite(GPIO_PORTB_BASE, sck, 0);
	}
	//chip select 2 is off
	GPIOPinWrite(GPIO_PORTB_BASE, CS2, CS2);
	//execute both DACs with LDAC
	GPIOPinWrite(GPIO_PORTB_BASE, LDAC, 0);
	GPIOPinWrite(GPIO_PORTB_BASE, LDAC, LDAC);
}