// DMA channel
#define DMA_CHANNEL		UDMA_CHANNEL_TMR0A
// buffer size
#define DMA_BUF_SIZE	100

// quantisation frequency
unsigned long ulFrequency = 8000;

// input buffer to store values from port D
uint16_t gpio_buf[DMA_BUF_SIZE];

// this is necessary
#pragma data_alignment=1024
unsigned char ucControlTable[1024];

// -------------------------- subroutines ----------------------------------

void timer_init()
{
	unsigned long ulPeriod;

    // switch TIMER clock on
	SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
	// full width timer
	TimerConfigure(TIMER0_BASE, TIMER_CFG_32_BIT_PER);
	// calculate the period
	ulPeriod = (80000000UL / ulFrequency);
	TimerLoadSet(TIMER0_BASE, TIMER_A, ulPeriod - 1);
}

void timer_enable()
{
	// enable my timer
	TimerEnable(TIMER0_BASE, TIMER_A);
}

void dma_init(void)
{
	// fill the buffer with a constant: I can watch transactions in the WatchWindow
	memset(gpio_buf, 0xFF, sizeof(gpio_buf));
	
	// enable of the monitoring port
	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    GPIOPinTypeGPIOInput(GPIO_PORTD_BASE, GPIO_PIN_0 | GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3);

    // switch DMA clock on
    SysCtlPeripheralEnable(SYSCTL_PERIPH_UDMA);
    uDMAEnable();
    uDMAControlBaseSet(ucControlTable);
	
    // fill attributes
    uDMAChannelAttributeDisable(DMA_CHANNEL,
    		UDMA_ATTR_ALTSELECT
    		| UDMA_ATTR_USEBURST
    		| UDMA_ATTR_REQMASK
    		| UDMA_ATTR_HIGH_PRIORITY);

    // primary transaction set
    uDMAChannelControlSet(DMA_CHANNEL | UDMA_PRI_SELECT,
    		UDMA_SIZE_16 |				// word size
    		UDMA_SRC_INC_NONE |			// from register (GPIO_PORTD_BASE + GPIO_O_DATA) so constant
    		UDMA_DST_INC_16 |			// destination in memory so increment
    		UDMA_ARB_1);				// one word per transaction
   	// primary transfer set
    uDMAChannelTransferSet(DMA_CHANNEL | UDMA_PRI_SELECT,
    		UDMA_MODE_BASIC,			// linear filling
            (void *)(GPIO_PORTD_BASE + GPIO_O_DATA),	// GPIOD data register
            gpio_buf,					// my buffer
            DMA_BUF_SIZE);				// buffer size
  
	// enable DMA - waiting for the trigger event
    uDMAChannelEnable(DMA_CHANNEL);
}

// ------------------------- main application function -----------------------------
void board_init()
{
	timer_init();	// setup a timer - it doesn't work now
	dma_init();		// setup DMA - it suspend for some events
	timer_enable();	// start my timer - since that all transactions happen

	IntMasterEnable();
}