//------------------------------------------------------------------------------------------------------
// Lab4 - C and Interrupts
// 1)Enalbe the interrupt for UART
// 2)Go to sleep mode
// 3)On interruption, echo back to the UART
//------------------------------------------------------------------------------------------------------
#include <stdio.h>

#define AHB_LED_BASE				0x50000000
#define AHB_UART_BASE				0x51000000
#define NVIC_INT_ENABLE			0xE000E100

volatile static int counter=0x31;

void UART_ISR()
{
	char c;
	c=*(volatile unsigned char*) AHB_UART_BASE;		//read a character from UART
	*(volatile unsigned char*) AHB_UART_BASE = c;	//write the character to UART
}


//////////////////////////////////////////////////////////////////
// Main Function
//////////////////////////////////////////////////////////////////

int main(void) {
	volatile int i;
	int delay = 400000;
	
	 printf("\n\rWelcome to ARM LTD\n\r");
	
  *(unsigned int*) NVIC_INT_ENABLE = 0x00000002;		//Enable interrupts for UART
	*(volatile unsigned int*) AHB_LED_BASE = 0xAA;
	
while(1){
		
		// Do some processing before entering Sleep Mode
		
  	*(volatile unsigned int*) AHB_LED_BASE = ~ *(volatile unsigned int*) AHB_LED_BASE;
		for(i=0;i<delay;i++);
		*(volatile unsigned int*) AHB_LED_BASE = ~ *(volatile unsigned int*) AHB_LED_BASE;
		for(i=0;i<delay;i++);
		*(volatile unsigned int*) AHB_LED_BASE = ~ *(volatile unsigned int*) AHB_LED_BASE;
		for(i=0;i<delay;i++);
		
	  printf("\n\rSend a Character: ");
		// Enter Sleep MODE
		__wfi();
	}
}