receive interrupt in USART0 - AT91SAM7X256

/*-------------------------------------------------------------------------------
    USART0 receive interrupt  
--------------------------------------------------------------------------------*/
/*-------------------------------------------------------------------------------

8 bits
Baud rate : 9600
--------------------------------------------------------------------------------*/

#include <AT91SAM7X256.H> 
//#include <intrinsics.h>
#include <stdio.h>
#include "delay.h"
#include "usart.h"

//#include "irq_enable.h"
//#include "usart.h"
//#include "aic.h"


#define LCD_PORT_A           //CHAR LCD pins definition
#define LCD_RS  3
#define LCD_E   5
#define LCD_DB4 6
#define LCD_DB5 7
#define LCD_DB6 8
#define LCD_DB7 9

#include "lcd.h"

void usart0_irq_handler(void) __irq; // function prototype for USART0 handler


//global variables
float d;
char buffer[]={0,0,0,0,0};







int main ()
{
	//*AT91C_PMC_PCER = (1<<AT91C_ID_IRQ0 );
	AT91C_BASE_PIOB->PIO_PER = (1<<27)|(1<<28);
	AT91C_BASE_PIOB->PIO_OER = (1<<27)|(1<<28);
	AT91C_BASE_PMC->PMC_PCER = (1<<AT91C_ID_US0);  // step1: activate usart0 clock
	AT91C_BASE_PIOA->PIO_PDR = AT91C_PA0_RXD0 | AT91C_PA1_TXD0; //step2: disable I/O pin on PA0  and  PA1
	AT91C_BASE_PIOA->PIO_ASR = AT91C_PIO_PA0 | AT91C_PIO_PA1;   //step3: activate peripheral A select register for PA0 and PA1  for using usart0 on this pin
	AT91C_BASE_PIOA->PIO_BSR = 0;                               //step4: disable peripheral B 
	// At this point, we have the USART0 peripheral clock turned on and the two pins (RXD0 and TXD0 ) are
 //associated with the USART0 peripheral.
	
	// Set up the Advanced Interrupt Controller (AIC) registers for USART0	

	AT91C_BASE_AIC->AIC_IDCR = (1<<AT91C_ID_US0);   // Disable USART0 interrupt in AIC
	AT91C_BASE_AIC->AIC_SVR[AT91C_ID_US0] = (unsigned int)usart0_irq_handler; // Set the USART0 IRQ handler address in AIC 
	AT91C_BASE_AIC->AIC_SMR[AT91C_ID_US0] =(AT91C_AIC_SRCTYPE_INT_HIGH_LEVEL | 0x4 ); // Set the int source type and pri 
	AT91C_BASE_AIC->AIC_IECR = (1<<AT91C_ID_US0);  // Enable the USART0 interrupt in AIC
	
	
// Control Register - Reset then Disable the Receiver/Transmitter
	AT91C_BASE_US0->US_CR = AT91C_US_RSTRX |  // reset receiver
                          AT91C_US_RSTTX | // reset transmitter
                          AT91C_US_RXDIS | // disable receiver
                          AT91C_US_TXDIS; // disable transmitter
	
	
	AT91C_BASE_US0->US_MR = (AT91C_US_PAR_NONE | 0x3 << 6); // no parity  8-bit characters
	AT91C_BASE_US0->US_IER = 0x0000;
	AT91C_BASE_US0->US_IDR = 0xFFFF;
	AT91C_BASE_US0->US_BRGR= 0x138; // CD = 0x138 (312 from  calculation)    FP=0 (not used) 
	AT91C_BASE_US0->US_RTOR= 0; // receiver time-out (disabled)
	AT91C_BASE_US0->US_TTGR= 0; // transmitter timeguard (disabled)
	AT91C_BASE_US0->US_FIDI= 0; // FI over DI Ratio Value (disabled)
	AT91C_BASE_US0->US_IF= 0; // IrDA Filter value (disabled)
	
	
	


// Final Preparations for USART0 Interrupt Processing


	AT91C_BASE_US0->US_CR = AT91C_US_RXEN | AT91C_US_TXEN ;    // enable the USART0 receiver 
	AT91C_BASE_US0->US_IER = AT91C_US_RXRDY;   // enable RXRDY usart0 receive interrupt
	AT91C_BASE_US0->US_IDR = ~AT91C_US_RXRDY;  // disable all other interrupts except RXRDY
	AT91C_BASE_AIC->AIC_IECR = (1<<AT91C_ID_US0);

	
	while(1){
			//while((*AT91C_US0_CSR&2)!=2);	 //  wait till usart gets ready for send
			//*AT91C_US0_THR=d+15;
			*AT91C_PIOB_SODR = (1<<28);
			delay_ms(2000);
		  *AT91C_PIOB_CODR = (1<<28);
			delay_ms(2000);
		
		
		
				lcd_gotoxy(1,1); 
				lcd_putsf("Recieved data :");
		
				sprintf(buffer,"%f",d);
				lcd_gotoxy(2,1);
				lcd_putsf(buffer);
				delay_ms(1000);
			

}
	
	
	
	
	
}

void usart0_irq_handler(void) __irq {
	volatile unsigned int dummy;
		AT91C_BASE_AIC->AIC_EOICR = AT91C_BASE_US0->US_CSR;
		dummy = AT91C_BASE_AIC->AIC_IVR;
				*AT91C_PIOB_SODR = (1<<27);
			  delay_ms(500);
		   *AT91C_PIOB_CODR = (1<<27);
			  delay_ms(500);
//if ((AT91C_BASE_US0->US_CSR & AT91C_US_RXRDY) == AT91C_US_RXRDY) {
// we have a receive interrupt, 

		 d = getkey();
	   d = d+15;
			
	  sendchar(d);
	 AT91C_BASE_AIC->AIC_ICCR  = (1 << AT91C_ID_US0);
   
	 AT91C_BASE_AIC->AIC_EOICR=0;
	
		//}
}