Interrupt Nios II RS232 / Usart

Hello!

I am trying to use the rs232 interrupt. sending and receiving data works fine, but when i try to use the interrupt to receive data I get some problems.

this is the rs232 block in my system.h

/*

* uart_rs232 configuration

*

*/

# define UART_RS232_NAME "/dev/uart_rs232"

# define UART_RS232_TYPE "altera_avalon_uart"

# define UART_RS232_BASE 0x0a201280

# define UART_RS232_SPAN 32

# define UART_RS232_IRQ 18

# define UART_RS232_IRQ_INTERRUPT_CONTROLLER_ID 0

# define UART_RS232_BAUD 9600

# define UART_RS232_DATA_BITS 8

# define UART_RS232_FIXED_BAUD 0

# define UART_RS232_PARITY 'N'

# define UART_RS232_STOP_BITS 1

# define UART_RS232_SYNC_REG_DEPTH 2

# define UART_RS232_USE_CTS_RTS 0

# define UART_RS232_USE_EOP_REGISTER 0

# define UART_RS232_SIM_TRUE_BAUD 0

# define UART_RS232_SIM_CHAR_STREAM ""

# define UART_RS232_RELATIVEPATH 0

# define UART_RS232_FREQ 100000000

# define ALT_MODULE_CLASS_uart_rs232 altera_avalon_uart

//this is my context

typedef struct

{

int number;

}my_context;

//This is my ISR

void rs232_isr (void* context, alt_u32 interrupt_number)

{

printf("data gets in");

}

//this I call in my main at first

void main(){

char msg[4]="test";

int result;

result=alt_irq_register (UART_RS232_IRQ,

(void*)my_contex,

rs232_isr);

alt_irq_enable(UART_RS232_IRQ);

do{

fp = fopen("/dev/uart_rs232", "w+");

if(fp)

{

//printf("Connected\n");

fwrite(msg, strlen(msg), 1, fp);

//fprintf(fp, "Closing the UART file.\n");

fclose(fp);

}

else

{

printf("Error/dev/ttyS0\n");

}

}while(1);

}

If I start the my program the rs232_isr is called I think one hundred times...

I think the rs232_isr is called by the fwrite(..). Is there a method to recognize only the RXD without react everytime at TXD (text send).