Arduino Serial Interrupts

Question

I am working on an Arduino Mega 2560 project. At a Windows 7 PC I am using the Arduino1.0 IDE. I need to establish a serial Bluetooth communication with a baud rate of 115200. I need to receive an interrupt when data is available at RX. Every piece of code I have seen use “polling”, which is placing a condition of Serial.available inside Arduino’s loop. How can I replace this approach at Arduino’s loop for an Interrupt and its Service Routine? It seems that attachInterrupt() does not provides for this purpose. I depend on an Interrupt to awake the Arduino from sleep mode.

I have developed this simple code that is supposed to turn on a LED connected to the pin 13.

    #include <avr/interrupt.h> 
    #include <avr/io.h> 
    void setup()
    {
       pinMode(13, OUTPUT);     //Set pin 13 as output

       UBRR0H = 0;//(BAUD_PRESCALE >> 8); // Load upper 8-bits of the baud rate value into the high byte of the UBRR register 
       UBRR0L = 8; // Load lower 8-bits of the baud rate value into the low byte of the UBRR register 
       UCSR0C |= (1 << UCSZ00) | (1 << UCSZ10); // Use 8-bit character sizes 
       UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);   // Turn on the transmission, reception, and Receive interrupt      
    }

    void loop()
    {
      //Do nothing
    }

    ISR(USART0_RXC_vect)
    {    
      digitalWrite(13, HIGH);   // Turn the LED on          
    }

The problem is that the subroutine is never served.

Answer 1

Just after UBRR0L = 8 instead of this:

 UCSR0C |= (1 << UCSZ00) | (1 << UCSZ01);

change to this:

 UCSR0C |= (1 << UCSZ00) | (1 << UCSZ10);

Answer 2

Finally I have found my problem. I changed the interruption vector "USART0_RXC_vect" by USART0_RX_vect. Also I added interrupts(); to enable the global interrupt and it is working very well.

The code is:

#include <avr/interrupt.h> 
#include <avr/io.h> 
void setup()
{
   pinMode(13, OUTPUT); 

   UBRR0H = 0; // Load upper 8-bits of the baud rate value into the high byte of the UBRR register 
   UBRR0L = 8; // Load lower 8-bits of the baud rate value into the low byte of the UBRR register 
   UCSR0C |= (1 << UCSZ00) | (1 << UCSZ10); // Use 8-bit character sizes 
   UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);   // Turn on the transmission, reception, and Receive interrupt      
   interrupts();
}

void loop()
{

}

ISR(USART0_RX_vect)
{  
  digitalWrite(13, HIGH);   // set the LED on
  delay(1000);              // wait for a second
}

Thanks for the replies!!!!

Answer 3

Did you try that code and it didn’t work? I think the problem is that you haven’t turned on interrupts. You could try calling sei(); or interrupts(); in your setup function.