[Simulavr-devel] UART Interrupt and Timer problem

[Jakob Schwendner]

Hi,

I have a problem with using the UART1 on a atmega128 simulation. My
application that is running fine on hardware seems to cause some
troubles in the simulator. The actual program was using the
procyon-avrlib for higher-level access to the uart. Using it caused
the simulation to stall after transmitting a byte. Changing the
baudrate changed it, but would still lead to unwanted behaviour.
I have created a small program that sets up the uart and sends bytes
with a delay to test for the behaviour. The debug output reveals that
it seems to be trapped in the IRQ. After the first byte has been
transmitted it would repeat the debug output from the irq handler.
Could there be a problem in the simulator with clearing the TXC
interrupt after it has been thrown?
On the same note, on my receiving end I am using a modified serialrx
class to listen to the UART1. Even with the irq problem I am having,
the first byte is being transmitted. However, for this to work I have
to set up the baudrate in the serialrx class to 2*19200 for it to
work.
My F_CPU is 16000000
I set up the simulation with
dev1->SetClockFreq(1000/16);

anything I am missing? Help would be greatly appreciated. 
btw.: Great code! Very easy to read.

//----- Include Files ---------------------------------------------------------
#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>

#include "global.h"

#define UART1_BAUD  19200

//----- Begin Code ------------------------------------------------------------

volatile u08   uartReadyTx;

int main(void)
{
   // set LED pins for output
   DDRA = _BV(DDA2) | _BV(DDA4);        

   // set BAUD rate for UART1
   UBRR1L = ((F_CPU+(UART1_BAUD * 8L))/(UART1_BAUD * 16L)-1);
   UBRR1H = 0;

   // init UART1 and enable TXC interupt
   UCSR1B = BV(TXEN)|BV(TXCIE); 

   uartReadyTx = 0;

   // enable all interupts
   sei();

   while(1) {
      // wait for uart to be ready
      while( uartReadyTx );

      // delay
      int m = 33000;
      while( m-- );

      // send byte through uart
      UDR1 = 0x55;
      // set uart not ready
      uartReadyTx = 1;

      // debug
      sbi( PORTA, PA2);
      cbi( PORTA, PA2);         
   }

   return 0;
}

INTERRUPT(SIG_UART1_TRANS)      
{
   // debug
   sbi( PORTA, PA4);
   cbi( PORTA, PA4);            

   // set uart ready
   uartReadyTx = 0;     
}