RE: [avr-gcc-list] basic UART Transmit interrupt problem

[Woodward, Mark P]

Hi All,

I just realized that my problem with interrupts is a general one.  The
program resets, whenever any interrupt is triggered.  I have read the
documentation thoroughly, and I am sure that I am using the proper
interrupt, (SIG_UART0_TRANS in the example below).  I would really
appreciate any help.  thank-you.

-Mark

> -----Original Message-----
> From: Woodward, Mark P 
> Sent: Thursday, July 03, 2003 11:01 AM
> To:   'Darren P'; address@hidden
> Subject:      RE: [avr-gcc-list] basic UART Transmit interrupt problem
> 
> Hi Darren,
> 
> I should have mentioned it before, but SIG_UART0_TRANS gives me exactly
> the
> same behavior.  Your reasoning does make sense though.  The pointer to my
> interrupt routine must be getting written over somehow.  Am I perhaps
> compiling incorrectly?  Here is my compilation procedure
> 
> avr-gcc -g -Os -mmcu=atmega128 -c -o Test.o Test.c
> avr-gcc -o Test.elf Test.o
> avr-objcopy -O srec Test.elf Test.srec
> uisp --erase -dprog=dapa
> uisp --upload -dprog=dapa if=Test.srec
> 
> I really appreciate your help.  Again, any suggestions would be greatly
> appreciated.
> 
> best,
> 
> -Mark
> 
> > -----Original Message-----
> > From:       Darren P [SMTP:address@hidden
> > Sent:       Wednesday, July 02, 2003 7:42 PM
> > To: Woodward, Mark P; address@hidden
> > Subject:    RE: [avr-gcc-list] basic UART Transmit interrupt problem
> > 
> > Hi,
> > Your problem is that you have not defined the ISR correctly, "SIGNAL(
> > SIG_UART_TRANS )" should be "SIGNAL( SIG_UART0_TRANS )", you must
> specify
> > which UART the ISR is for (there are 2 UARTs in the Mega128).
> > 
> > The reason the uC would restart is because gcc places "jmp 0x0000" (jump
> > to
> > the reset vector) at vector locations where no ISR has been defined.
> > 
> > Regards,
> > Darren
> > 
> > > Hello all,
> > >
> > > I run an atmega128L and am currently trying to transmit to the uart
> > using
> > > the transmit interrupt.  The problem is, when I send a byte after
> > enabling
> > > the transmit interrupt via
> > >
> > >   UCSR0B = (1<<TXEN)|(1<<TXCIE);
> > >   udr0 = 'A';
> > >
> > > the byte gets sent, but then the program restarts from main, without
> > > triggering my interrupt.  It's weird behavior.  Any help would be
> > greatly
> > > appreciated.  Here is the code.
> > >
> > > #include <avr/interrupt.h>
> > > #include <avr/io.h>
> > > #include <avr/signal.h>
> > >
> > > static volatile unsigned char *uart_data_ptr;
> > > static volatile unsigned char uart_counter;
> > > static volatile unsigned char led;
> > >
> > > SIGNAL( SIG_UART_TRANS ) {
> > >   uart_data_ptr++;
> > >
> > >   if(--uart_counter)
> > >     outp(*uart_data_ptr, UDR0);
> > > }
> > >
> > > void setRedLed(int on) {
> > >   if(on) {
> > >     cbi(PORTA, 2);
> > >   } else {
> > >     sbi(PORTA, 2);
> > >   }
> > > }
> > >
> > > void initRedLed(void) {
> > >   sbi(DDRA, 2);
> > >   setRedLed(0);
> > > }
> > >
> > > //I am transmitting at 57600
> > > void init(void) {
> > >   UBRR0H = 0;
> > >   UBRR0L = 15;
> > >
> > >   UCSR0A = 1<<U2X;
> > >
> > >   UCSR0B = (1<<TXEN)|(1<<TXCIE);
> > >
> > >   UCSR0C = (1<<UCSZ1)|(1<<UCSZ0);
> > > }
> > >
> > > void uart_send(unsigned char *buf, unsigned char size) {
> > >   if(!uart_counter) {
> > >     uart_counter = size;
> > >     uart_data_ptr = buf;
> > >     UDR0 = *buf;
> > >     // CRASHES HERE AND JUMPS BACK TO MAIN,
> > >     // THE BYTE DOES GET SENT
> > >     // DOESN'T CRASH IF I DON'T ENABLE TXCIE
> > >   }
> > > }
> > >
> > > int main(void) {
> > >   unsigned char i, j, k, l, m;
> > >
> > >   initRedLed();
> > >
> > >   // Debug to know restarted
> > >   led = 0;
> > >   for(m=0; m<10; m++) {
> > >     setRedLed(!led);
> > >     led = ~led;
> > >     for(i=0; i<255; i++)
> > >       for(j=0; j<255; j++)
> > >         for(l=0; l<100; l++)
> > >           k++;
> > >   }
> > >
> > >   init();
> > >   sei();
> > >
> > >   uart_send("HELLO WORLD", 12);
> > >
> > >   for(;;) { k++; }
> > > }
> > >
> > > _______________________________________________
> > > avr-gcc-list mailing list
> > > address@hidden
> > > http://www.avr1.org/mailman/listinfo/avr-gcc-list
> > 
> 
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