Re: [avr-gcc-list] Interrupt Driven UART

[Asim]

Thanks for the reply.
I tried enabling and disabling the UDRIE, but still no response, the list
file shows the correct interrupt vectors and the interrupts are enabled
properly. I tried disabling the transmitter completely, there is no
response from the receiver side.

Thanks



Larry Barello wrote:

> If nothing is happening then you must not have (the correct) interrupts
> enabled or the system is crashed.  Have you tried running this in the
> simulator?
>
> Some obvious problems: You must have UDRIE  off until there is data in the
> output queue.  So, 1) Enable UDRIE every time you put a character in the
> output queue and 2) disable UDRIE whenever the UDRE interrupt handled has
> nothing to do (ie. in the handler if the queue is empty, turn it off and
> then return).  Otherwise your code will endlessly loop servicing the UDRIE
> interrupt, since the UDR is *always* ready.
>
> Don't use TXCIE.  Leave RCXIE on all the time.
>
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden Behalf Of Asim
> Sent: Sunday, August 29, 2004 3:51 AM
> To: address@hidden
> Subject: [avr-gcc-list] Interrupt Driven UART
>
> Hi there.
>
> I tried the following code to test the uart interrupts on Mega8535,
> but there is no response either from TX and RX, while if I use the
> polling mode then there is no problem, any help.
>
> Thanks
>
> /*----------------------------------------------------------*
>   Interrupt Driven Uart Test
>
>   MEGA8535 Fuses Setting
>   ----------------------
>   S8535C  =1     BODLEVEL =0
>   WDTON   =1     BODEN    =0
>   SPIEN   =1     SUT1     =0
>   CKOPT   =0     SUT0     =1
>   EESAVE  =1     CKSEL3   =1
>   BOOTSZ1 =1     CKSEL2   =0
>   BOOTSZ0 =1     CKSEL1   =1
>   BOOTRST =1     CKSEL0   =0
>
>   0=Programmed
>  *----------------------------------------------------------*/
>
> #include    <avr/io.h>
> #include    <avr/interrupt.h>
> #include    <avr/signal.h>
> #include    <avr/pgmspace.h>
> #include    <avr/delay.h>
> #include    <stdio.h>
>
> #define uc              unsigned char
> #define ui              unsigned int
>
> #define XTAL            11059200UL
> #define BAUD         115200UL
>
> #define OffLED()        PORTD |= _BV(PD3)    // status LED control
> #define OnLED()         PORTD &= ~_BV(PD3)
>
> #define RX_BUF_LEN      8
> #define TX_BUF_LEN      8
>
>                 /*----- Function Prototypes -----*/
>
> void     delay_ms(ui msec);
> int   com_getchar(void);
> int      com_putchar(char c);
> void     UpdateSR(void);
>
>                 /*----- Global Variables -----*/
>
> static   uc   cRxBuf[RX_BUF_LEN];     // uart rx-isr var
> static   uc   cRxWrNdx, cRxRdNdx;
> volatile uc   cRxCtr;
>
> static   uc   cTxBuf[TX_BUF_LEN];     // uart tx-isr var
> static   uc   cTxWrNdx, cTxRdNdx;
> volatile uc   cTxCtr;
>
> uc            cRxData;
>
> /*--------------------------------*/
> int     main(void)
> {
>  DDRA  = 0xFF;     // 1-output, 0-input
>  DDRB  = 0xFF;
>  DDRC  = 0xFF;
>  DDRD  = 0xFE;
>  PORTD = 0xFF;
>
>  UBRRH = 0x00;     // baudrate 115200
>  UBRRL = 0x05;      // (XTAL/(16 * BAUD)) - 1
>  UCSRB = 0xD8;     // Rx-Tx On, Rx-Tx inter. enable
>  UCSRC = 0x86;     // 8 data bits, no parity, 1 stop bit
>
>  ACSR  = 0x80;     // comparator off
>  sei();             // enable interrupts
>
>  OnLED();
>  delay_ms(250);
>  OffLED();
>
>  fdevopen(com_putchar, com_getchar, 0);
>  puts_P(PSTR("Hello from MEGA8535\n\r"));
>
>  for (;;)
>   {
>    cRxData = com_getchar();
>
>    if (cRxData == '1')
>      OnLED();
>    else
>      OffLED();
>
>    com_putchar(cRxData);
>   }
> }
> /*--------------------------------*/
> void    delay_ms(ui msec)
> {
>  while (msec)
>   {
>    --msec;
>    _delay_loop_2((ui)(XTAL / 4000));   // delay 1 msec
>   }
> }
> /*--------------------------------*/
> int     com_getchar(void)
> {
>  ui  c;
>
>  while (cRxCtr == 0);   // wait for char
>  c = cRxBuf[cRxRdNdx++];
>
>  if (cRxRdNdx >= RX_BUF_LEN)
>    cRxRdNdx = 0;
>
>  cli();
>  cRxCtr--;
>  sei();
>  return(c);
> }
> /*--------------------------------*/
> int     com_putchar(char c)
> {
>  while (cTxCtr >= TX_BUF_LEN);
>
>  if ((cTxCtr == 0) && (bit_is_clear(UCSRA, UDRE)))
>    UDR = c;
>  else
>    {
>     cTxRdNdx++;
>
>     if (cTxRdNdx >= TX_BUF_LEN)
>       cTxRdNdx = 0;
>
>     cTxBuf[cTxRdNdx] = c;
>     cli();
>     cTxCtr++;
>     sei();
>    }
>
>  return(0);
> }
> /*--------------------------------*/
> SIGNAL (SIG_UART_RECV)
> {
>  cRxBuf[cRxWrNdx++] = UDR;
>
>  if (cRxWrNdx >= RX_BUF_LEN)
>    cRxWrNdx = 0;
>
>  if (cRxCtr++ >= (RX_BUF_LEN + 1))
>    cRxCtr = RX_BUF_LEN;
> }
> /*--------------------------------*/
> SIGNAL (SIG_UART_DATA)
> {
>  if (cTxCtr != 0)
>    {
>     cTxCtr--;
>     cTxWrNdx++;
>
>     if (cTxWrNdx > TX_BUF_LEN)
>       cTxWrNdx = 0;
>
>     UDR = cTxBuf[cTxWrNdx];
>    }
> }
>
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