newlib printf function bug

Question

I am trying to send printf data to my uart device. I have suitablely written write_r() funciton.

The problems that I am having is,

• When I say printf(" My name is sam \n I am fine ");
• and in next time when i say printf(" I am back ");

1st problem : I can see only "My name is Sam", then the cursor goes to next line and stops there.

2nd problem : "I am back" is not getting printed at all.

I tried by removing \n , still the 2nd printf doesn't get printed. There is nothing wrong with the uart.

Looks like then \ is reached the pointer is lost.

My Code

    int write(int file, char *ptr, int len) {

            #if !defined( OUT_8 )
        #define OUT_8(p,d)      (*(volatile char *)(p) = (char)(d))
        #endif
        #if !defined( IN_8 )
            #define IN_8(p)         ((*(volatile char *)(p)))
        #endif

        OUT_8(DUART1_UMCR1, 0x02); //Informs external modem or peripheral that the UART is ready for sending data
        OUT_8(DUART1_ULCR1, 0x03);
        OUT_8(DUART1_UIER1, 0x0f);
        OUT_8(DUART1_UFCR1, 0x8f);

        OUT_8(DUART1_UTHR, '\n');
        OUT_8(DUART1_UTHR, '\r');
        while (ptr!=NULL)
        {
            if (*ptr=='\n') // JUST A TRY to avoid \n bug
            {
             OUT_8(DUART1_UTHR, '\n');
             wait();
             *ptr++;
             *ptr++;
             OUT_8(DUART1_UTHR, *ptr++); // \n & \r when given through printf isNot working
             wait();
            }


            OUT_8(DUART1_UTHR, *ptr++); // \n & \r when given through printf is not working 
            wait(); // TODO:

            if(len==0)
                break;
            else
                len--;
        }

            OUT_8(DUART1_UMCR1, 0x00); // say that modem is not not ready. Connection over
            OUT_8(DUART1_UFCR1, 0x87);
            OUT_8(DUART1_ULCR1, 0x00); // Clear all the interrupts ! virtually shut the UART port
    errno = ENOSYS;
    return -1;
}

Answer 1

Confident that OP's I/O is buffered somewhere.
Output does not appear until a \r and/or \n is sent.

#if !defined( OUT_8 )
  #define OUT_8(p,d)      (*(volatile char *)(p) = (char)(d))
#endif

// make ptr a `const char *`
int write(int file, const char *ptr, int len) {
  OUT_8(DUART1_UMCR1, 0x02); //Informs UART is ready for sending data
  OUT_8(DUART1_ULCR1, 0x03);
  OUT_8(DUART1_UIER1, 0x0f);
  OUT_8(DUART1_UFCR1, 0x8f);

  while (len-- > 0) {
    OUT_8(DUART1_UTHR, *ptr++);
    wait();
  }

  // Force an EOL at the _end_ of transmission.
  OUT_8(DUART1_UTHR, '\n');
  OUT_8(DUART1_UTHR, '\r');
  wait();

  OUT_8(DUART1_UMCR1, 0x00); // say that modem is not not ready. Connection over
  OUT_8(DUART1_UFCR1, 0x87);
  OUT_8(DUART1_ULCR1, 0x00); // Clear all interrupts! virtually shut UART port
  errno = ENOSYS;
  return -1;
}

---

I suspect that the buffering is occurring in the receiving side, either the UART or more likely in the terminal viewing the data. OP said "the curser goes to next line". There is no "cursor" in a UART.

Answer 2

Try calling fflush() to force printing without a \n.