Problem trying to implement a putchar function

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Abner Barros

• June 02, 2022 20:48

I need to implement my version of putchar function to work with MSP430 UART ISR.

The problem is that if I try to create the function __putchar(int c) the compiler show error with "redeclaration of '__putchar'..." and if I try to creat _putchar(int c) it said "undefined symbol '___putchar'" when I use printf function.

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  Dr Danish Ali

  • June 05, 2022 11:57

  Be careful that there are two underscores at the start of the name __putchar()

  Another point is that __putchar should return an int, so in a header file that you use the prototype would be:

  int __putchar(int c);

  Then in ONE .c file that you link into your project, have the definition

  int __putchar(int c) {
      /* whatever you need to do to send the character c to the MSP430 uart */
      return c;
  }

   

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