How to use printf in CodeWarrior v5.x/MC9S12(X)

How to use standard input and output in CodeWarrior v5.x/MC9S12(X)

It is not possible to use standard input and output directly under CodeWarrior. The reason is probably very simple. The microcontroller does not have a console, and different microcontrollers have different ports. How does the compiler know where to printf, getchar, putchar...

To solve this problem, the standard input and output in the standard library implementation provided by CodeWarrior actually call the two functions TERMIO_GetChar and TERMIO_PutChar respectively. These two functions require users to implement them. The function prototypes are as follows:

// Receive a character from the terminal channel

// Return: characters received from the terminal channel

char TERMIO_GetChar(void);  

// Send a character to the terminal channel

// Parameter: ch character to be sent to the terminal channel

void TERMIO_PutChar(char ch);

So in order to use the functions that we had fun using when learning C language, we have to implement these two functions ourselves as needed.

The example uses the SCI module I wrote myself and uses SCI0 as the terminal channel:

#include       /* common defines and macros */

#include "derivative.h"      /* derivative-specific definitions */

#include

#include "SCI_def.h"

void TERMIO_PutChar(char ch){

  SCI_PutChar(SCI0,(unsigned char)ch);

}

char TERMIO_GetChar(void){

  return SCI_GetChar(SCI0);

}

void main(void) {

  int c;

  // Enable SCI0

  SCI_Init(SCI0);

  SCI_EnableTrans(SCI0);

  SCI_EnableRecv(SCI0);

  printf("type something:r");

  for(;;) {

    // Receive characters and echo them

    c = getchar();

    putchar(c);

  }

}

The reason why SCI0 is used is because the terminal window in the simulation uses SCI0, which is more convenient for demonstration hhh

ps: Actually, I didn't use standard input and output when programming embedded systems, but some libraries use standard output by default, so I did some research.