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Debug (printf) Viewer

The Debug (printf) Viewer window displays data streams that are transmitted sequentially through the ITM Stimulus Port 0. Enable ITM Stimulus Port 0.

Debug Viewer Window

To use the Debug (printf) Viewer for tracing:

  1. Add ITM Port register definitions to your source code.
    #define ITM_Port8(n)    (*((volatile unsigned char *)(0xE0000000+4*n)))
    #define ITM_Port16(n)   (*((volatile unsigned short*)(0xE0000000+4*n)))
    #define ITM_Port32(n)   (*((volatile unsigned long *)(0xE0000000+4*n)))
    #define DEMCR           (*((volatile unsigned long *)(0xE000EDFC)))
    #define TRCENA          0x01000000
  2. Add an fputc function to your source code that writes to the ITM Port 0 register. The fputc function enables printf to output messages.
    struct __FILE { int handle; /* Add whatever you need here */ };
    FILE __stdout;
    FILE __stdin;
    int fputc(int ch, FILE *f) {
      if (DEMCR & TRCENA) {
        while (ITM_Port32(0) == 0);
        ITM_Port8(0) = ch;
  3. Add your debugging trace messages to your source code using printf.
    printf("AD value = 0x%04X\r\n", AD_value);
  4. Set the ITM Port 0 to capture the information. Clear the Port 7..0 privilege bit to access ITM Port 0 from User mode.

    ITM Stimulus Port 0

  5. Open the View - Serial Windows - Debug (printf) Viewer window.


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