Debug (printf) Viewer

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Debug (printf) Viewer

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The Debug (printf) Viewer window displays data streams that are transmitted sequentially through the ITM Stimulus Port0. Enable ITM Stimulus Port 0.

To use the viewer for trace output:

1. Add ITM Stimulus Port register definitions to the 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 a fputc function which writes to the ITM Stimulus Port 0 register to the source code, which allows using printf for debug output.

   struct __FILE { int handle; /* Add whatever needed */ };
   FILE __stdout;
   FILE __stdin;
   
   int fputc(int ch, FILE *f) {
     if (DEMCR & TRCENA) {
       while (ITM_Port32(0) == 0);
       ITM_Port8(0) = ch;
     }
     return(ch);
   }
   

3. Add the debug trace messages.

   printf("AD value = 0x%04X\r\n", AD_value);
   

4. Set ITM Stimulus Port Port 0 bit to allow Trace to capture the ITM Port 0 information. Clear the Port 7..0 privilege bit to allow access to the Port 0 bit from User mode.
   
   
5. Select View - Serial Windows - Debug (printf) Viewer to launch the window.
   
   

 Note

• Only data transmitted over ITM Stimulus port 0 is displayed in the Debug (printf) Viewer window. Other ITM Ports can be monitored with the Trace Records Window.