• Locked Locked
  • Replies 10 replies
  • Subscribers 120 subscribers
  • Views 9876 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Output data via SWO without debugger ?

Martin Maurer
Note: This was originally posted on 15th November 2010 at http://forums.arm.com

Hello,

i am using a Cortex-M3 (in my case a TI Stellaris LM3S9B92 Rev B1).
I would like to know, if it is possible to output data via SWO without a debugger ?
Do i need any clocks (via SWD) from outside (normally generated by the debugger) to output data via SWO (UART, not Manchester) ?

I already tried the following from inside Cortex-M3:

In setup:

#define TRCENA       0x01000000

#define DEMCR     (*((volatile unsigned long *)(0xE000EDFC)))
#define TRACE_ENABLE_REGISTER     (*((volatile unsigned long *)(0xE0000E00)))
#define TRACE_CONTROL_REGISTER       (*((volatile unsigned long *)(0xE0000E80)))
#define ASYNC_CLOCK_PRESCALER_REGISTER  (*((volatile unsigned long *)(0xE0040010)))
#define SELECTED_PIN_CONTROL_REGISTER   (*((volatile unsigned long *)(0xE00400F0)))

             DEMCR = DEMCR | TRCENA;

             TRACE_ENABLE_REGISTER = 0xFFFFFFFF;

             TRACE_CONTROL_REGISTER = 0x00000001;

             ASYNC_CLOCK_PRESCALER_REGISTER = 10;

             SELECTED_PIN_CONTROL_REGISTER = 0x00000002;

In main loop:

   if (DEMCR & TRCENA)
   {
     while (ITM_Port32(0) == 0);
     ITM_Port8(0) = 0x41;
   }


But i don't see any activity on SWO, nor is the line switched to output at all...

Best regards,

Martin
Parents
  • Note: This was originally posted on 15th November 2010 at http://forums.arm.com

    Hello Joseph,

    many thanks for your answer !


    The ITM has a lock register that you need to unlock before programming the ITM.
    After setting TRCENA, could you add
    #define ITM_LOCK_ACCESS_REGISTER  (*((volatile unsigned long *)(0xE0000FB0)))
    ITM_LOCK_ACCESS_REGISTER = 0xC5ACCE55;


    Unfortunately it is still not working. Is there perhaps some switch to enable SWJ, disable JTAG ?
    The pin where SWO is on behaves still like an input.
    Is there some clock on TCLK needed for at leats part of the functionality ?

    Best regards,

    Martin
Reply
  • Note: This was originally posted on 15th November 2010 at http://forums.arm.com

    Hello Joseph,

    many thanks for your answer !


    The ITM has a lock register that you need to unlock before programming the ITM.
    After setting TRCENA, could you add
    #define ITM_LOCK_ACCESS_REGISTER  (*((volatile unsigned long *)(0xE0000FB0)))
    ITM_LOCK_ACCESS_REGISTER = 0xC5ACCE55;


    Unfortunately it is still not working. Is there perhaps some switch to enable SWJ, disable JTAG ?
    The pin where SWO is on behaves still like an input.
    Is there some clock on TCLK needed for at leats part of the functionality ?

    Best regards,

    Martin
Children
No data