9 Replies Latest reply on Feb 24, 2020 2:02 AM by user_2738496

    PSOC6 Serial Wire Viewer


      Hi, I am searching for information on how to get printf working over the SWD port.

      I have a miniprog3 connected and I would like a terminal on my computer where I can see debug messages.


      Does anyone have some code to set this up? (I guess more is needed than selecting "SWD+SWV" in Programming/Debugging)


      Also what is the best way to watch the output? Is it getting a J-link, looking in the Output tab of PSOC Creator, or something else?


      So far I have borrowed this together off the internet,


      best regards





      *       Defines for Cortex-M debug unit


      #define ITM_STIM_U32 (*(volatile unsigned int*)0xE0000000)    // Stimulus Port Register word access

      #define ITM_STIM_U8  (*(volatile         char*)0xE0000000)    // Stimulus Port Register byte access

      #define ITM_ENA      (*(volatile unsigned int*)0xE0000E00)    // Trace Enable Ports Register

      #define ITM_TCR      (*(volatile unsigned int*)0xE0000E80)    // Trace control register




      *       SWO_PrintChar()


      * Function description

      *   Checks if SWO is set up. If it is not, return,

      *    to avoid program hangs if no debugger is connected.

      *   If it is set up, print a character to the ITM_STIM register

      *    in order to provide data for SWO.

      * Parameters

      *   c:    The Chacracter to be printed.

      * Notes

      *   Additional checks for device specific registers can be added.


      void SWO_PrintChar(char c) {


        // Check if ITM_TCR.ITMENA is set


        if ((ITM_TCR & 1) == 0) {




        // Check if stimulus port is enabled


        if ((ITM_ENA & 1) == 0) {




        // Wait until STIMx is ready,

        // then send data


        while ((ITM_STIM_U8 & 1) == 0);

        ITM_STIM_U8 = c;




      int _write(int file, char *ptr, int len)


          int i;


          for (i = 0; i < len; i++)




          return len;


        • 1. Re: PSOC6 Serial Wire Viewer

          You can always use an UART component in your firmware to sent out debugging messages. PSoC 6 kit has an embedded USB to UART, so you can use PC Terminal to visualize debug messages sent by your firmware.

          • 2. Re: PSOC6 Serial Wire Viewer

            Yes, I know, but I think the debug port is generally the most elegant way to do it, and in the long run I want the code to run on boards lacking the kitprog2

            • 3. Re: PSOC6 Serial Wire Viewer

              I found and added some initiation code also, but it get what seems to be a bus fault when accessing the TPI unit,
              anyone know why?


              CoreDebug->DEMCR |= (1 << 24);

              ITM->LAR  = 0xC5ACCE55;

              ITM->TER  = 0x0;

              ITM->TCR  = 0x0;

              TPI->SPPR = 2;

              TPI->ACPR = 24;

              ITM->TPR  = 0x0;

              DWT->CTRL = 0x400003FE;

              ITM->TCR  = 0x0001000D;

              TPI->FFCR = 0x00000100;

              ITM->TER  = 0x1;

              • 4. Re: PSOC6 Serial Wire Viewer

                If you check core_cm4.h file, there are three system call functions:

                - ITM_SendChar

                - ITM_ReceiveChar

                - ITM_CheckChar


                They use the ITM channel to send/receive messages.

                • 5. Re: PSOC6 Serial Wire Viewer

                  How can one listen to the data send on the ITM channel?

                  • 6. Re: PSOC6 Serial Wire Viewer

                    Thanks, I checked, and the ITM_SendChar i virtually identical to the SWO_Printchar function.


                    I tried running:

                    GitHub - kyoung2112/csharp-miniprog3-swv: C# Express SWV Printf viewer for Miniprog3


                    And also J-link + SWO-viewer.


                    Checking using a logic analyzer I see that nothing happens on the SWO pin.


                    If this is at all possible something more is needed.

                    • 7. Re: PSOC6 Serial Wire Viewer

                      To read the debug printf messages through SWV pin, I did the following:


                      1. Changed the Debug Select to SWD+SWV in one of the PSoC 6 MCU project and built it.

                      2. Exported the project to Keil uVision 5 by following the steps provided in Creating µVision Projects for PSoC 6 of the PSoC Creator Help document.

                      3. Redirected the STDERR, STDIN, STDOUT to ITM in Keil uVision IDE's is Run-time Environment (steps are available in the uVision's User Guide).

                      4. Connected the ULINKpro debugger to J11 header CY8CKIT-062-BLE board. Rebuilt the project in uVision and started the debug session.

                      I was successfully able to see the message steam in Debug (printf) Viewer window of the uVision IDE.


                      Although I haven't used the MiniProg3 here, thought of sharing this info, if you are interested to try.

                      1 of 1 people found this helpful
                      • 8. Re: PSOC6 Serial Wire Viewer

                        Did you manage to use the SWO pin? A have the same issue with a Psoc6. No activity on SWO pin.


                        I configure and enable the ITM using the code below


                        // Debug Exception Monitor and Control register

                        #define DEMCR   (*((unsigned long *) 0xe000edfc))

                        #define TRCENA  0x01000000  // enable trace

                        // Stimulus Port registers

                        #define ITM_STIM0 (*((unsigned long *) 0xe0000000))

                        #define ITM_STIM1 (*((unsigned long *) 0xe0000004))

                        #define ITM_STIM2 (*((unsigned long *) 0xe0000008))

                        #define ITM_STIM3 (*((unsigned long *) 0xe000000c))

                        // Trace enable registers

                        #define ITM_TER   (*((unsigned long *) 0xe0000e00))

                        // Privilege register: registers that can be accessed by unprivileged code

                        #define ITM_TPR   (*((unsigned long *) 0xe0000e40))

                        // Trace Control register

                        #define ITM_TCR   (*((unsigned long *) 0xe0000e80))

                        // Lock Access register

                        #define ITM_LAR   (*((unsigned long *) 0xe0000fb0))

                        // unlock value

                        #define ITM_LAR_ACCESS  0xc5acce55


                        void ITM_init(void)


                            ITM_LAR = ITM_LAR_ACCESS; // unlock

                            ITM_TCR = 0x1;            // global enable for ITM

                            ITM_TPR = 0x1;            // first 8 stim registers have unpriv access

                            ITM_TER = 0xf;            // enable 4 stim ports

                            DEMCR = TRCENA;           // global enable DWT and ITM





                        and the implimation of fputc()




                        int32_t ITM_SendChar (int32_t ch) {

                          if ((ITM_TCR & ITM_TCR_ITMENA_Msk) && /* ITM enabled */

                              (ITM_TER & (1UL << 0)        )) { /* ITM Port #0 enabled */

                            while (ITM_PORT0_U32 == 0);

                            ITM_PORT0_U8 = (uint8_t)ch;


                          return (ch);



                        The ITM_PORT0_U32 is always 0 so never return from the while (ITM_PORT0_U32 == 0);

                        • 9. Re: PSOC6 Serial Wire Viewer

                          No, I never tried the Keil solution as we were not going to be using Keil anyway, so I gave up.