SWO stops collecting data after a few packets

Herm · ‎2024-01-15

I'm trying to do some debugging using SWO on an STM32G474. After a very short amount of time no new packets are displayed in CubeIDE (usually after ~2500 packets). I limited the SWO frequency to various values between 100kHz and 8 MHz. Using an oscilloscope I can verify that the data is still being output at the correct rate by the MCU but no data is received by either the STLink probe or CubeIDE.

I tried many combinations of settings (shared STLink, OpenOCD instead of ST-Link GDB server, reset mode, low power debug mode [I don't use low power modes], baudrate, etc.) and nothing worked.

CubeIDE version 1.14.0.

Debug log:


STMicroelectronics ST-LINK GDB server. Version 7.5.0
Copyright (c) 2023, STMicroelectronics. All rights reserved.

Starting server with the following options:
        Persistent Mode            : Disabled
        Logging Level              : 1
        Listen Port Number         : 61234
        Status Refresh Delay       : 15s
        Verbose Mode               : Disabled
        SWD Debug                  : Enabled

Waiting for debugger connection...
Debugger connected
Waiting for debugger connection...
Debugger connected
Waiting for debugger connection...
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.15.0                  
      -------------------------------------------------------------------



Log output file:   C:\Users\HERMAN~1\AppData\Local\Temp\STM32CubeProgrammer_a30704.log
ST-Link Server is running on port : 7184
ST-LINK SN  : 001E001A3756501220303658
ST-LINK FW  : V3J13M4B5S1
Board       : STLINK-V3MODS
Voltage     : 3.26V
SWD freq    : 8000 KHz
Connect mode: Under Reset
Reset mode  : Hardware reset
Device ID   : 0x469
Revision ID : Rev Y
Device name : STM32G47x/G48x
Flash size  : 512 KBytes
Device type : MCU
Device CPU  : Cortex-M4
BL Version  : 0xD4
Debug in Low Power mode enabled



Memory Programming ...
Opening and parsing file: ST-LINK_GDB_server_a30704.srec
  File          : ST-LINK_GDB_server_a30704.srec
  Size          : 123.54 KB 
  Address       : 0x08008000 


Erasing memory corresponding to segment 0:
Erasing internal memory sectors [8 38]
Download in Progress:


File download complete
Time elapsed during download operation: 00:00:02.383



Verifying ...




Download verified successfully

Herm · ‎2024-02-22

Sorry for my late reply. I had to work on other projects for some time.

As far as I can see this function is only for printf-style debugging. I need data trace debugging where I record every change of a certain memory location without modifying my code.

Herm · ‎2024-02-22

Thank you for your suggestions. However I am pretty sure none of these apply as I can still see the SWO stream at the right baud rate using my oscilloscope.

Pavel A. · ‎2024-02-22

> As far as I can see this function is only for printf-style debugging

> I need data trace debugging where I record every change of a certain memory location

ITM_PrintChar is the "API" usually intended for printf. But ITM (the thing behind the SWO line) can do much more than a simple printf. Look at the ITM configuration dialog and read some ARM documentation to get a clue. Yes, it can be used for data watchpoints.

Herm · ‎2024-03-21

Today I upgraded to STM32CubeIDE 1.15.0 and performed the STLink upgrade that came with it. Now SWO works again.