SWO stops collecting data after a few packets

[Herm]

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 

[AScha.3]

Maybe the buffer (in IDE) is full.  But it should give you a message about this.

Try : making bigger ;  in window -> preferences -> 

[Pavel A.]

Please try using the CubeProgrammer (GUI or CLI), it has SWO output mode.

[Herm]

Thank you for your suggestion. I increased it tenfold but the effect is the same. After ~2500 packets the trace stops.

[Herm]

Cube Programmer doesn't seem to have an option for data trace, but that's the function I need. 

[Pavel A.]

[andershedberg]

I have the same problem. I need to restart the debugging session for it to get going again. Any updates on this? It's useless right now.
---
Pavel A's suggestion of using the Serial Wire Viewer in the STM32CubeProgrammer do work(!) and I can see both the characters nad the printf data numbe increase. Very strange, but it seems the STM32Cube has some errors regarding SWO output.

[tjaekel]

SWO viewer works fine for me since years.

When it could fails (after number of packets) - my guesses:

• your code (FW) crashes
• you reconfigure the system clock (a different core clock now)
• maybe: you send too often (and too fast, in terms of repetitions - the SWO goes via "slow" speed debug infrastructure and via single serial wire, you "overflow" the DAP, debug)
• something in your code disables the SWO (inside MCU)
• you use the SWO pin for something else (e.g. a GPIO or a peripheral device signal)
• you slow down the MCU (clock config) or you change the voltage range (entering low power mode)

[andershedberg]

There are several problems. I use the ST-Link V3Mini-e, and if I use the USB on the back of the computer, it simply stops after ~1000 frames. If I use the USB ports on the front, it just continues to stream. This is on Debian and the STM32CubeProgrammer. This is when i use a small STM32 controller.

There are also known issues with the STM32H723/33 that I am using and getting SWO to work. Several threads on this forum about it... I've now ordered a plain disco board and a Segger debugger that uses ethernet intstead of USB to see if this sorts out some of the strange things. 

[Pavel A.]

>  if I use the USB on the back of the computer, it simply stops after ~1000 frames. If I use the USB ports on the front, it just continues to stream.

🤔