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Using ST-LINK_gdbserver with STM32H7 without hardware reset

JojoS
Associate III

I'm using VSCode/Debug-Cortex with STLink V3Mini. The target is a board with STM32H743VI and SWD. The board has only basic swd with GND, 3V3, SWDIO, SWCLK. There is no reset line, unfortunately also not on other headers.

When I start debugging, the debug probe connects and loads some stub to flash. After that, it tries to reset again, but this fails. It works only when I solder connect a reset line and cube programmer can perform a connect under reset.

STMicroelectronics ST-LINK GDB server. Version 5.8.0
Copyright (c) 2020, STMicroelectronics. All rights reserved.
 
Starting server with the following options:
        Persistent Mode            : Disabled
        Logging Level              : 31
        Listen Port Number         : 50000
        Status Refresh Delay       : 15s
        Verbose Mode               : Disabled
        SWD Debug                  : Enabled
 
Target connection mode: Default
Reading ROM table for AP 0 @0xe00fefd0
Hardware watchpoint supported by the target 
COM frequency = 24000 kHz
ST-LINK Firmware version : V3J7M2
Device ID: 0x450
PC: 0x80037fc
ST-LINK device status: HALT_MODE
ST-LINK detects target voltage = 3.29 V
ST-LINK device status: HALT_MODE
ST-LINK device initialization OK
Waiting for debugger connection...
Waiting for connection on port 50000...
Accepted connection on port 50000...
Debugger connected
Enter STM32_AppReset() function 
NVIC_DFSR_REG = 0x0000000B
NVIC_CFGFSR_REG = 0x00000000
 ------ Switching to STM32CubeProgrammer ----- 
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.8.0                  
      -------------------------------------------------------------------
 
ST-LINK SN  : 004900313137510B33333639
ST-LINK FW  : V3J7M2
Board       : STLINK-V3MINI
Voltage     : 3.29V
SWD freq    : 24000 KHz
Connect mode: Under Reset
Reset mode  : Hardware reset
Device ID   : 0x450
Revision ID : Rev V
Device name : STM32H7xx
Flash size  : 2 MBytes
Device type : MCU
Device CPU  : Cortex-M7
BL Version  : 0x90
 
 
 
Memory Programming ...
Opening and parsing file: ST-LINK_GDB_server_a16228.srec
  File          : ST-LINK_GDB_server_a16228.srec
  Size          : 40704 Bytes
  Address       : 0x08000000 
 
 
Erasing memory corresponding to segment 0:
Erasing internal memory sector 0
Download in Progress:
 
 
File download complete
Time elapsed during download operation: 00:00:00.988
 ------ Switching context ----- 
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
Target no device found

is it possible to connect also in normal mode, without reset line?

2 REPLIES 2
Uwe Bonnes
Principal III

For an off board connection, try to lower "COM frequency = 24000 kHz" or provide substantial more ground connections.

JojoS
Associate III

thanks Uwe,

flashing and debugging works reliable, its only the reset line. When I tried the connection in the command line, I could see also that STM32CubeProgrammer tries to connect with lower speed by itself.

The problem is almost cosmetic, the extra wire is not looking nice. And its for my curiosity.