STM32WB55 Custom board programming issue

[Stm325]

Hello,

I have designed a custom board with stm32wb55. I used the reference schematic and checked everything but I cannot program the board from my cubeide. I have tried different configuration settings in Cube IDE but always got "No device on target" error. I connecte SWDIO, SWCLK, GND and NRST pin to my stlink. These did not work so I tried different configurations with OpenOCD too but they also failed with these symptoms

Symptoms (Multiple attempts with OpenOCD at 100 kHz):

• SWD-DP responds reliably: chip identified as Cortex-M4 r0p1
• Examination usually succeeds: shows correct breakpoint and watchpoint counts
• Halt always fails with "Fail reading CTRL/STAT register" → "Not halted"
• Roughly 1 in 4 attempts fail to even initialize, but when init succeeds, halt always fails
• Manual NRST-to-GND-then-release tried, same result
• Already reflowed the WB55 once with gel flux, no change in behavior

Tried:

• Multiple OpenOCD reset modes including connect-under-reset
• Speeds from 480 kHz down to 100 kHz
• Forcing a halt by directly writing to the Cortex-M4 debug control register
• A flash option-byte regression sequence to rule out readout protection (RDP)

I measured that VDD is 3.3V, NRST is 3.3V, SWDIO is 3.3V and SWCLK is 0.

I also tried programming with NRST connected the ground and then pulled while programming etc.

Nothing really worked out. This is my schematic design. I appreciate any recommendation.

[Imen.D]

Hello @Stm325 ,

First, check connectors and USB cable. Ensure also that your board is properly powered and connected.

Is your STM32WB55 custom board detected by STM32CubeProgrammer?

If it connects to the target, erase the flash, program a new application, erase again, disconnect, and retry debugging.

Refer to these FAQs that may be helpful for you:

• How to solve connection errors when connecting and programming the STM32 target board.
• How to solve debugger connection issue

[Stm325]

It is not detected by cubeprogrammer. And when I connect ST-Link(From my nucleo-64 board), system current draw increase around 80 mA. I have checked how to direct st-link of Nucleo to external board. With 140kHz frequency I get "Target Unknown Error 19" and with other frequencies it just says "Target device not found", I am trying to understand if I did something wrong in my schematics but I cannot see anything that will prevent me from programming the chip. I have checked the power pins etc and they are at 3.3V too

[Imen.D]

Ensure your ST-LINK firmware is up to date. 

Otherwise, this could be caused by a misconfiguration of the communication pins between the board and the ST-Link.

The problem also might be with the ST-Link. Make sure that you use a genuine ST-LINK/V2: How to recognize a genuine ST-LINK/V2 versus a cloned one.