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.
