Hello everyone,
I am working with a custom board based on STM32WB55CGU6. The MCU is brand new and no firmware has ever been programmed into the device.
The reset circuit and BOOT0 circuit are shown in Figure 1.
Problem:
I cannot connect to the MCU using STM32CubeProgrammer through SWD.
Connection settings:
Port: SWD
Mode: Under Reset
Reset Mode: Hardware Reset
Frequency: 4 MHz (also tested with lower frequencies)
STM32CubeProgrammer reports:
"No STM32 target found"
and sometimes:
"Unable to get core ID"
A screenshot of the error is shown in Figure 2.
Troubleshooting already performed:
Verified continuity of the SWD signals:
PA13 (SWDIO) to ST-LINK SWDIO
PA14 (SWCLK) to ST-LINK SWCLK
Power supply appears normal:
Target voltage reported by STM32CubeProgrammer is approximately 3.25 V
Power rails have been checked
Measured voltage:
Voltage measured directly between SWCLK and SWDIO is approximately 3.267 V
BOOT0 is pulled down to GND through a 10 kΩ resistor.
NRST is pulled up to 3.3 V through a 10 kΩ resistor and connected to the ST-LINK reset pin.
SWDIO and SWCLK each measure approximately 11.2 MΩ to GND, indicating no obvious short circuit.
STM32CubeProgrammer was tested using Under Reset mode.
Questions:
Is there anything specific to STM32WB55 that could prevent the debugger from reading the Core ID?
Are there any mandatory power pins, such as VDDA, VDDRF, VDDSMPS, or VBAT, that could cause this behavior if improperly connected?
Has anyone encountered a similar issue on a brand-new STM32WB55 device?
Any suggestions would be greatly appreciated.
Thank you.
Figure 1: Schematic of NRST and BOOT0 circuits
Figure 2: STM32CubeProgrammer error screenshot
