Showing results for 
Search instead for 
Did you mean: 

Unable to program STM32WB5MMG on custom board


I have recently taken delviery of a custom board carring the SMT32WB5MMG SiP. This is the first time I have used this specific part in a custom design, but previously have been working with a SMT32WB55 development kit without any issues.

In my design I have followed the guidelines in the datasheet to the best of my ability, supplying power to the SiP as shown in the reference schematics provided on page 14.

I am trying to program the board via a SWD header (supplying 3V3 power to this header only), but have had difficulty connecting to the board with any combinaton of settings in STM32CubeProgrammer;


The reference doesn't explicitly show how the SWD pins should be connected, but I assume a direct connection to the SWDIO and SWCLK pins would be sufficient. Please see my schematic for the controller below;


Can someone please review my schematic and provide some advice on what might be going wrong here?

Many thanks,


ST Employee

Hello Craig,
Checking your system pins assignment (power, reset, SWD) I don't see any problem which shall prevent connection to the MCU. Yes, direct connection from J2 pin header to STlink is expected
Few questions/ setting recommendation:
- what is your your BOOT0 connection? Do you leave it floating or connect to some logic level?
- what ST link do you use? Some standalone probe, or some other nucleo board with SWD interface?

- in STM32CubeProgrammer please make sure you use Mode "Under reset", Reset Mode "Hardware reset" and for test please try to decrease Frequency (can be problematic for longer wires from STlink to target)
- Can you measure your VDD level and stability and nRST shape? Instability here could cause the issue as well, but not expected.
- Do you observe issue with multiple custom boards with module, or just one? In case you have issue only with some samples, soldering verification could help as well.

Best regards,