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STM32WL55 no rf

Associate III

Good day

I am using the STM32WL55 chip for a project. I did preliminary tests using the NUCLEO-WL55JC2 Development board.

I created a custom PCB following the design of the Development board.

When I program the custom board with the same firmware that works on the development kit I do not get any output on either the RFO_HP pin or the RFO_LP pin.

On the Custom board I have a crystal and not a TXCO. Can that configuration have a impact?

On the Custom board:

VDDRF = 3.3V, VDDPA = 3.3V ( I need the high power output)


Is there someone that can suggest  checks to do  to find the fault?




If you're using a crystal rather than a TCXO, you need to adjust the BSP_RADIO_IsTCXO function in stm32wlxx_nucleo_radio.c. 

Also, for a crystal, radio_driver.c (SUBGRF_Init) loads the HSE trim capacitors with XTAL_DEFAULT_CAP_VALUE; if you haven't changed this, it will be 0x20. I've forgotten what the units are, but it turns out that this is very large -- enough to throw the oscillator timing off. We had designed-in external capacitors, so we used 0x00 instead. You may want something larger (0x08, maybe?). You can monitor the HSE32 via the MCO (PA8).

Associate III

Good day


Thank you for the response.

I have decided to use the TCXO as it will give me  much better reliability out in the field with temperature changes