LoRa communication not working in STM32WL55CCU6 with 32 MHz crystal

[NOza.2]

Hello STM32WL Expert,

We have developed a custom PCB based on the "STM32WL_QFN48_4Layers_Ref_Board" reference design with STM32WL55CCU6 MCU. It is based on high power and high-frequency configuration. LoRa transmission is handled through the FE_CTRL_2 pin for data transmission and receiving.

We are using 32MHz crystal at OSC_IN and OSC_OUT pins. As per reference manual (RM0453) point 5.4.2, the load capacitors are provided by the integrated

capacitor banks that can be trimmed. The trimming is provided by SUBGHZ_HSEINTRIMR and SUBGHZ_HSEOUTRIMR registers.

SUBGRF_WriteRegister( REG_XTA_TRIM, XTAL_DEFAULT_CAP_VALUE);
SUBGRF_WriteRegister( REG_XTB_TRIM, XTAL_DEFAULT_CAP_VALUE);

We have developed the same application on the NUCLEO-WL55JC1 development board and it is working well. The same LoRa communication is not working with custom PCB. Will you please help us to debug the issue?

Best Regards,

Neel

[IIRHO.1]

Hello @NOza.2 and welcome to ST Community.

I suggest you to take a look on the parts 2.2.8 and 2.2.18 Errata sheet of the STM32WL55CCU6 that can help you.

When your question is answered, please close this topic by choosing "Accept as Solution". This will help other users find that answer faster.

Issam

[NOza.2 · Accepted solution]

Hello @IIRHO.1 ,

Thank you for your suggestion. This issue was related to value of "XTAL_DEFAULT_CAP_VALUE". Once we change the value to zero, it worked well.

Regards,

Neel