STM32WL55 no rf

[SDu T]

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)

VLXSMPS = 1.5V,

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

[bmckenney · Accepted solution]

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).

[SDu T]

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