Hi ST team,
I am working on STM32WL55JC1. I am trying to enable the HSE external crystal oscillator, but it never starts.
In firmware, I configure RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE; and set HSEState = RCC_HSE_ON. After enabling, I confirmed that HSEON set, however HSERDY flag in RCC->CR never becomes set.
I have tried:
- Both Crystal/Ceramic Resonator mode and Bypass mode in CubeMX. In Bypass mode with external clock it works but in Crystal mode failed.
- Using HAL_RCC_OscConfig() followed by HAL_RCC_ClockConfig().
- Forcing HSE output on MCO pin (PA8) → no signal observed.
Hardware Verification Done:
- External 32 MHz crystal (NX2016SA-32M-EXS00A) with correct load capacitors (as per datasheet).
- Verified soldering, power rails, and grounding.
- Crystal reference design followed exactly (same as ST Nucleo-WL55 board).
- Supply voltage and decoupling capacitors confirmed OK.
Attempts Made:
- Full chip erase + reflash minimal firmware that just enables HSE and outputs it on MCO.
- Checked BOOT0 and reset conditions.
- Verified RCC_CR shows HSEON = 1 but HSERDY = 0.
- Tried lowering load capacitance and even replacing the crystal.
- Tested on two separate boards with identical result.
Could you please confirm:
- If there are any known issues with HSE startup on STM32WL55JC1 devices?
- If additional configuration (debug auth, option bytes, special modes) is required to enable HSE?
- it would be really helpful if you provide any reference example to enable HSE clock, I tried LoRa end-node example, clock configuration using STM32cubeMx.
Thanks,
Shivangi
