STM32WBA 32MHz HSE. Can't Initialize HSE

[Pablo04]

Hi,

I made a custom PCB with a STM32WBA54CGU6 to act as a Bluetooth LE Audio transmitter. This was going to be first "real" PCB since before I have only made much simpler designs (I know I was very ambitious). For the HSE, I used this document to decide on the NX1612SA crystal oscillator. 

The problem I am facing is that I can't seem to get passed the SystemClock_Config() function call, more specifically, the HAL_RCC_OscConfig() function returns HAL_TIMEOUT in this part indicating that the HSE is not getting ready.

        /* Wait till HSE is ready */
        while (READ_BIT(RCC->CR, RCC_CR_HSERDY) == 0U)
        {
          if ((HAL_GetTick() - tickstart) > HSE_TIMEOUT_VALUE)
          {
            return HAL_TIMEOUT;
          }
        }
      }

 I know I have to trim the clock using the registers on the STM32 but I was unable to find how the value in the register maps to a specific capacitance. This led me trying every single possible value (0-63) but that made no difference. I have already resoldered a new crystal and a new STM32 so I am now believing the I have a layout issue in my PCB that's causing the crystal to not start. 

(The four pad footprint is the crystal connected to pins 40 and 41)

This is my layout and after some more research, I now think that I needed a ground "ring" and more vias returning to the ground plane around the crystal as recommended in this document. 

I also have confirmed the proper settings for the HSE setting to "Crystal/Ceramic Resonator" and to set the HSE clock to 32MHz in the Clock Configuration Tab of STM32CubeIDE.

I am asking for confirmation on my suspicions or ideas on other things I could test to get this to work. 

Thanks in advance.

[AScha.3]

Hi,

your crystal + layout looks ok.

>but I was unable to find how the value in the register maps to a specific capacitance

-> Refer to AN5042 for the HSE trimming procedure.

ok, just see rm :

(I dont have this chip...) Is there nothing to set the HSE in Cube ?

If not : set a value with "average" values , i would try : 

- before the start of the hse

- unlock register

- write 0x2FA0   (just guessing...try. or 2FF0, max drive) to RCC_HSECR

-> read AN2867 “Oscillator design guide for STM8S, STM8A and STM32

+ all voltage levels ok ? smps ...working?

[Pablo04 · Accepted solution]

Thanks for your response.

I saw the section in AN5042 about the HSETUNE[5:0] register already. What I meant by "a specific capacitance" was how the values, 0-63, correspond to a capacitance in pF. (Like how its stated for the STM32WL)

Anyways, from your comment about power, I double checked my schematic and realized I made a dumb mistake by forgetting to power up VDDRF which powers the HSE. 

I haven't been able to add a bodge wire yet but I'm assuming it will fix my problem.

Thanks for the help.