STM32 external oscillator tcxo

Yes, no connection of OSC_OUT is required, not sure it's usable as a GPIO (might be a stated fact, or errata, don't recall), and you should enable BYPASS so nothing is output via OSC_OUT

Thank you ! I etched a test board but the software blocks at the ''waiting PLLRDY'' loop. I had a terrible time finding STM32+XO documentation, schematic or recommended parts so wouldthere be a problem with a 26Mhz, clipped sine wave, 0.8Vpp VCTCXO with a 0.1nF bypass capacitor between XO-VCC and GND and a 1000pF DC-blocking capacitor between XO-OUTPUT and OSC_IN ? Am I missing any component ?

http://i.imgur.com/KMXgSsO.jpg

http://www.ndk.com/cataloge/co12_NT3225SA_AFC_e1.pdf

/* Configure the main PLL clock source, multiplication and division factors. */
__HAL_RCC_PLL_CONFIG(RCC_OscInitStruct->PLL.PLLSource,
RCC_OscInitStruct->PLL.PLLM,
RCC_OscInitStruct->PLL.PLLN,
RCC_OscInitStruct->PLL.PLLP,
RCC_OscInitStruct->PLL.PLLQ);
/* Enable the main PLL. */
__HAL_RCC_PLL_ENABLE();
/* Get Start Tick*/
tickstart = HAL_GetTick();
/* Wait till PLL is ready */
while
(__HAL_RCC_GET_FLAG(RCC_FLAG_PLLRDY) == RESET)

But what PLL settings are you using?

RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 26;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);

With ON instead of BYPASS, the software doesn't infinite loop waiting for PLLRDY.

RCC_OscInitStruct.HSEState = RCC_HSE_ON;

Not a HAL guy, but in SPL we'd get the HSE out PA8 with

/* Output HSE clock on MCO1 pin(PA8) ****************************************/
/* Enable the GPIOA peripheral */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
/* Configure MCO1 pin(PA8) in alternate function */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* HSE clock selected to output on MCO1 pin(PA8)*/
RCC_MCO1Config(RCC_MCO1Source_HSE, RCC_MCO1Div_1);

I tried DSP V1.4 and the same problem arise : infinite loop waiting for RCC_CR_PLLRDY if BYPASS is set, no loop if BYPASS is not set.

Hello, I haven't had access to testing equipments yet but I'd like to understand the BYPASS flag better. With BYPASS set ''waiting PLLRDY'' loops, without it : SystemInit, TIM, USB, SDIO and FMC work fine.