Question
Crystal LSE startup problem on STM32F103RD
Posted on September 03, 2015 at 09:23
Hello,
We're using an STM32F103RD for one of our product and on which an extrenal crystal (768Khz) is connected on OSC32 In and ON (LSE). My problem is that this crystal only start to oscillate when the scope probe is touching the OSC32IN pin. The crystal is an ABS25-32768-6T, the load capacitor is 6pf (and tried with 2.2pF too) and the ext resistor is 0 ohm. To configure the F1 clock tree, I use the HAL function (version 1.0.1):__PWR_CLK_ENABLE();
__BKP_CLK_ENABLE();
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE | RCC_OSCILLATORTYPE_LSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.LSEState = RCC_LSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL3;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK|RCC_CLOCKTYPE_PCLK1 /*|RCC_CLOCKTYPE_PCLK2*/;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2; // DIV4
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1; //DIV2
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC;
PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);