Posted on October 10, 2016 at 14:08I have a STM32L051K8T6 which I am running from a 1.8v supply to interface with a Quectel UG95 modem. Project produced with STM32CubeMX. Code is compiled with Keil uVision 5.21a.
The firmware continually reboots about every 5 seconds (no watchdog implemented). Debugging with Keil reveals that SystemClock_Config is very slow completing and that after completion HCLK frequency is 2MHz. I take this to indicate that HSI did not start and the system has substituted the MSI clock.
Voltage scaling is set to Scale2 and SYSCLK is configured for a frequency of 8MHz
This is the code
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInit;
HAL_PWREx_EnableUltraLowPower();
/* Enable the fast wake up from Ultra low power mode */
HAL_PWREx_EnableFastWakeUp();
/* Select HSI as system clock source after Wake Up from Stop mode */
__HAL_RCC_WAKEUPSTOP_CLK_CONFIG(RCC_StopWakeUpClock_HSI);
__HAL_RCC_PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE2);
HAL_PWREx_DisableLowPowerRunMode();
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSE;
RCC_OscInitStruct.LSEState = RCC_LSE_ON;
RCC_OscInitStruct.HSIState = RCC_HSI_DIV4;
RCC_OscInitStruct.HSICalibrationValue = 16;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_8;
RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_4;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|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_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1|RCC_PERIPHCLK_USART2|RCC_PERIPHCLK_RTC;
PeriphClkInit.Usart1ClockSelection = RCC_USART1CLKSOURCE_PCLK2;
PeriphClkInit.Usart2ClockSelection = RCC_USART2CLKSOURCE_PCLK1;
PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit);
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(SysTick_IRQn);
}
I have checked STM32L0xx_hal_conf.h and this shows VDD_VALUE as 1800mV. The actual supply voltage is 1.803V.
What have I missed out or done wrong?
The original prototype used a STM32L051K8T7 which is the same processor but with extended operating temperature range and this works. I am assuming that it was a little more tolerant of the low voltage.
#hsi #stm32l05xx #1.8v
