I am working with STM32L152VD. After waking up from sleep and switching to 8Mhz. everything work properly (SPI,I2C,..) except UART. I configure it using following function:
void uart1_configuration(void) { USART_InitTypeDef USART_InitStructure; GPIO_InitTypeDef GPIO_InitStructure; RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE); GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); /* Configure USART2 pins: Rx and Tx ----------------------------*/ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; 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); USART_InitStructure.USART_BaudRate = 9600; USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; USART_Init(USART1, &USART_InitStructure); USART_Cmd(USART1,ENABLE); /* Enable RXNE interrupt */ USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); /* Enable USART1 global interrupt */ NVIC_EnableIRQ(USART1_IRQn); }
It Seems UART is disabled.
I have used SystemCoreClockSetHSI(); to switch to high frequency. I measured this frequency from timers operation and concluded that it is exactly 8MHz. how ever it is still a question for me why it is not 16Mhz? this may be the issue USART fails to work.