文章目录
一、串口低功耗模式介绍
1.1 介绍
stm32可以通过串口来从stop模式唤醒，如果基于hal库，只要进行一些配置就能使用，这种通过串口唤醒的低功耗模式可以用在带电池的设备上，在需要设备工作的时候才将其唤醒处理事务，处理完后进入stop模式降低功耗。
1.2 三种模式和相关的寄存器
1.2.1 寄存器
1.2.1.1 CR3[21:20] WUS[1:0]
功能：选择从低功耗模式中断唤醒的标志
配置说明：
00：地址匹配模式
01：保留
10：检测起始位
11：RXNE/RXFNE中断
1.2.1.2 CR3[22] WUFIE
功能：使能从低功耗模式唤醒
配置说明：
0：关闭中断
1：使能WUF中断，即当ISR的WUF为1时产生一个中断
1.2.1.3 CR1[1] UESM
功能：使能串口的低功耗模式
配置说明：
0：串口不能唤醒低功耗模式
1：串口能唤醒低功耗模式
1.2.1.4 PWR_CR1[2:0] LPMS[2:0]
功能：低功耗模式选择
配置说明：
000：stop 0模式
001：stop1模式
010：保留
011：stanby模式
1.2.1.5 SCB_SCR[2] SLEEPDEEP
功能：决定处理器在低功耗模式时选择睡眠模式还是深度睡眠模式，SCB寄存器的内容在m0+编程手册里。
配置说明：
0：睡眠模式
1：深度睡眠模式
1.2.2 模式
地址匹配模式
检测起始位
RXNE/RXFNE中断模式
二、用法
2.1 地址匹配模式
地址配置成0x29（0010 1001），串口需要发送0xa9来唤醒，唤醒后需要关闭唤醒中断使能，重新初始化时钟。
/* make sure that no LPUART transfer is on-going */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
/* make sure that LPUART is ready to receive
* (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
/* set the wake-up event:
* specify address-to-match type.
* The address is 0x29, meaning the character triggering the
* address match is 0xA9 */
WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_ADDRESS;
WakeUpSelection.AddressLength = UART_ADDRESS_DETECT_7B;
WakeUpSelection.Address = 0x29;
if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
{
Error_Handler();
}
/* Enable the LPUART Wake UP from stop mode Interrupt */
__HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
/* about to enter stop mode: switch off LED1 */
BSP_LED_Off(LED1);
/* enable MCU wake-up by LPUART */
HAL_UARTEx_EnableStopMode(&hlpuart1);
/* enter STOP mode */
HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
/* ... STOP mode ... */
/* at that point, MCU has been awoken: LED1 has been turned back on */
SystemClock_Config_fromSTOP();
/* Wake Up on 7-bit address detection successful */
HAL_UARTEx_DisableStopMode(&hlpuart1);
2.2 起始位模式
串口上产生一个起始位可以唤醒。
/* make sure that no LPUART transfer is on-going */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
/* make sure that LPUART is ready to receive
* (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
/* set the wake-up event:
* specify wake-up on start-bit detection */
WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_STARTBIT;
if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
{
Error_Handler();
}
/* Enable the LPUART Wake UP from STOP mode Interrupt */
__HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
/* about to enter STOP mode: switch off LED1 */
BSP_LED_Off(LED1);
/* enable MCU wake-up by LPUART */
HAL_UARTEx_EnableStopMode(&hlpuart1);
/* enter STOP mode */
HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
/* ... STOP mode ... */
/* at that point, MCU has been awoken: LED1 has been turned back on */
SystemClock_Config_fromSTOP();
/* Wake Up on start bit detection successful */
HAL_UARTEx_DisableStopMode(&hlpuart1);
2.3 RXNE/RXFNE中断模式
接收到一个字符可以唤醒，接收的字节是完整的。
/* make sure that no LPUART transfer is on-going */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
/* make sure that LPUART is ready to receive
* (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
/* set the wake-up event:
* specify wake-up on RXNE flag */
WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_READDATA_NONEMPTY;
if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
{
Error_Handler();
}
/* Enable the UART Wake UP from STOP mode Interrupt */
__HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
/* about to enter STOP mode: switch off LED1 */
BSP_LED_Off(LED1);
/* enable MCU wake-up by LPUART */
HAL_UARTEx_EnableStopMode(&hlpuart1);
/* enter STOP mode */
HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
/* ... STOP mode ... */
/* at that point, MCU has been awoken: LED1 has been turned back on */
SystemClock_Config_fromSTOP();
/* Wake Up based on RXNE flag successful */
HAL_UARTEx_DisableStopMode(&hlpuart1);
三、注意事项
如果使用地址匹配模式，需要关闭RXNE的中断。
__HAL_UART_DISABLE_IT(&huart1,UART_IT_RXNE);