一、串口低功耗模式介绍
. v+ ~9 I, E7 t# N/ a- r: I1.1 介绍
+ w! t1 H9 {: E! ystm32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。

2 m. a! v5 g5 Z- w# p, S  H/ [1.2 三种模式和相关的寄存器
) e) P8 ^- {8 N1 w1.2.1 寄存器
% _! c3 r  j, [2 A! P6 ]5 Q1.2.1.1 CR3[21:20] WUS[1:0]
" u; l, A4 N# _' i, k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
' P! U/ d! H# |9 I* P01：保留
10：检测起始位
. p" ^& I* z; I' [: u11：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：
8 a5 \; p. f" R* K' T0：关闭中断
1：使能WUF中断，即当ISR的WUF为1时产生一个中断
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1.2.1.3 CR1[1] UESM
功能：使能串口的低功耗模式
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0：串口不能唤醒低功耗模式
1：串口能唤醒低功耗模式
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1.2.1.4 PWR_CR1[2:0] LPMS[2:0]
功能：低功耗模式选择
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; ]9 [- |+ O8 t) b/ V4 T000：stop 0模式
8 a9 j+ R1 A9 }* q001：stop1模式
010：保留
011：stanby模式

& Y' l. N; X( {" i7 e. `  x1.2.1.5 SCB_SCR[2] SLEEPDEEP
2 h" G5 ]" h; V% O, e# l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：
+ \" ^! f. W4 B0：睡眠模式
; }- b+ w: a+ ]9 C) m1：深度睡眠模式
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4 K2 z# I* ~) ?% G3 J, _1.2.2 模式
地址匹配模式
检测起始位
3 L5 [# K" Z0 _! eRXNE/RXFNE中断模式
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) o7 U) }6 A3 h0 C二、用法
7 O" a7 C- J# _2 y$ K& u' }1 b2.1 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。
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1. /* make sure that no LPUART transfer is on-going */
   
2.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
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3. 
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4.   /* make sure that LPUART is ready to receive
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5.    * (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
   
6.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
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7. 
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8.   /* set the wake-up event:
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9.    * specify address-to-match type.
   
10.    * The address is 0x29, meaning the character triggering the
    
11.    * address match is 0xA9 */
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12.   WakeUpSelection.WakeUpEvent   = UART_WAKEUP_ON_ADDRESS;
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13.   WakeUpSelection.AddressLength = UART_ADDRESS_DETECT_7B;
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14.   WakeUpSelection.Address       = 0x29;
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15.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
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16.   {
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17.     Error_Handler();
    
18.   }
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19. 
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20.   /* Enable the LPUART Wake UP from stop mode Interrupt */
    
21.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
    
22. 
    
23.   /* about to enter stop mode: switch off LED1 */
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24.   BSP_LED_Off(LED1);
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25.   /* enable MCU wake-up by LPUART */
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26.   HAL_UARTEx_EnableStopMode(&hlpuart1);
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27.   /* enter STOP mode */
    
28.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    
29. 
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30.   /* ... STOP mode ... */
    
31. 
    
32. 
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33.   /* at that point, MCU has been awoken: LED1 has been turned back on */
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34.   SystemClock_Config_fromSTOP();
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35. 
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36.   /* Wake Up on 7-bit address detection successful */
    
37.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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* c( t( k- j/ W8 e3 k2.2 起始位模式
串口上产生一个起始位可以唤醒。
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1. /* make sure that no LPUART transfer is on-going */
   
2.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
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3. 
   
4.   /* make sure that LPUART is ready to receive
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5.    * (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
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6.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
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7. 
   
8.   /* set the wake-up event:
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9.    * specify wake-up on start-bit detection */
   
10.   WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_STARTBIT;
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11.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
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12.   {
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13.     Error_Handler();
    
14.   }
    
15. 
    
16.   /* Enable the LPUART Wake UP from STOP mode Interrupt */
    
17.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
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18. 
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19.   /* about to enter STOP mode: switch off LED1 */
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20.   BSP_LED_Off(LED1);
    
21.   /* enable MCU wake-up by LPUART */
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22.   HAL_UARTEx_EnableStopMode(&hlpuart1);
    
23.   /* enter STOP mode */
    
24.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    
25. 
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26.   /* ... STOP mode ... */
    
27. 
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28. 
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29.   /* at that point, MCU has been awoken: LED1 has been turned back on */
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30.   SystemClock_Config_fromSTOP();
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31. 
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32.   /* Wake Up on start bit detection successful */
    
33.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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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。

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1. /* make sure that no LPUART transfer is on-going */
   
2.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_BUSY) == SET);
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3.   /* make sure that LPUART is ready to receive
   
4.    * (test carried out again later in HAL_UARTEx_StopModeWakeUpSourceConfig) */
   
5.   while (__HAL_UART_GET_FLAG(&hlpuart1, USART_ISR_REACK) == RESET);
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6. 
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7.   /* set the wake-up event:
   
8.    * specify wake-up on RXNE flag */
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9.   WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_READDATA_NONEMPTY;
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10.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
    
11.   {
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12.     Error_Handler();
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13.   }
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14. 
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15.   /* Enable the UART Wake UP from STOP mode Interrupt */
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16.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
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17. 
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18.   /* about to enter STOP mode: switch off LED1 */
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19.   BSP_LED_Off(LED1);
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20.   /* enable MCU wake-up by LPUART */
    
21.   HAL_UARTEx_EnableStopMode(&hlpuart1);
    
22.   /* enter STOP mode */
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23.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    
24. 
    
25.   /* ... STOP mode ... */
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26. 
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27. 
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28.   /* at that point, MCU has been awoken: LED1 has been turned back on */
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29.   SystemClock_Config_fromSTOP();
    
30. 
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31.   /* Wake Up based on RXNE flag successful */
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32.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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$ [+ M* \2 p* ?3 q# a0 [$ W2 j" m% G三、注意事项
, a0 d7 }/ {3 T% t3 H7 J% w! B如果使用地址匹配模式，需要关闭RXNE的中断。

1. 
   
2. __HAL_UART_DISABLE_IT(&huart1,UART_IT_RXNE);

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