一、串口低功耗模式介绍
1.1 介绍
, E0 }3 O) M6 Kstm32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。

0 o/ W3 @  F3 y1.2 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：
3 ]% y. l! O# ~& A' s00：地址匹配模式
01：保留
10：检测起始位
11：RXNE/RXFNE中断

2 Y) @3 @4 V# k1.2.1.2 CR3[22] WUFIE
功能：使能从低功耗模式唤醒
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* q  C7 h' I7 [3 A, I! f4 c- 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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" w! {" h0 Y1 k1.2.1.3 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

- x; g, s" Q4 N6 Y+ L' U1.2.1.4 PWR_CR1[2:0] LPMS[2:0]
6 m6 ]/ I9 y6 T) L6 P功能：低功耗模式选择
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000：stop 0模式
2 G; O4 L, T' o2 T001：stop1模式
010：保留
- H2 b3 L, j: T0 e011：stanby模式
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& T& P  u5 L. T" Z( D4 H5 ^1.2.1.5 SCB_SCR[2] SLEEPDEEP
1 C* n/ ?8 W, @" @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
  o0 c) Q2 ]* G( Y5 ~, R/ e, ^1：深度睡眠模式
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1.2.2 模式
地址匹配模式
检测起始位
6 L7 R# ?3 ~) S& HRXNE/RXFNE中断模式

二、用法
2.1 地址匹配模式
( c' H8 Z6 G* C9 B* R" l/ {! R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 */
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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
   
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:
   
9.    * specify address-to-match type.
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10.    * The address is 0x29, meaning the character triggering the
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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;
    
15.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
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16.   {
    
17.     Error_Handler();
    
18.   }
    
19. 
    
20.   /* Enable the LPUART Wake UP from stop mode Interrupt */
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21.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
    
22. 
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23.   /* about to enter stop mode: switch off LED1 */
    
24.   BSP_LED_Off(LED1);
    
25.   /* enable MCU wake-up by LPUART */
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26.   HAL_UARTEx_EnableStopMode(&hlpuart1);
    
27.   /* enter STOP mode */
    
28.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    
29. 
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30.   /* ... STOP mode ... */
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31. 
    
32. 
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33.   /* at that point, MCU has been awoken: LED1 has been turned back on */
    
34.   SystemClock_Config_fromSTOP();
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35. 
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36.   /* Wake Up on 7-bit address detection successful */
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37.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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0 \8 ~9 G8 T4 e/ E3 R2.2 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. 
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4.   /* make sure that LPUART is ready to receive
   
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);
   
7. 
   
8.   /* set the wake-up event:
   
9.    * specify wake-up on start-bit detection */
   
10.   WakeUpSelection.WakeUpEvent = UART_WAKEUP_ON_STARTBIT;
    
11.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
    
12.   {
    
13.     Error_Handler();
    
14.   }
    
15. 
    
16.   /* Enable the LPUART Wake UP from STOP mode Interrupt */
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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 */
    
20.   BSP_LED_Off(LED1);
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21.   /* enable MCU wake-up by LPUART */
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22.   HAL_UARTEx_EnableStopMode(&hlpuart1);
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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 */
    
30.   SystemClock_Config_fromSTOP();
    
31. 
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32.   /* Wake Up on start bit detection successful */
    
33.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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, j2 A: e' A9 C* u" P; t& n9 W& t! u- W2.3 RXNE/RXFNE中断模式
& R- M" l: S1 n# P3 Q" z0 d2 `" X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 */
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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);
   
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;
   
10.   if (HAL_UARTEx_StopModeWakeUpSourceConfig(&hlpuart1, WakeUpSelection) != HAL_OK)
    
11.   {
    
12.     Error_Handler();
    
13.   }
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14. 
    
15.   /* Enable the UART Wake UP from STOP mode Interrupt */
    
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 */
    
19.   BSP_LED_Off(LED1);
    
20.   /* enable MCU wake-up by LPUART */
    
21.   HAL_UARTEx_EnableStopMode(&hlpuart1);
    
22.   /* enter STOP mode */
    
23.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
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24. 
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25.   /* ... STOP mode ... */
    
26. 
    
27. 
    
28.   /* at that point, MCU has been awoken: LED1 has been turned back on */
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29.   SystemClock_Config_fromSTOP();
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30. 
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31.   /* Wake Up based on RXNE flag successful */
    
32.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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) x+ ]9 }2 z8 `- a1 n" i" \三、注意事项
如果使用地址匹配模式，需要关闭RXNE的中断。
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1. 
   
2. __HAL_UART_DISABLE_IT(&huart1,UART_IT_RXNE);

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