一、串口低功耗模式介绍
# Z- v+ o+ J* e1 R: e0 x+ n1.1 介绍
# v. w; a; a1 V! k& r7 x6 K& zstm32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。

& E4 e$ d, m7 p2 K+ }1 x1.2 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]
/ F9 K; @/ ?8 d. z% q功能：选择从低功耗模式中断唤醒的标志
) u" h* i' `; P配置说明：
( x3 F# e% R# c* g0 Q- p& i* G00：地址匹配模式
01：保留
7 E. L1 t8 b! y3 G2 P10：检测起始位
11：RXNE/RXFNE中断

3 ]. E$ e* A5 ?" l1.2.1.2 CR3[22] WUFIE
. T0 h! N2 ^; S0 A功能：使能从低功耗模式唤醒
  j* y  ?7 R0 U. I! u& \) Y配置说明：
6 V  R$ K0 T* ]4 i, q% b8 `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
" E3 X+ D1 `) H2 r  R' j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
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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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! e. l3 [7 y$ b9 [) F000：stop 0模式
- C0 N4 q& L( K- r+ Y! `0 L% B- _001：stop1模式
010：保留
011：stanby模式

" S7 r2 n( i) S! R% |' v' Y5 J! ~9 ?1.2.1.5 SCB_SCR[2] SLEEPDEEP
( L2 ~. k1 V$ }# p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。
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& r, Z+ x# `2 Q: X% ~# g0：睡眠模式
4 e& c  @  |% U0 K# B1：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
RXNE/RXFNE中断模式
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二、用法
, h1 R5 q- A3 u2.1 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. 
   
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:
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9.    * specify address-to-match type.
   
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;
    
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.   }
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19. 
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20.   /* Enable the LPUART Wake UP from stop mode Interrupt */
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21.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
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22. 
    
23.   /* about to enter stop mode: switch off LED1 */
    
24.   BSP_LED_Off(LED1);
    
25.   /* enable MCU wake-up by LPUART */
    
26.   HAL_UARTEx_EnableStopMode(&hlpuart1);
    
27.   /* enter STOP mode */
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28.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
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29. 
    
30.   /* ... STOP mode ... */
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31. 
    
32. 
    
33.   /* at that point, MCU has been awoken: LED1 has been turned back on */
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34.   SystemClock_Config_fromSTOP();
    
35. 
    
36.   /* Wake Up on 7-bit address detection successful */
    
37.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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2.2 起始位模式
; G$ \4 Q8 T. s) ^2 u. `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 */
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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
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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:
   
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)
    
12.   {
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13.     Error_Handler();
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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);
    
18. 
    
19.   /* about to enter STOP mode: switch off LED1 */
    
20.   BSP_LED_Off(LED1);
    
21.   /* enable MCU wake-up by LPUART */
    
22.   HAL_UARTEx_EnableStopMode(&hlpuart1);
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23.   /* enter STOP mode */
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24.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    
25. 
    
26.   /* ... STOP mode ... */
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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 */
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33.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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$ {7 k: {' X# \2 s% P2.3 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);
   
3.   /* make sure that LPUART is ready to receive
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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. 
   ' ~! Y) O4 j: Q1 F7 q. q; ]
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.   {
    
12.     Error_Handler();
    
13.   }
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14. 
    
15.   /* Enable the UART Wake UP from STOP mode Interrupt */
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16.   __HAL_UART_ENABLE_IT(&hlpuart1, UART_IT_WUF);
    
17. 
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18.   /* about to enter STOP mode: switch off LED1 */
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19.   BSP_LED_Off(LED1);
    
20.   /* enable MCU wake-up by LPUART */
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21.   HAL_UARTEx_EnableStopMode(&hlpuart1);
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22.   /* enter STOP mode */
    
23.   HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
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24. 
    
25.   /* ... STOP mode ... */
    
26. 
    
27. 
    
28.   /* at that point, MCU has been awoken: LED1 has been turned back on */
    
29.   SystemClock_Config_fromSTOP();
    
30. 
    
31.   /* Wake Up based on RXNE flag successful */
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32.   HAL_UARTEx_DisableStopMode(&hlpuart1);

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6 z6 P- A5 L: ?2 s$ z0 [/ p三、注意事项
5 @: o3 n7 u* i9 @* h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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