前言
最近有客户反映 STM32F103 进入 STOP 模式后无法通过串口唤醒。

一 问题分析
唤醒机制：在 MCU 进入 STOP 状态后，不能直接通过 UART 等中断外设唤醒，只能通过 EXTI 外部中断方式唤醒。但是我们可以在 MCU 进入 STOP 前将 RX 脚设为 EXTI 模式，并使能对应的中断来实现。相关代码在 STM3210B-EVAL 上测试可以实现该功能。

二 相关测试代码

1. int main(void)
   
2. {
   
3. #ifdef DEBUG
   
4. debug();
   
5. #endif
   
6. 
   
7. // System Init...
   
8. System_Init();
   
9. 
   
10. 
    
11. PWR_DeInit();
    
12. 
    
13. UART_Init();
    
14. 
    
15. // Global Variables Init...
    
16. Global_Variables_Init(); // + by dsg for global variables init...
    
17. while(1)
    
18. {
    
19. 
    
20. /* Request to enter STOP mode with regulator in low power mode*/
    
21. PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);
    
22. }
    
23. 
    
24. }
    
25. void EXTIX_Init(void)
    
26. {
    
27. EXTI_InitTypeDef EXTI_InitStructure;
    
28. NVIC_InitTypeDef NVIC_InitStructure;
    
29. RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);
    
30. GPIO_EXTILineConfig(GPIO_PortSourceGPIOB,GPIO_PinSource11);
    
31. EXTI_InitStructure.EXTI_Line=EXTI_Line11; //GPIOA.3 UART2_RX
    
32. EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    
33. EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
    
34. EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    
35. EXTI_Init(&EXTI_InitStructure);
    
36. 
    
37. NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQChannel;
    
38. NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x02;
    
39. NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x01;
    
40. NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    
41. NVIC_Init(&NVIC_InitStructure);
    
42. }
    
43. /*******************************************************************************
    
44. * Function Name : EXTI15_10_IRQHandler
    
45. * Description : This function handles External lines 15 to 10 interrupt request.
    
46. * Input : None
    
47. * Output : None
    
48. * Return : None
    
49. *******************************************************************************/
    
50. void EXTI15_10_IRQHandler(void)
    
51. {
    
52. EXTI_ClearITPendingBit(EXTI_Line11);
    
53. 
    
54. 
    
55. NVIC_GenerateSystemReset();
    
56. }
    
57. void PWR_EnterSTOPMode(u32 PWR_Regulator, u8 PWR_STOPEntry)
    
58. {
    
59. // Change the UART RX PIN to external interrupt mode
    
60. EXTIX_Init();
    
61. 
    
62. GPIO_ResetBits(GPIOC, GPIO_Pin_6);
    
63. GPIO_ResetBits(GPIOC, GPIO_Pin_7);
    
64. GPIO_ResetBits(GPIOC, GPIO_Pin_8);
    
65. 
    
66. u32 tmpreg = 0;
    
67. /* Check the parameters */
    
68. assert_param(IS_PWR_REGULATOR(PWR_Regulator));
    
69. assert_param(IS_PWR_STOP_ENTRY(PWR_STOPEntry));
    
70. 
    
71. /* Select the regulator state in STOP mode ---------------------------------*/
    
72. tmpreg = PWR->CR;
    
73. /* Clear PDDS and LPDS bits */
    
74. tmpreg &= CR_DS_Mask;
    
75. /* Set LPDS bit according to PWR_Regulator value */
    
76. tmpreg |= PWR_Regulator;
    
77. /* Store the new value */
    
78. PWR->CR = tmpreg;
    
79. /* Set SLEEPDEEP bit of Cortex System Control Register */
    
80. *(vu32 *) SCB_SysCtrl |= SysCtrl_SLEEPDEEP_Set;
    
81. 
    
82. /* Select STOP mode entry --------------------------------------------------*/
    
83. if(PWR_STOPEntry == PWR_STOPEntry_WFI)
    
84. {
    
85. /* Request Wait For Interrupt */
    
86. __WFI();
    
87. }
    
88. else
    
89. {
    
90. /* Request Wait For Event */
    
91. __WFE();
    
92. }
    
93. }
    
94. void UART_Init(void)
    
95. {
    
96. GPIO_InitTypeDef GPIO_InitStructure;
    
97. USART_InitTypeDef USART_InitStructure;
    
98. NVIC_InitTypeDef NVIC_InitStructure;
    
99. 
    
100. /* Enable USART3 clock */
     
101. RCC_APB1PeriphClockCmd( RCC_APB1Periph_USART3, ENABLE);
     
102. 
     
103. // GPIO Settings for USART3
     
104. // PB10: TXD_ROOM
     
105. GPIO_StructInit(&GPIO_InitStructure);
     
106. GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
     
107. GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
     
108. GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
     
109. GPIO_Init(GPIOB, &GPIO_InitStructure);
     
110. // PB11: RXD_ROOM
     
111. GPIO_StructInit(&GPIO_InitStructure);
     
112. GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
     
113. GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
     
114. //GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
     
115. GPIO_Init(GPIOB, &GPIO_InitStructure);
     
116. 
     
117. /* USARTx configuration ------------------------------------------------------*/
     
118. /* USARTx configured as follow:
     
119. - BaudRate = 600 baud
     
120. - Word Length = 8 Bits
     
121. - Two Stop Bit
     
122. - Even parity
     
123. - Hardware flow control disabled (RTS and CTS signals)
     
124. - Receive and transmit enabled
     
125. */
     
126. 
     
127. USART_DeInit(USART3);
     
128. USART_InitStructure.USART_BaudRate =9600;
     
129. USART_InitStructure.USART_WordLength = USART_WordLength_9b;
     
130. USART_InitStructure.USART_StopBits = USART_StopBits_2;
     
131. USART_InitStructure.USART_Parity = USART_Parity_Even;
     
132. USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
     
133. USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
     
134. USART_Init(USART3, &USART_InitStructure);
     
135. 
     
136. UartRxON();
     
137. 
     
138. // In initial state, waiting for indoor data...
     
139. USART_ITConfig(USART3, USART_IT_TXE, DISABLE);
     
140. USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
     
141. UART_State=UART_RX; //0; // 0: received state 1: transmit state
     
142. 
     
143. /* Enable the USART3 Interrupt */
     
144. NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQChannel;
     
145. NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;
     
146. NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
     
147. NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
     
148. NVIC_Init(&NVIC_InitStructure);
     
149. 
     
150. /* Enable USART3 */
     
151. USART_Cmd(USART3, ENABLE);
     
152. 
     
153. }
     

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