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
5 L3 g/ _; b, s1 ?) B, q" G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。

7 K* U) D) k' B4 p二 相关测试代码

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

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