我用STM32Cubemx生成keil项目，用到了ADC，于是查看stm32f0xx_hal_adc.c.中的HAL_StatusTypeDef HAL_ADC_PollForConversion(ADC_HandleTypeDef* hadc, uint32_t Timeout)函数，不明白Timeout参数是干什么用的，，Timeout我试过用不同的值，但是效果都一样，没什么区别

该函数如下：

1. /**
   
2.   * @brief  Wait for regular group conversion to be completed.
   
3.   * @param  hadc: ADC handle
   
4.   * @param  Timeout: Timeout value in millisecond.
   
5.   * @retval HAL status
   
6.   */
   
7. HAL_StatusTypeDef HAL_ADC_PollForConversion(ADC_HandleTypeDef* hadc, uint32_t Timeout)
   
8. {
   
9.   uint32_t tickstart;
   
10.   uint32_t tmp_Flag_EOC;
    
11. 
    
12.   /* Check the parameters */
    
13.   assert_param(IS_ADC_ALL_INSTANCE(hadc->Instance));
    
14. 
    
15.   /* If end of conversion selected to end of sequence */
    
16.   if (hadc->Init.EOCSelection == EOC_SEQ_CONV)
    
17.   {
    
18.     tmp_Flag_EOC = ADC_FLAG_EOS;
    
19.   }
    
20.   /* If end of conversion selected to end of each conversion */
    
21.   else /* EOC_SINGLE_CONV */
    
22.   {
    
23.     tmp_Flag_EOC = (ADC_FLAG_EOC | ADC_FLAG_EOS);
    
24.   }
    
25.    
    
26.   /* Get timeout */
    
27.   tickstart = HAL_GetTick();  
    
28.      
    
29.   /* Wait until End of Conversion flag is raised */
    
30.   while(HAL_IS_BIT_CLR(hadc->Instance->ISR, tmp_Flag_EOC))
    
31.   {
    
32.     /* Check if timeout is disabled (set to infinite wait) */
    
33.     if(Timeout != HAL_MAX_DELAY)
    
34.     {
    
35.       if((Timeout == 0) || ((HAL_GetTick()-tickstart) > Timeout))
    
36.       {
    
37.         /* Update ADC state machine to timeout */
    
38.         hadc->State = HAL_ADC_STATE_TIMEOUT;
    
39.         
    
40.         /* Process unlocked */
    
41.         __HAL_UNLOCK(hadc);
    
42.         
    
43.         return HAL_ERROR;
    
44.       }
    
45.     }
    
46.   }
    
47.   
    
48.   /* Clear end of conversion flag of regular group if low power feature       */
    
49.   /* "LowPowerAutoWait " is disabled, to not interfere with this feature      */
    
50.   /* until data register is read using function HAL_ADC_GetValue().           */
    
51.   if (hadc->Init.LowPowerAutoWait == DISABLE)
    
52.   {
    
53.     /* Clear regular group conversion flag */
    
54.     __HAL_ADC_CLEAR_FLAG(hadc, (ADC_FLAG_EOC | ADC_FLAG_EOS));
    
55.   }
    
56.   
    
57.   /* Update state machine on conversion status if not in error state */
    
58.   if(hadc->State != HAL_ADC_STATE_ERROR)
    
59.   {
    
60.     /* Change ADC state */
    
61.     hadc->State = HAL_ADC_STATE_EOC_REG;
    
62.   }
    
63.   
    
64.   /* Return ADC state */
    
65.   return HAL_OK;
    
66. }
    

复制代码

请问Timeout有什么用？

打断while(HAL_IS_BIT_CLR(hadc->Instance->ISR, tmp_Flag_EOC))，退出这个loop的条件，代码更健壮。