OSAL的按键设计分析

痛定思痛。 2022-08-06 07:26 113阅读 0赞

转自：http://www.cnblogs.com/wsecurity/p/3259263.html

我们以按键的状态变化为线索，看看各个模块的作用，以及变量是怎么变化的。

按键设计总体上可以分为2部分，按键初始化和按键运行，按键初始化主要负责跟按键相关的IO端口设置、中断设置。按键运行就是OSAL检测按键的过程。

按键初始化

1、初始化按键

在main函数调用函数

void HalDriverInit (void);

HalDriverInit 对HAL层（硬件抽象层）做初始化，并在其内部调用

void HalKeyInit( void );

完成按键的初步初始化，按键初始化主要是把按键对应到IO口，并指定IO口的方向，并且把全局变量HalKeyConfigured设置为FALSE，这是因为虽然按键已经初始化了（指定了端口），但是还没有配置中断，也没有设置key的处理函数（用于向指定task发送key的消息）。

HalKeyInit函数对按键的初始化代码如下:

![复制代码][copycode.gif]

halKeySavedKeys = 0;  // Initialize previous key to 0.
      HAL_KEY_SW_6_SEL &= ~(HAL_KEY_SW_6_BIT);    /* Set pin function to GPIO */
      HAL_KEY_SW_6_DIR &= ~(HAL_KEY_SW_6_BIT);    /* Set pin direction to Input */
      HAL_KEY_JOY_MOVE_SEL &= ~(HAL_KEY_JOY_MOVE_BIT); /* Set pin function to GPIO */
      HAL_KEY_JOY_MOVE_DIR &= ~(HAL_KEY_JOY_MOVE_BIT); /* Set pin direction to Input */
      P2INP |= PUSH2_BV;  /* Configure GPIO tri-state. */
       /* Initialize callback function */
      pHalKeyProcessFunction  = NULL;//key的处理函数还未设置，需要在HalKeyConfig函数中设置
      /* Start with key is not configured */
      HalKeyConfigured = FALSE;

![复制代码][copycode.gif]

代码中将SW6按键绑定到了P0\_1端口，P0是一个8bit的端口，P0\_1是第二位。当读取P0口时，如果第二位为1，则为高电平，第二位为0，则为低电平。

2、配置按键

在main函数下调用HalDriverInit 函数完成按键初始化后，接着调用函数

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 </tbody> 
</table>

完成按键的配置。

InitBoard函数中执行按键配置，按键配置代码如下：

/* Initialize Key stuff */
        OnboardKeyIntEnable = HAL_KEY_INTERRUPT_ENABLE;           //打开中断
    
        //OnboardKeyIntEnable = HAL_KEY_INTERRUPT_DISABLE;
        HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);    //调用HalKeyConfig做按键配置，将OnBoard_KeyCallback作为按键处理函数。

HalKeyConfig的作用是设置按键回调函数、配置按键对应IO口的中断。

HalKeyConfig其实还能给OSAL发消息，但是只有在HalKeyConfigured = TRUE的时候才能发消息。因为在初始化按键的时候把HalKeyConfigured 设置为了FALSE，所以第一次调用HalKeyConfig不会发OSAL消息。

按键运行

当OSAL开始运行后，按键的状态有三种:

*  未按下
 *  按下的瞬间
 *  按下还未弹起

1、未按下

未按下时，OSAL处于等待中断触发的状态中，以P0口的中断为例，P0对应的是SW6按键，中断函数是：

2、按下的瞬间

当按键被按下，中断也被触发，这时候中断函数HAL\_ISR\_FUNCTION会调用按键中断处理函数

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对按键作出处理，并且调用osal\_start\_timerEx 函数在HAL\_KEY\_DEBOUNCE\_VALUE时间(25ms，防止按键抖动)后向OSAL的HAL task发出HAL\_KEY\_EVENT消息：

OSAL把这个消息发给Hal\_TaskID，Hal task会接受这个消息，继而调用Hal\_ProcessEvent函数，Hal\_ProcessEvent包括了多种硬件处理，例如LED UART KEY等，因为接受的消息是HAL\_KEY\_EVENT，所以进入按键处理分支：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

uint16 Hal_ProcessEvent( uint8 task_id, uint16 events )
    {
         .....//删略了其他HAL层收到的硬件消息，例如PERIOD_RSSI_RESET_EVT\HAL_LED_BLINK_EVENT等等
    
    if (events & HAL_KEY_EVENT)           //进入按键处理分支
      {
        /* Check for keys */
        HalKeyPoll();                               //读取按键的值
        /* if interrupt disabled, do next polling */
        if (!Hal_KeyIntEnable)
        {
          osal_start_timerEx( Hal_TaskID, HAL_KEY_EVENT, 100);
        }
        return events ^ HAL_KEY_EVENT;
      }
    }

![复制代码][copycode.gif]

Hal\_ProcessEvent在按键处理代码中，先调用HalKeyPoll函数读取key的值，HalKeyPoll函数对SW6按键的处理的代码如下

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

void HalKeyPoll (void)
    {
      uint8 keys = 0;
      uint8 notify = 0;
       if (!(HAL_KEY_SW_6_PORT & HAL_KEY_SW_6_BIT))    /* Key is active low */
      {
        keys |= HAL_KEY_SW_6;                //如果SW_6_PORT是低电平，则将keys的对应位设置为1
    
      }
       /* If interrupts are not enabled, previous key status and current key status
       * are compared to find out if a key has changed status.
       */
      if (!Hal_KeyIntEnable)
      {
        if (keys == halKeySavedKeys)
        {
          /* Exit - since no keys have changed */
          return;
        }
        else
        {
          notify = 1;
        }
      }
      else
      {
        /* Key interrupt handled here */
        if (keys)
        {
          notify = 1;
        }
      }
       /* Store the current keys for comparation next time */
      halKeySavedKeys = keys;
       /* Invoke Callback if new keys were depressed */
      if (notify && (pHalKeyProcessFunction))//pHalKeyProcessFunction实际上就是回调函数，在hal_drive中中使用
      {
        (pHalKeyProcessFunction) (keys, HAL_KEY_STATE_NORMAL);
      }
    }

![复制代码][copycode.gif]

HalKeyPoll首先判断sw6的端口是否按下，如果按下，此时HAL\_KEY\_SW\_6\_PORT是低电平，值为0。

然后，因为有keys!=0，并且开启了中断，需要将notify = 1。

最后，调用

pHalKeyProcessFunction是全局变量，在InitBoard中，已经调用HalKeyConfig将其设置为了OnBoard\_KeyCallback。

OnBoard\_KeyCallback函数如下：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

void OnBoard_KeyCallback ( uint8 keys, uint8 state )
    {
      uint8 shift;
      (void)state;
       // shift key (S1) is used to generate key interrupt
      // applications should not use S1 when key interrupt is enabled
      shift = (OnboardKeyIntEnable == HAL_KEY_INTERRUPT_ENABLE) ? false : ((keys & HAL_KEY_SW_6) ? true : false);
       if ( OnBoard_SendKeys( keys, shift ) != SUCCESS )//向注册的task发送按键消息
      {
        //blabla
      }
       /* If any key is currently pressed down and interrupt
         is still enabled, disable interrupt and switch to polling */
      if( keys != 0 )
      {
        if( OnboardKeyIntEnable == HAL_KEY_INTERRUPT_ENABLE )//如果开启了中断，将其设置为不开中断，接下来就按照每100ms调用一次keypoll
        {
          OnboardKeyIntEnable = HAL_KEY_INTERRUPT_DISABLE;
          HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);
        }
      }
      /* If no key is currently pressed down and interrupt
         is disabled, enable interrupt and turn off polling */
      else
      {
        if( OnboardKeyIntEnable == HAL_KEY_INTERRUPT_DISABLE )//如果key==0，并且中断关闭，则重新打开终端。
        {
          OnboardKeyIntEnable = HAL_KEY_INTERRUPT_ENABLE;
          HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);
        }
      }
    }

![复制代码][copycode.gif]

OnBoard\_KeyCallback主要做俩件事，调用OnBoard\_SendKeys函数将按键发送给注册过的task，也就是我们自己开发的task。OnBoard\_SendKeys代码如下：

![复制代码][copycode.gif]

uint8 OnBoard_SendKeys( uint8 keys, uint8 state )
    
    {
         ......
    
         osal_msg_send( registeredKeysTaskID, (uint8 *)msgPtr );//把按键消息发给注册ID registeredKeysTaskID的task
    
         ......
    }

![复制代码][copycode.gif]

OnBoard\_KeyCallback做的第二件事是开关中断，当按键触发中断后，OnBoard\_KeyCallback将中断关闭，这样在Hal\_ProcessEvent函数中将每100ms调用一次HalKeyPoll对key做轮询，并且在按键按下的过程中不再次进入OnBoard\_KeyCallback ，这样就不会再次向注册的task发出按键消息。

至此，按键按下瞬间完成，接下来进入的是按下还未弹起的状态。

3、按下还未弹起

在上一个按键按下瞬间状态， 调用了

关闭中断，此时会进入不配置中断的代码分支，如下：

![复制代码][copycode.gif]

else    /* Interrupts NOT enabled */
    {
        // 关闭中断
        HAL_KEY_SW_6_ICTL &= ~(HAL_KEY_SW_6_ICTLBIT); /* don't generate interrupt */
        HAL_KEY_SW_6_IEN &= ~(HAL_KEY_SW_6_IENBIT);   /* Clear interrupt enable bit */
         
    
         //给HAL task发送HAL_KEY_EVENT，进入key polling
        osal_set_event(Hal_TaskID, HAL_KEY_EVENT);
    }

![复制代码][copycode.gif]

接下来，由于给hal task发了消息，将进入hal的event处理函数

uint16 Hal_ProcessEvent( uint8 task_id, uint16 events );

因为event=HAL\_KEY\_EVENT，所以再次进入HAL\_KEY\_EVENT的处理代码：

![复制代码][copycode.gif]

if (events & HAL_KEY_EVENT)           //进入按键处理分支
    {
        /* Check for keys */
        HalKeyPoll();
         /* if interrupt disabled, do next polling */
        if (!Hal_KeyIntEnable)
        {
          osal_start_timerEx( Hal_TaskID, HAL_KEY_EVENT, 100);
        }
    }

![复制代码][copycode.gif]

跟前面处理中断不同的是，这次调用完HalKeyPoll()后，调用了：

osal_start_timerEx( Hal_TaskID, HAL_KEY_EVENT, 100);

启动了定时器，在100ms后，重新给Hal\_TaskID发送HAL\_KEY\_EVENT消息，重新进入polling。

现在反过来看看按下还未弹起状态下的的HalKeyPoll()做了什么：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

if (!Hal_KeyIntEnable)
      {
        if (keys == halKeySavedKeys)      //如果还是按下状态，则keys没有变化，此时不返回任何值。
        {
          /* Exit - since no keys have changed */
          return;
        }
        else
        {
          notify = 1;                               //如果按键弹起了，则将notify置1
        }
      }
        ....
    
    /* Store the current keys for comparation next time */
      halKeySavedKeys = keys;
       /* Invoke Callback if new keys were depressed */
      if (notify && (pHalKeyProcessFunction))           //如果还是按下状态，notify=0，此时不执行pHalKeyProcessFunction。
      {                                                                     //如果按键弹起，则进入pHalKeyProcessFunction
        (pHalKeyProcessFunction) (keys, HAL_KEY_STATE_NORMAL);
      }

![复制代码][copycode.gif]

如果按下状态没有改变，函数HalKeyPoll()不做任何事，当按键弹起，notify被置1，进入pHalKeyProcessFunction对按键做处理。

pHalKeyProcessFunction其实就是OnBoard\_KeyCallback，这个在前面的按键按下瞬间中分析过。现在来看看按键弹起时，OnBoard\_KeyCallback怎么处理的：

![复制代码][copycode.gif]

/* If no key is currently pressed down and interrupt
         is disabled, enable interrupt and turn off polling */
      else
      {
        if( OnboardKeyIntEnable == HAL_KEY_INTERRUPT_DISABLE )
        {
          OnboardKeyIntEnable = HAL_KEY_INTERRUPT_ENABLE;
          HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);
        }
      }

![复制代码][copycode.gif]

当key==0，并且中断关闭，这时候重新打开中断。等待下一次按键触发中断。

至此，整个按键过程执行了一轮。

[copycode.gif]: /images/20220806/c8d09f78d27b411fa0c0d1b2911feb1a.png
[ExpandedBlockStart.gif]: /images/20220806/f1d2150310f6487b9f42689ba6c9192c.png