关于低功耗蓝牙的连接参数更新

首先要明确：连接参数是由主机端确定的，从机端可以发起更新连接参数的请求。主机端可以直接下发连接参数，而从机端则只能是发起更新请求并附带想要的连接参数范围。

在初始化中将想要的连接参数设置进osal( 在和IOS设备连接时需要注意一些规则，在前面有提到 ):

GAPRole_SetParameter( GAPROLE_PARAM_UPDATE_ENABLE, sizeof( uint8 ), &enable_update_request );
GAPRole_SetParameter( GAPROLE_MIN_CONN_INTERVAL, sizeof( uint16 ), &desired_min_interval );
GAPRole_SetParameter( GAPROLE_MAX_CONN_INTERVAL, sizeof( uint16 ), &desired_max_interval );
GAPRole_SetParameter( GAPROLE_SLAVE_LATENCY, sizeof( uint16 ), &desired_slave_latency );
GAPRole_SetParameter( GAPROLE_TIMEOUT_MULTIPLIER, sizeof( uint16 ), &desired_conn_timeout );

追踪下GAPRole_SetParameter函数中这些参数的运作：

case GAPROLE_MIN_CONN_INTERVAL:
{
uint16 newInterval = *((uint16*)pValue);
if (   len == sizeof ( uint16 )           &&
( newInterval >= MIN_CONN_INTERVAL ) &&
( newInterval <= MAX_CONN_INTERVAL ) )
{
gapRole_MinConnInterval = newInterval;
}
else
{
ret = bleInvalidRange;
}
}
break;

都是存储在全局变量中，那么这些参数是何时发出去的呢？

且看：

在建立连接后会产生一个MSG然后在gapRole_ProcessGAPMsg函数中的GAP_LINK_PARAM_UPDATE_EVENT事件

gap.h中有对这一事件的介绍

case GAP_LINK_ESTABLISHED_EVENT:
{
gapEstLinkReqEvent_t *pPkt = (gapEstLinkReqEvent_t *)pMsg;

if ( pPkt->hdr.status == SUCCESS )
{
VOID osal_memcpy( gapRole_ConnectedDevAddr, pPkt->devAddr, B_ADDR_LEN );
gapRole_ConnectionHandle = pPkt->connectionHandle;
gapRole_state = GAPROLE_CONNECTED;

if ( gapRole_RSSIReadRate )
{
// Start the RSSI Reads
VOID osal_start_timerEx( gapRole_TaskID, RSSI_READ_EVT, gapRole_RSSIReadRate );
}

// Store connection information
gapRole_ConnInterval = pPkt->connInterval;
gapRole_ConnSlaveLatency = pPkt->connLatency;
gapRole_ConnTimeout = pPkt->connTimeout;

// Check whether update parameter request is enabled
if ( gapRole_ParamUpdateEnable == TRUE )
{
// Get the minimum time upon connection establishment before the
// peripheral can start a connection update procedure.
uint16 timeout = GAP_GetParamValue( TGAP_CONN_PAUSE_PERIPHERAL );

osal_start_timerEx( gapRole_TaskID, START_CONN_UPDATE_EVT, timeout*1000 );
}

// Notify the Bond Manager to the connection
VOID GAPBondMgr_LinkEst( pPkt->devAddrType, pPkt->devAddr, pPkt->connectionHandle, GAP_PROFILE_PERIPHERAL );

// Set enabler to FALSE; device will become discoverable again when
// this value gets set to TRUE
gapRole_AdvEnabled = FALSE;
}
else if ( pPkt->hdr.status == bleGAPConnNotAcceptable )
{
// Set enabler to FALSE; device will become discoverable again when
// this value gets set to TRUE
gapRole_AdvEnabled = FALSE;

// Go to WAITING state, and then start advertising
gapRole_state = GAPROLE_WAITING;
}
else
{
gapRole_state = GAPROLE_ERROR;
}
notify = TRUE;
}
break;

osal_start_timerEx( gapRole_TaskID, START_CONN_UPDATE_EVT, timeout*1000 );

这个事件便是发起连接参数更新，这个timeout是为了让连接更稳定，在建立连接之后得经过一段稳定的时间在更新参数

有网友的做法是在peripheralStateNotificationCB函数中的GAPROLE_CONNECTED里面添加更新参数的函数手动发起更新请求，不知这种做法是否有风险。

GAPRole_SendUpdateParam( uint16 minConnInterval, uint16 maxConnInterval,
uint16 latency, uint16 connTimeout, uint8 handleFailure );

也可以用下面这个中方式，两者本质都是用gapRole_startConnUpdate( GAPROLE_NO_ACTION );

GAPRole_SetParameter( GAPROLE_PARAM_UPDATE_REQ, sizeof ( uint8 ), TRUE );

怎么获取实时连接参数？

好办！

如下函数，注册一个回调函数，然后就可以得到connInterval，connSlaveLatency，connTimeout这三项参数，当参数更新成功是进入回调；因此可以在回调函数里面用LCD，打印，发给APP等等各种方式来展示

GAPRole_RegisterAppCBs( gapRolesParamUpdateCB_t *pParamUpdateCB );

顺便贴一下回调函数的调用：

case GAP_LINK_PARAM_UPDATE_EVENT:
{
gapLinkUpdateEvent_t *pPkt = (gapLinkUpdateEvent_t *)pMsg;

// Cancel connection param update timeout timer (if active)
VOID osal_stop_timerEx( gapRole_TaskID, CONN_PARAM_TIMEOUT_EVT );

if ( pPkt->hdr.status == SUCCESS )
{
// Store new connection parameters
gapRole_ConnInterval = pPkt->connInterval;
gapRole_ConnSlaveLatency = pPkt->connLatency;
gapRole_ConnTimeout = pPkt->connTimeout;

// Make sure there's no pending connection update procedure
if ( osal_get_timeoutEx( gapRole_TaskID, START_CONN_UPDATE_EVT ) == 0 )
{
// Notify the application with the new connection parameters
if ( pGapRoles_ParamUpdateCB != NULL )
{
(*pGapRoles_ParamUpdateCB)( gapRole_ConnInterval,
gapRole_ConnSlaveLatency,
gapRole_ConnTimeout );
}
}
}
}
break;

就写到这了，其他验证过会再更新

第一次写，有点乱。。。