Modem Call Control

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Starting a Call

To initiate a call, create a new call object with a destination telephone number calling the le_mcc_profile_CreateCall() function.

le_mcc_call_Start() must still initiate the call when ready.

The le_mcc_call_Start() function initiates a call attempt (it's asynchronous because it can take time for a call to connect).

It's essential to register a handler function to get the call events. Use le_mcc_profile_AddCallEventHandler() API to install that handler function. As the call attempt proceeds, the profile's registered call event handler will receive events.

The le_mcc_profile_RemoveCallEventHandler() API uninstalls the handler function.

The following APIs can be used to manage incoming or outgoing calls:

• le_mcc_call_GetTerminationReason() - termination reason.
• le_mcc_call_IsConnected() - connection status.
• le_mcc_call_GetRemoteTel() - displays remote party telephone number associated with the call.
• le_mcc_call_GetRxAudioStream() must be called to receive audio stream for this call. Audio received from the other end of the call uses this stream.
• le_mcc_call_GetTxAudioStream() must be called to transmit audio stream this call. Audio generated on this end is sent on this stream.
• le_mcc_call_HangUp() will disconnect this call.

When finished with the call object, call le_mcc_call_Delete() to free all the allocated resources associated with the object. This will frees the reference, but remains active if other holders are using it.

This code example uses CallAndPlay() to dial a phone number, and if successful, play a sound file. Once the file has played, the call hangs up.

typedef struct
{
    le_mcc_profile_ObjRef_t profileRef;
    le_mcc_call_ObjRef_t    callRef;
    char                    filePath[MAX_FILE_PATH_BYTES];
}
PlayContext_t;

void CallAndPlay
(
    const char* destinationTelPtr,
    const char* filePathPtr
)
{
    PlayContext_t* contextPtr = (PlayContext_t*)le_mem_ForceAlloc(PlayContextPoolRef);

    le_str_Copy(contextPtr->filePath, filePathPtr, sizeof(contextPtr->filePath), NULL);

    contextPtr->profileRef = le_mcc_profile_GetByName("Modem-Sim1");

    le_mcc_profile_AddCallEventHandler(contextPtr->profileRef,
                                       MyCallEventHandler,
                                       contextPtr);

    contextPtr->callRef = le_mcc_profile_CreateCall(contextPtr->profileRef, destinationTelPtr);

    le_mcc_call_Start(contextPtr->callRef);
}


static void MyCallEventHandler
(
    le_mcc_call_ObjRef_t callRef,
    le_mcc_call_Event_t  event,
    void*                contextPtr
)
{
    PlayContext_t*      myContextPtr = (PlayContext_t*)contextPtr;

    switch (event)
    {
        case LE_MCC_CALL_EVENT_CONNECTED:
            {
                le_audio_StreamRef_t callAudioTxRef = le_mcc_call_GetTxAudioStream(callRef);

                le_audio_PlaySoundFromFile(callAudioTxRef,
                                           myContextPtr->filePath,
                                           MyAudioFinishedHandler,
                                           myContextPtr);
            }
            break;

        case LE_MCC_CALL_EVENT_TERMINATED:
            le_mcc_call_Delete(callRef);
            // I don't release the Profile for further use

            le_mcc_profile_RemoveCallEventHandler(myContextPtr->profileRef);

            le_mem_Release(myContextPtr);
            break;
    }
}


static void MyAudioFinishedHandler
(
    le_audio_PlayComplete reason,
    void*                 contextPtr
)
{
    PlayContext_t* myContextPtr = (PlayContext_t*)contextPtr;

    le_mcc_call_HangUp(myContextPtr->callRef);  // This will trigger a TERMINATED event.
}

Answering a call

Receiving calls is similar sending calls. Add a handler through le_mcc_profile_AddCallEventHandler() to be notified of incoming calls.

To answer, call le_mcc_call_Answer(). To reject it, call le_mcc_call_Delete().

This code example uses InstallAutomaticAnswer() to install a call event handler that automatically answers incoming calls. The handler function verifies the incoming call is permitted (through a predefined list), and then decides whether to answer or terminate it. If a call is already active, it can add the new incoming call creating a conference call.

typedef struct
{
    le_mcc_profile_ObjRef_t profileRef;
    le_mcc_call_ObjRef_t    callRef;
    uint32_t                calledPartyCount;
}
VoiceContext_t;

static le_audio_ConnectorRef_t AudioRxConnectorRef = NULL;
static le_audio_ConnectorRef_t AudioTxConnectorRef = NULL;


void InstallAutomaticAnswer
(
    void
)
{
    VoiceContext_t* contextPtr = (VoiceContext_t*)le_mem_ForceAlloc(VoiceContextPoolRef);

    contextPtr->profileRef = le_mcc_profile_GetByName("Modem-Sim1");

    le_mcc_profile_AddCallEventHandler(contextPtr->profileRef,
                                       MyVoiceCallEventHandler,
                                       contextPtr);
}


static void MyVoiceCallEventHandler
(
    le_mcc_call_ObjRef_t callRef,
    le_mcc_call_Event_t  event,
    void*                contextPtr
)
{
    char                tel[TEL_NMBR_MAX_LEN];
    VoiceContext_t*     myContextPtr = (VoiceContext_t*)contextPtr;

    switch (event)
    {
        case LE_MCC_CALL_EVENT_INCOMING:
            {
                le_mcc_profile_State_t myProfileState = LE_MCC_PROFILE_NOT_AVAILABLE;

                le_mcc_call_GetRemoteTel(callRef, &tel, sizeof(tel));
                if (IsAnAuthorizedIncomingCall(tel) == TRUE)
                {
                    le_mcc_profile_GetState(myProfile, &myProfileState);
                    if(myProfileState == LE_MCC_PROFILE_IN_USE)
                    {
                        // Another incoming call, turn this into a x-way conference, mixed locally:
                        myContextPtr->calledPartyCount++;

                        le_audio_StreamRef_t otherCallRxAudioRef = le_mcc_call_GetRxAudioStream(callRef);
                        le_audio_StreamRef_t otherCallTxAudioRef = le_mcc_call_GetTxAudioStream(callRef);

                        le_audio_connector_AddStream(AudioRxConnectorRef, otherCallRxAudioRef);
                        le_audio_connector_AddStream (AudioTxConnectorRef, otherCallTxAudioRef);
                    }
                    else if(myProfileState == LE_MCC_PROFILE_IDLE)
                    {
                        // First incoming call
                        myContextPtr->calledPartyCount = 1;

                        le_audio_StreamRef_t speakerphoneRef = le_audio_OpenSpeakerphone();
                        le_audio_StreamRef_t callRxAudioRef = le_mcc_call_GetRxAudioStream(callRef);
                        le_audio_StreamRef_t micphoneRef = le_audio_OpenMicphone();
                        le_audio_StreamRef_t callTxAudioRef = le_mcc_call_GetTxAudioStream(callRef);

                        AudioRxConnectorRef = le_audio_CreateConnector();
                        AudioTxConnectorRef = le_audio_CreateConnector();

                        le_audio_connector_AddStream(AudioRxConnectorRef, speakerphoneRef);
                        le_audio_connector_AddStream (AudioRxConnectorRef, callRxAudioRef);

                        le_audio_connector_AddStream(AudioTxConnectorRef, micphoneRef);
                        le_audio_connector_AddStream (AudioTxConnectorRef, callTxAudioRef);
                    }

                    le_mcc_call_Answer(callRef);
                }
                else
                {
                    // Reject the incoming call
                    le_mcc_call_Delete(callRef);
                }
             }
             break;

         case LE_MCC_CALL_EVENT_TERMINATED:
             le_mcc_call_Delete(callRef);

             // I delete the Audio connector references if it remains only one called party.
             if (myContextPtr->calledPartyCount == 1)
             {
                 le_audio_DeleteConnector(AudioRxConnectorRef);
                 le_audio_DeleteConnector(AudioTxConnectorRef);
             }
             else
             {
                 myContextPtr->calledPartyCount--;
             }
             break;
     }
 }

Ending all calls

A special function can be used to hang-up all the ongoing calls: le_mcc_call_HangUpAll(). This function can be used to hang-up any calls that have been initiated through another client like AT commands.

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Copyright (C) Sierra Wireless, Inc. 2014. Use of this work is subject to license.