LoRa開發|LoRaWAN節點(node)代碼解析（STM32L051+SX1276/8）安信可RHF76-052

一、前言

        嵌入式開發中我們要時刻保持代碼的高效與整潔。目前LoRaWAN規範有兩個版本V1.0.2和V1.0.3，相應的SDK也有兩個：LoRaMac-node v4.0.0和LoRaMac-node v4.4.2。LoRaMac-node v4.4.2增加了classB的通信方式，但是LoRaMac-node v4.4.2的內存佔用要比v4.0.0大一些，不過目前市面上買的LoRAWAN模組應該還是v1.0.2版本的。

二、代碼分析v4.0.0

LoRaMac應該是純軟件的東西，但是卻包含了硬件層的東西，全部讀完代碼就會發現官網的代碼一點都不友好，用了很多全局變量，而且main.c搞那麼大看着就很亂，也不知道官網是怎麼想的。

int main( void )
{
    LoRaMacPrimitives_t LoRaMacPrimitives;
    LoRaMacCallback_t LoRaMacCallbacks;
    MibRequestConfirm_t mibReq;

    BoardInitMcu( );
    BoardInitPeriph( );

    DeviceState = DEVICE_STATE_INIT;
	printf("LoRawan start\r\n");
    while( 1 )
    {
        switch( DeviceState )
        {
            case DEVICE_STATE_INIT:
            {
                LoRaMacPrimitives.MacMcpsConfirm = McpsConfirm;
                LoRaMacPrimitives.MacMcpsIndication = McpsIndication;
                LoRaMacPrimitives.MacMlmeConfirm = MlmeConfirm;
               // LoRaMacCallbacks.GetBatteryLevel = BoardGetBatteryLevel;
                LoRaMacInitialization( &LoRaMacPrimitives, &LoRaMacCallbacks );

                TimerInit( &TxNextPacketTimer, OnTxNextPacketTimerEvent );

                TimerInit( &Led1Timer, OnLed1TimerEvent );
                TimerSetValue( &Led1Timer, 25 );

                TimerInit( &Led2Timer, OnLed2TimerEvent );
                TimerSetValue( &Led2Timer, 25 );

                TimerInit( &Led4Timer, OnLed4TimerEvent );
                TimerSetValue( &Led4Timer, 25 );

                mibReq.Type = MIB_ADR;
                mibReq.Param.AdrEnable = LORAWAN_ADR_ON;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_PUBLIC_NETWORK;
                mibReq.Param.EnablePublicNetwork = LORAWAN_PUBLIC_NETWORK;
                LoRaMacMibSetRequestConfirm( &mibReq );

#if defined( USE_BAND_868 )
                LoRaMacTestSetDutyCycleOn( LORAWAN_DUTYCYCLE_ON );

#if( USE_SEMTECH_DEFAULT_CHANNEL_LINEUP == 1 )
                LoRaMacChannelAdd( 3, ( ChannelParams_t )LC4 );
                LoRaMacChannelAdd( 4, ( ChannelParams_t )LC5 );
                LoRaMacChannelAdd( 5, ( ChannelParams_t )LC6 );
                LoRaMacChannelAdd( 6, ( ChannelParams_t )LC7 );
                LoRaMacChannelAdd( 7, ( ChannelParams_t )LC8 );
                LoRaMacChannelAdd( 8, ( ChannelParams_t )LC9 );
                LoRaMacChannelAdd( 9, ( ChannelParams_t )LC10 );

                mibReq.Type = MIB_RX2_DEFAULT_CHANNEL;
                mibReq.Param.Rx2DefaultChannel = ( Rx2ChannelParams_t ){ 869525000, DR_3 };
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_RX2_CHANNEL;
                mibReq.Param.Rx2Channel = ( Rx2ChannelParams_t ){ 869525000, DR_3 };
                LoRaMacMibSetRequestConfirm( &mibReq );
#endif

#endif
                DeviceState = DEVICE_STATE_JOIN;
                printf("DEVICE_STATE_INIT \r\n");
                break;
            }
            case DEVICE_STATE_JOIN:
            {
#if( OVER_THE_AIR_ACTIVATION != 0 )
                MlmeReq_t mlmeReq;

                // Initialize LoRaMac device unique ID
                BoardGetUniqueId( DevEui );

                mlmeReq.Type = MLME_JOIN;

                mlmeReq.Req.Join.DevEui = DevEui;
                mlmeReq.Req.Join.AppEui = AppEui;
                mlmeReq.Req.Join.AppKey = AppKey;
                mlmeReq.Req.Join.NbTrials = 3;

                if( NextTx == true )
                {
                    LoRaMacMlmeRequest( &mlmeReq );
                }
                DeviceState = DEVICE_STATE_SLEEP;
#else
                // Choose a random device address if not already defined in Commissioning.h
                if( DevAddr == 0 )
                {
                    // Random seed initialization
                    srand1( BoardGetRandomSeed( ) );

                    // Choose a random device address
                    DevAddr = randr( 0, 0x01FFFFFF );
                }

                mibReq.Type = MIB_NET_ID;
                mibReq.Param.NetID = LORAWAN_NETWORK_ID;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_DEV_ADDR;
                mibReq.Param.DevAddr = DevAddr;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_NWK_SKEY;
                mibReq.Param.NwkSKey = NwkSKey;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_APP_SKEY;
                mibReq.Param.AppSKey = AppSKey;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_NETWORK_JOINED;
                mibReq.Param.IsNetworkJoined = true;
                LoRaMacMibSetRequestConfirm( &mibReq );

                DeviceState = DEVICE_STATE_SEND;
#endif
                printf("DEVICE_STATE_JOIN \r\n");
                break;
            }
            case DEVICE_STATE_SEND:
            {
                if( NextTx == true )
                {
                    PrepareTxFrame( AppPort );

                    NextTx = SendFrame( );
                }
                if( ComplianceTest.Running == true )
                {
                    // Schedule next packet transmission
                    TxDutyCycleTime = 5000; // 5000 ms
                }
                else
                {
                    // Schedule next packet transmission
                    TxDutyCycleTime = APP_TX_DUTYCYCLE + randr( -APP_TX_DUTYCYCLE_RND, APP_TX_DUTYCYCLE_RND );
                }
                DeviceState = DEVICE_STATE_CYCLE;
                printf("DEVICE_STATE_SEND \r\n");
                break;
            }
            case DEVICE_STATE_CYCLE:
            {
                DeviceState = DEVICE_STATE_SLEEP;

                // Schedule next packet transmission
                TimerSetValue( &TxNextPacketTimer, TxDutyCycleTime );
                TimerStart( &TxNextPacketTimer );
                printf("DEVICE_STATE_CYCLE \r\n");
                break;
            }
            case DEVICE_STATE_SLEEP:
            {
                // Wake up through events
				//printf("DEVICE_STATE_SLEEP \r\n");
                TimerLowPowerHandler( );
                break;
            }
            default:
            {
                DeviceState = DEVICE_STATE_INIT;
                break;
            }
        }
//        if( GpsGetPpsDetectedState( ) == true )
//        {
//            // Switch LED 4 ON
//            GpioWrite( &Led4, 0 );
//            TimerStart( &Led4Timer );
//        }
    }
}

主函數就是狀態之間的切換，狀態機採用的switch語句

static enum eDeviceState
{
    DEVICE_STATE_INIT,
    DEVICE_STATE_JOIN,
    DEVICE_STATE_SEND,
    DEVICE_STATE_CYCLE,
    DEVICE_STATE_SLEEP
}DeviceState;

三、入網方式

        如果是空中OTAA激活，則需要準備 DevEUI，AppEUI，AppKey 這三個參數，即設備自身MAC地址和要使用的應用(應用ID和密鑰)。
        如果是ABP激活，則直接配置 DevAddr，NwkSKey，AppSKey 這三個LoRaWAN最終通訊的參數，不再需要join流程。在這種情況下，這個設備是可以直接發應用數據的。

       代碼用一個宏(OVER_THE_AIR_ACTIVATION)分開兩段，分別對應兩種激活方式。OVER_THE_AIR_ACTIVATION ！=0爲OTAA空中激活方式。

case DEVICE_STATE_JOIN:
            {
#if( OVER_THE_AIR_ACTIVATION != 0 )
                MlmeReq_t mlmeReq;

                // Initialize LoRaMac device unique ID
                BoardGetUniqueId( DevEui );

                mlmeReq.Type = MLME_JOIN;

                mlmeReq.Req.Join.DevEui = DevEui;
                mlmeReq.Req.Join.AppEui = AppEui;
                mlmeReq.Req.Join.AppKey = AppKey;
                mlmeReq.Req.Join.NbTrials = 3;

                if( NextTx == true )
                {
                    LoRaMacMlmeRequest( &mlmeReq );
                }
                DeviceState = DEVICE_STATE_SLEEP;
#else
                // Choose a random device address if not already defined in Commissioning.h
                if( DevAddr == 0 )
                {
                    // Random seed initialization
                    srand1( BoardGetRandomSeed( ) );

                    // Choose a random device address
                    DevAddr = randr( 0, 0x01FFFFFF );
                }

                mibReq.Type = MIB_NET_ID;
                mibReq.Param.NetID = LORAWAN_NETWORK_ID;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_DEV_ADDR;
                mibReq.Param.DevAddr = DevAddr;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_NWK_SKEY;
                mibReq.Param.NwkSKey = NwkSKey;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_APP_SKEY;
                mibReq.Param.AppSKey = AppSKey;
                LoRaMacMibSetRequestConfirm( &mibReq );

                mibReq.Type = MIB_NETWORK_JOINED;
                mibReq.Param.IsNetworkJoined = true;
                LoRaMacMibSetRequestConfirm( &mibReq );

                DeviceState = DEVICE_STATE_SEND;
#endif
				printf("DEVICE_STATE_JOIN \r\n");
                break;

四、數據包類型
LoRaWAN規範中有不同的數據包，通過MType字段區分，MType是3位的，總共可以表示8種不同類型的數據，其中前六種是不同的數據包，分別是“入網請求”、“入網回覆”、“不需要確認上行數據包”、“需要確認上行數據包”、“不需要確認下行數據包”、“需要確認下行數據包”，後面兩個一個是預留（RFU），一個開放給用戶自定義（Proprietary）。

五、代碼整理

目前國內用的最多的就是sx1278,加上官網給的SDK增感覺不是很清晰，所以重新建立工程。代碼已經上傳到CSDN；硬件使用的安信可RHF76-052

由於目前手上沒有網關，所有調試代碼一直處於入網狀態中。官網代碼只是很簡單的例程，想要實際項目中使用還要修改很多東西，增加很多容錯機制。