STM32WL store NVM context Lorawan

[RPaja.1]

Hi,

I need some help trying to undestand this operation in Lorawan_end_node example project

nvm_size = ( ( sizeof( LoRaMacNvmData_t ) + 7 ) & ~0x07 ); in the code below:

Maybe it is so simple, but i thought that it would be something like that

nvm_size = sizeof( LoRaMacNvmData_t );

Thanks in advance

LmHandlerErrorStatus_t LmHandlerNvmDataStore( void )
{
#if (defined( CONTEXT_MANAGEMENT_ENABLED ) && ( CONTEXT_MANAGEMENT_ENABLED == 1 ))
    LoRaMacNvmData_t *nvm;
    uint32_t nvm_size;
    LmHandlerErrorStatus_t lmhStatus = LORAMAC_HANDLER_SUCCESS;
    int32_t status = NVM_DATA_OK;
 
    lmhStatus = LmHandlerHalt();
 
    if( lmhStatus == LORAMAC_HANDLER_SUCCESS )
    {
        status = NvmDataMgmtStoreBegin();
 
        if( status == NVM_DATA_NO_UPDATED_DATA )
        {
            lmhStatus = LORAMAC_HANDLER_NVM_DATA_UP_TO_DATE;
        }
        else if( ( status != NVM_DATA_OK ) || ( LmHandlerCallbacks->OnStoreContextRequest == NULL ) )
        {
            lmhStatus = LORAMAC_HANDLER_ERROR;
        }
        else
        {
            MibRequestConfirm_t mibReq;
            mibReq.Type = MIB_NVM_CTXS;
            LoRaMacMibGetRequestConfirm( &mibReq );
            nvm = ( LoRaMacNvmData_t * )mibReq.Param.Contexts;
            nvm_size = ( ( sizeof( LoRaMacNvmData_t ) + 7 ) & ~0x07 );
            LmHandlerCallbacks->OnStoreContextRequest( nvm, nvm_size );
        }
 
        if( NvmDataMgmtStoreEnd() != NVM_DATA_OK )
        {
            lmhStatus = LORAMAC_HANDLER_ERROR;
        }
    }
 
    if( ( lmhStatus == LORAMAC_HANDLER_SUCCESS ) && ( LmHandlerCallbacks->OnNvmDataChange != NULL ) )
    {
        LmHandlerCallbacks->OnNvmDataChange( LORAMAC_HANDLER_NVM_STORE );
    }
 
    return lmhStatus;
#else
    return LORAMAC_HANDLER_ERROR;
#endif /* CONTEXT_MANAGEMENT_ENABLED */
}

[IIRHO.1 · Accepted solution]

Hello @RPaja.1​  ​ and welcome to ST Community

I think that this line of code is used in order to round the size of the `LoRaMacNvmData_t` to the nearest multiple of 8 bytes.

hope this is helpful

Issam

[RPaja.1]

Thanks for your response @IIRHO.1​ , sizeof returns the number of bytes of LoRaMacNvmData_t, in that case 1484 bytes, is it correct?

It is multiple of 8 bits, my operation, maybe is wrong is that:

nvm_size = ( ( sizeof( LoRaMacNvmData_t ) + 7 ) & ~0x07 );

nvm_size = ( ( 1484 + 7 ) & ~0x07 )

nvm_size = (1491 ) & 0xFFF8 )

nvm_size =1488

Do you mean multiple of 8 bytes?

[IIRHO.1]

Hi again @RPaja.1​  yes, I mean 8 Bytes . It's just a typo. I corrected . If this is what you are looking for, please mention my answer as the best answer so that the information will be defused