Antenna switch never turns ON TX path on some SX1276 boards.

[branek]

During CE certification we are able to observe what we believe is the bug with antenna switch handling for some SX1276-boards.c implementations.

Our device uses B-L072Z-LRWAN1 as the reference.

In the function: void SX1276SetAntSw( uint8_t opMode ) there is no switching to TX path:

void SX1276SetAntSw( uint8_t opMode )
{
    uint8_t paConfig =  SX1276Read( REG_PACONFIG );
    switch( opMode )
    {
    case RFLR_OPMODE_TRANSMITTER:
        if( ( paConfig & RF_PACONFIG_PASELECT_PABOOST ) == RF_PACONFIG_PASELECT_PABOOST )
        {
            GpioWrite( &AntSwitchTxBoost, 1 );
        }
        else
        {
            GpioWrite( &AntSwitchTxRfo, 1 );
        }
        break;
    case RFLR_OPMODE_RECEIVER:
    case RFLR_OPMODE_RECEIVER_SINGLE:
    case RFLR_OPMODE_CAD:
    default:
        GpioWrite( &AntSwitchRx, 1 );
        break;
    }
}

There has to be call to GpioWrite( &AntSwitchRx, 0 ); function in case RFLR_OPMODE_TRANSMITTER: handling, before break statement for that case.

After we implemented the fix, we are able to see close to 19+ dBm CW power during conductive debug directly on antenna output (some losses because of measurement setup). Without the fix, power for 20 dBm CW setting is somewhere around ~16 dBm.