def send_rpc_async(self, conn_id, address, rpc_id, payload, timeout, callback):
        """Asynchronously send an RPC to this IOTile device

        Args:
            conn_id (int): A unique identifer that will refer to this connection
            address (int): the addres of the tile that we wish to send the RPC to
            rpc_id (int): the 16-bit id of the RPC we want to call
            payload (bytearray): the payload of the command
            timeout (float): the number of seconds to wait for the RPC to execute
            callback (callable): A callback for when we have finished the RPC.  The callback will be called as"
                callback(connection_id, adapter_id, success, failure_reason, status, payload)
                'connection_id': the connection id
                'adapter_id': this adapter's id
                'success': a bool indicating whether we received a response to our attempted RPC
                'failure_reason': a string with the reason for the failure if success == False
                'status': the one byte status code returned for the RPC if success == True else None
                'payload': a bytearray with the payload returned by RPC if success == True else None
        """

        found_handle = None
        # Find the handle by connection id
        for handle, conn in self._connections.items():
            if conn['connection_id'] == conn_id:
                found_handle = handle

        if found_handle is None:
            callback(conn_id, self.id, False, 'Invalid connection_id', None, None)
            return

        services = self._connections[found_handle]['services']

        self._command_task.async_command(['_send_rpc', found_handle, services, address, rpc_id, payload, timeout], self._send_rpc_finished,
                                         {'connection_id': conn_id, 'handle': found_handle,
                                          'callback': callback})