async fn write<T: HostToControllerPacket>(&self, val: &T) -> Result<(), Self::Error> {
            let mut buf: [u8; 259] = [0; 259];
            let w = WithIndicator::new(val);
            let len = w.size();
            w.write_hci(&mut buf[..])
                .map_err(|_| BleConnectorError::Unknown)?;
            send_hci(&buf[..len]);
            Ok(())
        }
Write a complete HCI packet from the tx buffer
esp-wifi/src/ble/controller/mod.rs