# mavros node on base station fcu_url

Source: https://forum.modalai.com/topic/50/mavros-node-on-base-station-fcu_url
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2020-12-01 15:27:08 UTC by rapit
Replies: 4 · Views: 2784

## rapit · 2020-12-01 15:27:08 UTC

Hi,
I usually connect my QGroundControl (running on base station) to the voxl which in my unsderstanding "routes" the mavlink data from the flight core to my base station.

Sometimes I want to run a mavros instance not on the voxl but on my base station. I am not sure how to configure this node correctly in order to connect to the flight core using voxl as "wifi link". It works if I set the `fcu_url` param like that: `udp://:14550:@VOXL_IP:14556` but then the link in my QGroundControl fails. I guess it is because both connections are running over port `14550`. I have no idea how to set `fcu_url` and gcs_url`. Or do I have to install additional software on the voxl to route the packages?

Any help would be appreciated!

## Reply by Chad Sweet (ModalAI staff) · 2020-12-01 15:40:05 UTC

Hi Rapit, have you looked at this doc [here](https://docs.modalai.com/voxl-vision-px4-telemetry/)?

I think you'll want to look at this parameter "en_secondary_qgc"

## Reply by rapit · 2020-12-01 15:57:39 UTC

Hi Chad,
thank you for the link. I did read section before but I could't see how it would help me as the port on the outgoing connection is still the same.

I just configured my base station ip in `ggc_ip` and `secondary_qgc_ip` (and `en_secondary_qgc`) and the connection to my ground control station is successfully initiated by voxl. But when I fire up mavros at my ground station, QGroundControl again loses the connection to voxl, so initiating "from the other direction" does not seem to solve the port conflict.

## Reply by James Strawson (ModalAI staff) · 2020-12-01 20:12:43 UTC

Hi Rapit,

You don't need the secondary qgc_ip, just one udp link from VOXL to MAVROS. In this case you would use MAVROS as another link in the chain between VOXL and QGC.

VOXL <--> MAVROS <--> QGC

Try launching mavros with the fcu_url :
fcu_url:=udp://VOXL_IP:14550@:14550

and gcs_url:
gcs_url:=udp://@127.0.0.1

You may need to change the port to QGC to something else (like 14551) to avoid a conflict.

Best,
James

## Reply by rapit · 2020-12-02 13:38:23 UTC

Thank you, it works now. I did not think about using my local mavros as connection link between voxl and QGroundControl.

I changed the port. The original issue was a binary installed mavros which crashed when using a `gcs_url`. So I thought it was a configuration problem but building mavros from source and running with your proposed configuration worked. Thank you again!

Raphael