# Obstacle_Detection messages not appearing

Source: https://forum.modalai.com/topic/409/obstacle_detection-messages-not-appearing
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2021-08-21 00:48:54 UTC by Daniel Ryu
Replies: 16 · Views: 2374

## Daniel Ryu · 2021-08-21 00:48:54 UTC

Hello, I am trying to figure out how to turn on the collision prevention in voxl based systems, and despite following the linked instructions, I am unable to get Obstacle_Detection messages to appear in the QGC mavlink inspector. I enabled voa and voa messages to qgc, and configured the PX4 parameters using the given helper file. What should I try to receive Obstacle Detection messages?

 https://docs.modalai.com/voxl-vision-px4-collision-prevention/

## Reply by Daniel Ryu · 2021-08-24 21:31:09 UTC

I also calibrated the Stereo cameras and confirmed that output was coming out from the voxl-vision-px4 debug mode (-s flag)

## Reply by Daniel Ryu · 2021-08-24 21:34:15 UTC

![Screenshot from 2021-08-24 14-33-52.png](https://forum.modalai.com/assets/uploads/files/1629840854592-screenshot-from-2021-08-24-14-33-52.png)

## Reply by Guest · 2021-08-25 16:12:42 UTC

It looks like everything is set up properly, can you run ```voxl-inspect-cam dfs-disparity```and check to see that you're getting output there?

## Reply by Daniel Ryu · 2021-08-25 17:25:11 UTC (in reply to Guest)

@Alex-Gardner Doesn't seem like it, its stuck on this screen. ![Screenshot from 2021-08-25 10-23-50.png](https://forum.modalai.com/assets/uploads/files/1629912288119-screenshot-from-2021-08-25-10-23-50.png)

## Reply by Guest · 2021-08-25 17:30:43 UTC

can you do the same but with stereo: ```voxl-inspect-cam stereo```, if the dfs service is running and receiving frames it should be outputting data

## Reply by Daniel Ryu · 2021-08-25 17:36:00 UTC (in reply to Guest)

@Alex-Gardner I'm getting output just fine from stereo alone![Screenshot from 2021-08-25 10-35-32.png](https://forum.modalai.com/assets/uploads/files/1629912959216-screenshot-from-2021-08-25-10-35-32.png)

## Reply by Guest · 2021-08-25 17:40:17 UTC

What version of voxl suite/system image do you have? ```voxl-version``` should print this out

## Reply by Daniel Ryu · 2021-08-25 17:41:15 UTC (in reply to Guest)

@Alex-Gardner System image 3.3.0. Voxl-suite 0.4.6

## Reply by Guest · 2021-08-25 17:48:49 UTC

do you see dfs topics when you do ```ls /run/mpa```

## Reply by Guest · 2021-08-25 17:50:20 UTC

wait the name is dfs_disparity, not dfs-disparity, what does the inspect cam say with that ```voxl-inspect-cam dfs_disparity```

## Reply by Daniel Ryu · 2021-08-25 17:53:35 UTC (in reply to Guest)

@Alex-Gardner Output is generated for dfs_disparity ![Screenshot from 2021-08-25 10-53-01.png](https://forum.modalai.com/assets/uploads/files/1629914013749-screenshot-from-2021-08-25-10-53-01.png)

## Reply by Daniel Ryu · 2021-08-25 17:58:16 UTC

![Screenshot from 2021-08-25 10-57-35.png](https://forum.modalai.com/assets/uploads/files/1629914295135-screenshot-from-2021-08-25-10-57-35.png)

## Reply by Guest · 2021-08-25 18:43:24 UTC

The image is showing some disparity data there, the image is often very dark because it will be black if the dfs algo is unable to match regions and we do a lot of filtering to get rid of noise, but you can see 2 blobs there that it recognizes. If you're shoing the stereo cameras a blank wall or a repeating pattern it will be unable to properly match data.

## Reply by Daniel Ryu · 2021-08-25 20:30:06 UTC (in reply to Guest)

@Alex-Gardner That's good to know! How can I get the Obstacle Detection message to be sent to the QGC?

## Reply by Guest · 2021-08-25 21:14:23 UTC

the file at /etc/modalai/voxl-vision-px4.conf has settings for QGC IP, enabling VOA, and sending VOA to QGC. Make sure that the latter two are enabled and that your qgc ip is correct and it should send to QGC

## Reply by Daniel Ryu · 2021-08-25 21:36:49 UTC (in reply to Guest)

@Alex-Gardner That was it, the ip address was not inputted correctly. Thanks!