Part Two: Here is the original picture of the finished product:


This is the second part of a 2-part series on 'How to build a High-Definition FPV UAV using a Raspberry PI with HD camera, using a high speed WiFi link.

In my first post on the subject (located here), I discussed the parts I used, and how to install them into a Hobby King Go-Discover FPV model. 

In this post, I will discuss installing the Raspberry PI and the PI camera in the Go-Discover gimbals, and the software configuration for both the Raspberry PI and the ground station PC.

From the previous post, step 3 was completed by installing the Ubiquity Rocket M5 in the model.  Now onto step 4:

Step 4: Install the Raspberry PI and PI Camera

Here is a photo of the position of the PI in the Go-Discover model:


The PI fits nicely just behind the camera gimbals, with the USB and HDMI ports on top. In the right side you can see the Cat5 network cable attached. This cable connects to the ethernet switch, which is also connected to the Rocket M5 input port.  

The two cables shown on top are the servo control wires for the gimbals, which I have directly connected to channel 4 and 5 on my radio.  I am using channel 4 (normally the rudder stick on my radio. Since there is no rudder on a flying wing, this is a convenient channel to use to move left and right with the camera. I have not (yet) moved to a head tracker, but if you already have that setup, just assign the channels accordingly.

To install the PI camera, remove the stock plate from the gimbals (for a GoPro), and mount the PI camera as shown in this photo:


The PI camera case fits very nicely into the slot, and again I used a small piece of velcro to hold it down. You could use a couple of small screws instead if you want a more secure hold.  The two gimbals servos are also shown here. They are simple to install, just follow the Go-Discover instructions.

Here is a front view of the PI camera installed:


Here is the block diagram describing all the connections:


Some comments on my previous post suggested that it is possible to eliminate the ethernet switch and serial-to-ethernet converter using the Raspberry PI and a serial port on the PI. I believe this post describes how to talk to the PI via the NavLink, but in this case, I want to use the PI to bridge the connection from the ground station to the APM/PixHawk. Somebody please comment on this if you know more about it.   I believe it would require a TCP/IP to serial link from the PI to the telemetry port on the APM, and some software on the PI to act as the bridge.  The main connection to the ground station is via the Rocket M5 and TCP/IP, not through a telemetry link (900 Mhz or Zigbee like I used on my other models).

Step 5: Getting it all to work with software configuration (the really fun part starts now).

Check out this post on what others have done with streaming and the PI.  My experiments showed that using GStreamer on both the PI and on Windows gives really good results with very low latency, if you use the right parameters. 

Get GStreamer on the PI by following this blog.   This is the same version of GStreamer that I am using on my setup. 

Make sure your PI camera works ok by plugging in the PI to a standard monitor using the HDMI port and follow the instructions on the Raspberry PI website on how to get the camera up and running (without GStreamer).  Once you have a working PI and camera, you can then proceed to stream things over the network.  

Note: It is suggested that you first get the PI streaming video by plugging it directly into your local network where you can also connect your ground station PC with the correct IP addresses (without the Rocket M5).   For my PI, I picked,  and for the ground station,    Make sure you can ping the PI from your PC and the PC from the PI.  

For streaming, you will also have to make sure all the ports you intent to use are open on the firewall (described later).

For the ground station PC,  you can download GStreamer here.  Make sure when you install, select to install everything , or full installation (not the default). 

Here is the command I use for the PI to pipe the camera output to GStreamer:

raspivid -t 0 -w 1280 -h 720 -fps 30 -b 1700000 -o - | gst-launch1.0 -v fdsrc ! h264parse config-interval=1 ! rtph264pay ! udpsink host = port= 9000

The command is explained as follows:

raspivid is the command to start the camera capture on the PI.  The -w switch is for the width in pixels, and the -h switch is for the height.  In this case, I am using 1280 X 720, but you can try any combination that fits your needs. 

The -b switch is the bit rate for the sampling. In this case I chose 1.7mbs to send over the stream. Again you can experiment with higher or lower values. This settings seems to work good for me, and the latency is almost unnoticeable.  

the "-o - |" is piping the output to gstreamer.  Make sure you include the dash before the pipe "|" symbol. 

For the GStreamer command, all the filters are separated with an exclamation point "!", as these are individual drivers that are part of GStreamer.  Since the PI has hardware accelerated video, the output is in a format called "H264", which is a highly-compressed stream. The GStreamer filters are configured to transport the output via a UDP socket connection to the target PC. Notice the 'udpsink' element which specifies the host - in this case your ground station, and the UDP port.  I am using port 9000, but you can use any open port on your system, but be sure to open the firewall or it won't work!  You can also use TCP instead of UDP, but for such a data stream, I chose to use UDP since dropouts are certainly possible, and with UDP this is ok, but with TCP, you could have socket problems and higher latency. 

Note: to get the PI to execute this command on boot, make a shell script with the above command and add it to your local.rc boot sequence. That way when the PI boots, you get the stream without having to log into the PI remotely. 

For the ground station PC, once you have installed GStreamer and opened the correct ports, use this command (from the command prompt) to view the stream:

c:\gstreamer\1.0\x86_64\bin\gst-launch-1.0 udpsrc port=9000 ! application/x-rtp,encoding-name=H264,payload=96 ! rtph264depay ! avdec_h264 ! videoconvert ! autovideosink

If all goes well, you should see the PI camera output on your PC screen in a popup window.  For those of you what want to use FPV goggles, you can connect to the HDMI port on your PC to display the output if your goggles support HDMI. 

I have this command in a batch file (with a PAUSE) statement at the end to keep the window open.

WHEW!  If you got this far, you are amazing. 

The last step to complete the build is to connect to the APM from mission planner.  The method I used to connect was to install a utility that converts a TCP connection to a virtual serial port, but I also think that directly connecting the mission planner to the TCP port will also work, however I have not tried it. I will post back later after trying it.

Here is the link to setup the serial to ethernet device to have an IP address and port.

Here is the link to the configuration utility for installing the virtual serial port.   

Once you have a serial connection over TCP/IP working to the APM, you should be able to connect with Mission Planner. On the maiden flight, it worked perfectly, and I didn't see a single drop in the telemetry data or anything noticeable in the video transmission, however my first flight was limited to 2km.

The last step is to connect the Rocket M5 to the Nano M5 and test everything using the OTA (over the air) connection. If all is well, you are ready to fly!  But be careful on your maiden, you just spent $700. 

Finally, here is a photo of my Antenna Tracker with the Nano M5 attached. My next update will include a video of a longer flight.  


Happy Flying!

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  • Got my Odroid-w today. With the usb/ethernet the weight of the raspberry and the Odroid-w is about the same. The Odroid-w with cape weights 40 grams and the raspberry 42 grams. Since we dont need all the usb ports maybe a usb ethernet module can be used and save some weight.


  • @Aleksander, my OSD prototype is here I plan to port it to QT5 & Gstreamer 1.2, write GUI, where you can customize the HUD and Gstreamer pipeline and write a complete guide how to connect it to Pixhawk or APM via Raspberry till the end of this month.

  • @Aleksander, I have a prototype for the HUD working with Qt and APM Planner 2.0.   I was thinking of a way to do this using GStreamer, and I found a QtGStreamer library that allows you to overlay a QtWidget with a GStreamer video source.  Currently APM Planner hides this screen by default, but I downloaded the source and built a custom version. The drawback now is the antenna tracker is not yet available in APM Planner, and needs some work.  

  • Finally went with the Wispstation M5 and a Rocket M5.

    I just couldn't see my self succeeding resoldering a groove or a bullet with one iron in each hand, one in each foot and a fifth in my mouth without getting some serious burn injuries :) (Germany) had the Wispstation for almost the same price.

  • @Justin - wow that's dedicated :)

    @Nils - yes I must have!  Unfortunately it looks like it's a 'legacy' product, I'll try and find out if they have a similar replacement.

    @Patrick - yes I'm planning to connect the pi straight to the pixhawk and run mavproxy to get bidirectional control over the wifi link.  This way I'm hoping to remove the need for the dedicated 433/900 telemetry radios, thus further removing weight.

    @Steve - wispstation connector is the tiny ufl connector.  I bought a £3 ufl->sma convertor from amazon to connect the spironet atenna.  It's a single antenna - I didn't want the weight or expense of the MIMO setup.

  • @Steve, I'm using STX-HG5 (GND) and STX-5HnD (SKY) in short range (manual tracking). For longer ranges I use "vibrator" ("groove") in GND setup connected to 30dB parabolic dish. Haven't tried flying the "vibrator" cause its antenna mount with omni antenna itself exceeds STX's weight greatly (SXT w/o enclosure is 100+ g).
    FYI - here's a list of Mikrotik's distributors:
    I've purchased my STX's from "Inter Projekt S.A." (they're in Poland as far as I can recall). 

  • Also Dom for the Wispstation how do you connect antennae to it? I saw pic of it and I don't quite see how you connect antennae to it? If so is it singular antenna or multiple?

  • I think you could just use mission planner? I know they added the ability through I believe gstreamer for you to replace the generic blue-green background in the HUD with actual video overlay. I've done this with analog I imagine it would be similar with this too.

  • Does anybody have an idea on how we could implement an OSD into this system?
  • @Dom,  The Go-Discover rig I built is about 4.5 lbs and it all just fits. No problem flying at that weight for a flying wing, but not for a quad. For your application, it appears size/weight is much more a premium. You can get rid of the ethernet switch I used, and connect your controller directly to the PI. and t he Serial-To-Ethernet converter also disappears, and the extra battery can also be ditched to save weight. I have not yet made this modification to my setup, but I plan to try it as soon as I can get the software working on the PI for telemetry. 

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