Part 2: How to build a High-Definition FPV UAV using a Rasperry PI with HD camera, using a high speed WiFi link

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 192.168.1.2,  and for the ground station, 192.168.1.1.    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 = 192.168.1.1 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!

Views: 94017

Comment by Patrick Duffy on June 7, 2015 at 9:02am

@babak_ea, You don't necessarily need a high gain antenna on the UAV if you have a high-gain antenna on the ground mounted to a tracker.  Using a single high-gain antenna gives you both transmit and receive gain because the UAV will receive a stronger signal because of the directional pattern of the transmitted signal. The inverse is also true, as the weaker signal transmitted from the UAV is gained up by the high-gain antenna on the ground.   Of course, it would be an improvement to use two high-gain antennas, but that would require a tracker on the UAV, which is not very practical.   

Comment by babak_ea on June 7, 2015 at 9:25am

@ Bill Bonney

in the wifibroadcast project connection is unidirectional with use injection mode which not fully supported by most wifi chipsets , but seems at Patrick project used Bidirectional connection,so there is association between devices.
at the Bidirectional connection, I Think that for long range need good receiving at plane with high gain antenna .

(7 or 9 db omni antenna)

Comment by babak_ea on June 7, 2015 at 9:35am

@Patrick ,Thank you Patrick , Right

Comment by Fnoop on June 9, 2015 at 12:30pm

Hi Bill, this is probably the wrong thread to discuss this, but have you managed to connect apmplanner2 over wifibroadcast?

Comment by Dan Murray on June 27, 2015 at 1:35pm

Hey Patrick, would you mind posting your script to compile Gstreamer 1.4?

Thanks!

Comment by Patrick Duffy on June 28, 2015 at 5:36am

@Dan,  here it is.

#!/bin/bash

# Create a log file of the build as well as displaying the build on the tty as it runs
exec > >(tee build_gstreamer.log)
exec 2>&1

################# COMPILE GSTREAMER 1.4.5 ############

# Update and Upgrade the Pi, otherwise the build may fail due to inconsistencies

sudo apt-get update && sudo apt-get upgrade -y --force-yes

# Get the required libraries
sudo apt-get install -y --force-yes build-essential autotools-dev automake autoconf \
libtool autopoint libxml2-dev zlib1g-dev libglib2.0-dev \
pkg-config bison flex python git gtk-doc-tools libasound2-dev \
libgudev-1.0-dev libxt-dev libvorbis-dev libcdparanoia-dev \
libpango1.0-dev libtheora-dev libvisual-0.4-dev iso-codes \
libgtk-3-dev libraw1394-dev libiec61883-dev libavc1394-dev \
libv4l-dev libcairo2-dev libcaca-dev libspeex-dev libpng-dev \
libshout3-dev libjpeg-dev libaa1-dev libflac-dev libdv4-dev \
libtag1-dev libwavpack-dev libpulse-dev libsoup2.4-dev libbz2-dev \
libcdaudio-dev libdc1394-22-dev ladspa-sdk libass-dev \
libcurl4-gnutls-dev libdca-dev libdirac-dev libdvdnav-dev \
libexempi-dev libexif-dev libfaad-dev libgme-dev libgsm1-dev \
libiptcdata0-dev libkate-dev libmimic-dev libmms-dev \
libmodplug-dev libmpcdec-dev libofa0-dev libopus-dev \
librsvg2-dev librtmp-dev libschroedinger-dev libslv2-dev \
libsndfile1-dev libsoundtouch-dev libspandsp-dev libx11-dev \
libxvidcore-dev libzbar-dev libzvbi-dev liba52-0.7.4-dev \
libcdio-dev libdvdread-dev libmad0-dev libmp3lame-dev \
libmpeg2-4-dev libopencore-amrnb-dev libopencore-amrwb-dev \
libsidplay1-dev libtwolame-dev libx264-dev

cd $HOME
mkdir packages
cd packages
mkdir gstreamer-1.4.5
cd gstreamer-1.4.5

git clone git://cgit.freedesktop.org/gstreamer/gstreamer
git clone git://cgit.freedesktop.org/gstreamer/gst-plugins-base
git clone git://cgit.freedesktop.org/gstreamer/gst-plugins-good
git clone git://cgit.freedesktop.org/gstreamer/gst-plugins-bad
git clone git://cgit.freedesktop.org/gstreamer/gst-plugins-ugly
git clone git://cgit.freedesktop.org/gstreamer/gst-libav
git clone git://cgit.freedesktop.org/gstreamer/gst-omx

cd gstreamer
git checkout -t origin/1.4
./autogen.sh
make
sudo make install
cd ..

cd gst-plugins-base
git checkout -t origin/1.4
./autogen.sh
make
sudo make install
cd ..

cd gst-plugins-good
git checkout -t origin/1.4
./autogen.sh
make
sudo make install
cd ..

cd gst-plugins-ugly
git checkout -t origin/1.4
./autogen.sh
make
sudo make install
cd ..

cd gst-libav
git checkout -t origin/1.4
./autogen.sh
make
sudo make install
cd ..

# Install libusb-1.0 to enable uvch264src
sudo apt-get install -y --force-yes libusb-1.0

cd gst-plugins-bad
git checkout -t origin/1.4
export LD_LIBRARY_PATH=/usr/local/lib/ path
sudo LDFLAGS='-L/opt/vc/lib' CPPFLAGS='-I/opt/vc/include -I/opt/vc/include/interface/vcos/pthreads -I/opt/vc/include/interface/vmcs_host/linux' ./autogen.sh
make CFLAGS+="-Wno-error"
sudo make install
cd ..

cd gst-omx
LDFLAGS='-L/opt/vc/lib' CPPFLAGS='-I/opt/vc/include -I/opt/vc/include/IL -I/opt/vc/include/interface/vcos/pthreads -I/opt/vc/include/interface/vmcs_host/linux' ./autogen.sh --with-omx-target=rpi
make CFLAGS+="-Wno-error"
sudo make install

Comment by Dan Murray on June 29, 2015 at 9:29am

@Patrick, thank you!

Have you tried on an RPi2 yet? Converted my setup over to the 2, seem to be getting more pixelation than I remember.

Comment by Patrick Duffy on July 13, 2015 at 3:23pm

@Dan,  sorry for the late response. I have been hiking the mountains of New Mexico for the last two weeks. 

I have the RPI2 on a hex copter and I have not noticed any change in pixelation. Are you using the same GStreamer version and pipeline?

Comment by babak_ea on July 18, 2015 at 2:08pm

Hi Patrick Duffy
in this post that you link above there is some changes:
1- Set the host name...
2- Memory split...
3- Enable SSH ...
do need this changes in your project ?
sorry for my bad English.

Comment by Patrick Duffy on July 18, 2015 at 9:30pm

Hello @babak_ea,   The items you listed are part of the PI setup. You should at least give enough memory to the GPU to use the camera with compression.  Enabling SSH is optional, but I always enable it so I can remote shell into the PI. 

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