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.
@Jerry, which antenna are you planning on using? A high-gain dish will have a very narrow beam so your tracker has to be very accurate, plus the elements are linear polarized. Also what antennas are you using on the remote? Skew-Planer-Wheel or ?? If you are using a circularly polarized antenna on the remote, you will get a 3-db loss to your dish, however if the dish is much higher gain, and you can track it, then the extra gain on the dish will be worth using a parabolic. I tried this setup, but could not get the tracker to stay within the beam of the antenna so I abandoned the dish in favor of a lower gain and wider beam-width helical.
@Patrick I had the first running Yocoto script build for rt-linux patched distro, i will test function and clean up the code, meanwhile waiting for my first pair of nanobeam m5 delivery.
building an antenna will be very tricky on some details. getFPV helix antenna has the requency range of 5600-5980Mhz, but gain is not higher than an ubnt dish...so i don't want to try buy on and then extending the rounds. maybe try it later with a proper reason.
@Gavin I am designing a 3D printing + carbon tube + IPX foam version glider, i'll model it in solidworks. it will use a 20mm diameter carbon tube at fuselage and 4*18650 3C batteries inside, i guess. Mounting nanobeam underneath the main tubing, grass landing may be ok. I dont have any prior experience, so this will be a total failure from selecting components. I will use gear for the motor and configuration like XUAV-one.
Ardusora sensor is the prerequisite of trying this branch? i will have a look into it and get the sensor.i hope i could make a apm auto build script based on Yocoto, still doing by learning. Emlid Navio is not open sourced hardware, and out of stock. Building new board design will be time consuming... so i have to use apm + rpi this time.
If possible, where we setup a github project or a wiki site to begin this project?
@Jerry, I have posted the source code on GitHub. Just search for GStreamerHUD. I don't have build instructions yet, but eventually I'll get that done.
For the antenna setup, I have access to the most advanced test chambers in the world for testing antennas, as I work for a wireless company that tests cell phone antennas, tower base stations and fixed antennas for both SISO and MIMO. I will be posting some data on the helical 5.8ghz models from IBCrazy and from Circular Wireless in a few days as soon as I can get some chamber time to try it out.
Your idea of making one with a PVC pipe is ok. I would take a look at the model that IBCrazy is selling, as it's just a plastic tee with grooves cut in 1cm spaces, which is good for the 5.8ghz range. Pretty easy to home build if you don't want to pay the $50.
I'd make a new thread. I would have lots to contribute seeing how I have many tall towers at my disposal and my 3.65 license. I would like to do a test where the aircraft hops to and from multiple ground stations.
@Gavin I've been pulling hair for a week to build a custom RPi distro for FPV, on yocto. My Wi-Fi testing will begin after i have sort this out. Maybe i'll try FreeBSD TDMA Atheros driver first, it's a simple airMax and open source, but outdated for hardware generation.
@Patrick I have read your other blogs, maybe i want to build my own antenna, i have done some helix with PVC pipes before, but i don't have enough knowledge to design them from start. and i don't have RF instruments for testing. so i need to source some designs for this application. Your Qt Gtreamer program i have tested, very nice, good job. if you wish to share the source code it will be very appreciated. And i will try Android version later.
It's off the topic to talk about "poor man's" version of facebook's airborne internet relay system here. if you are interested we can setup a thread for this.
i don't have experience with fixedwings, i'm very interested in DLG making and looking for building and fly it.
My glider has apm 2.6 amazon neewer brand Im using 5.8 fatshark for video for now
@Gavin, so your glider has a raspberry pi or ?? I have one of these, but no video link:
Ardusoar looks interesting. Let me know how it turns out, I may buy a controller for my glider.
Here is the link to overview. Looks like the radian pro is going to get the WiFi treatment soon. Probably 900 mhz.
Very nice! I like the glider satellite idea very much and found something that would be amazing to couple with this technology. Behold, http://diydrones.com/profiles/blogs/thermopilot-project-a-thermal-h...
@Jerry, Here's a link to the antenna I am using with my Rocket M5:
They don't sell a LHCP version, so I purchased two, and re-wound one of them to be LHCP. It took a bit of soldering but it's pretty easy. I mounted them on my M5 with a home-built antenna tracker. Here's a photo:
I have another blog on how to build the tracker. For the UAV antennas, I used a pair of these:
I purchased a LHCP version direct from the manufacture. You have to send them an email and ask for a special order to get one of these LHCP. With this setup, you can enable the 'AirMax' protocol (MIMO/TDMA).