After much chasing, and testing, I have found this to be an efficient way of getting low latency high quality HD video out of an Aircraft. The latency is around 0.4 seconds at worst which would be OK for an FPV with an APM doing the hard work.
I will continue to search for methods to drop the latency down further, but this is a lot better than the 6-12 seconds I was getting on my first attempts.
Any comment (with useful instructions) would be appreciated.
For the wireless link, I am using two UBIQUITY ROCKET M 900 with Australian ACMA approved firmware, at the base station, I am using a tracking (yet to built the tracker...) 1.5 meter long X and Y polarised Yagi, and on the plane, two RF Design flexible strip antennas, placed at right angles to each other.
but how you do that bit is up to you.....
the critical bit is getting the Raspberry Pi's to chat to each other.
I have tried to make this as user friendly as possible... good luck.
Setting up IP video for Raspberry Pi 1080p video (FPV)
You will need 2 B model Raspberry Pi's and 1 Pi Camera. (Element 14, or RS components)
Preparing your Raspberry Pi for first boot…
Follow the instructions at http://www.raspberrypi.org/wp-content/uploads/2012/04/quick-start-guide-v2_1.pdf
Install the prepared SD card in the Pi and boot.
Setting up your Pi
Connect the Pi to your router with a network cable.
On Start-up it will resize the FAT partition and present you with a menu.
Set your language, and keyboard layout.
Select Raspbian… then click install.
After this has extracted (will take a while….) it will reboot into the configuration screen (again will take a while for this first boot.)
The important things to change here are
- Enable the camera
- In advance options…..
- Set the host name (camera, for the camera end, receiver, for the viewing end)
- Memory split, set the memory for the GPU to 256
- Enable SSH ( will come in handy later, as you may need to talk to the Pi in the air.....
Then finish and reboot.
First login
Username: pi
Password: raspberry
Setting up the required programs for video streaming
Install the dependencies by running the following in a terminal:
sudo apt-get install mplayer netcat
cd /opt/vc/src/hello_pi
make –C libs/ilclient
make –C libs/vgfont
cd /opt/vc/src/hello_pi/hello_video
make
cd ~
Now repeat this for the other Pi….
Streaming…
First set up the receiver….
Ensure the receiver is connected to your network and run
ifconfig
after you press enter, you can find your ip Address. Note this down.
Then run the following.
mkfifo buffer
nc -p 5001 -l > buffer | /opt/vc/src/hello_pi/hello_video/hello_video.bin buffer
the Pi will now wait for the feed.
On the Camera Pi
Ensure camera is connected to the Pi
Ensure Pi is connected to the network (you can confirm this with ifconfig)
(see instructions at http://www.raspberrypi.org/camera for how to connect the camera)
In the following command, replace the ip address with the one you just noted down.
raspivid -t 0 -fps 15 -o - | nc 192.168.1.85 5001
if all goes well you should be streaming 1080P video at 15fps with less than 0.5seconds of delay..
now add your wireless bridge between the two, and away you go J
This information has come from the Raspberry Pi foundation website, and other sources, tested and proven by myself..
Comments
I see on the 3DR documentation that the 3DR radio's CTC is connected on the APM 2.5 and on the APM 2.0 it is not, did you only connect the tx and rx or did you connect the CTC as well?
I don't use a level converter. Just a direct connection. I know there is a 3.3 vs. 5 volt difference, but i took a chance and it's been working perfect for a long time :)
Where is your logic level converter or did you put it on its own 3.3v?
On the Rpi there is a pin row like this. Pins 6,8 and 10(Ground, TX and Rx) must be connected to the corresponding pins in the Telemetry port at the APM. Cable 1, 3 and 4 from the edge of the APM. (Ground, TX and Rx)
Draw a picture for us noobs please.
Why make it som complicated!? I just connected 2 cables directly from the Telemetry port to the UART (/dev/ttyAMA0) in the Raspberry Pi and installed "ser2net", thats all you need!
I think I'll look into ser2net and remtty. Just found socat. http://www.raspberrypi.org/phpBB3/viewtopic.php?t=44896&p=356396 - used for video here but could also just mirror the serial output. I'll run some tests with htop. Philip - when running your tests did you kill the gui? Usually fairly major performance improvements on most 'nixs. Family here for Canadian thanksgiving so no time for testing yet.
http://diydrones.com/group/telemetry-over-cellular-ip/page/testing-... for the widows nission planner side. And while I'm throwing wild ideas about - gstreamer supports overlay's - so an apm telemetry stream on the hd display should be possible just by tee'ing the output - http://wiki.oz9aec.net/index.php/Gstreamer_cheat_sheet. So another week with no sleep.
I have found the answer
http://www.andremiller.net/content/raspberry-pi-and-arduino-via-gpi...
If someone does a tidy job of this please let me know
Have a look at this youtube video
For those wondering what's inside a nano 900 I took one apart - http://imgur.com/Ddz3Z3S,2pbJNfp#0 Not that big for a guestimated 12 km range (HD).. Make some attenuators for the two internal antenna ports - and add the aforementioned circular antenna. Will try out this week.
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