Hi
Over the last couple of months I have been working on a project that might be of interest to you: https://befinitiv.wordpress.com/wifibroadcast-analog-like-transmission-of-live-video-data/
Basically it is a digital transmission of video data that mimics the (advantageous) properties of an analog link. Although I use cheap WIFI dongles this is not one of the many "I took a raspberry and transmitted my video over WIFI"-projects.
The difference is that I use the cards in injection mode. This allows to send and receive arbitrary WIFI packets. What advantages does this give?
- No association: A receiver always receives data as long as he is in range
- Unidirectional data flow: Normal WIFI uses acknowledgement frames and thus requires a two-way communication channel. Using my project gives the possibility to have an asymmetrical link (->different antenna types for RX and TX)
- Error tolerant: Normal WIFI throws away erroneous frames although they could have contained usable data. My project uses every data it gets.
For FPV usage this means:
- No stalling image feeds as with the other WIFI FPV projects
- No risk of disassociation (which equals to blindness)
- Graceful degradation of camera image instead of stalling (or worse: disassociation) when you are getting out of range
The project is still beta but already usable. On the TX and RX side you can use any linux machine you like. I use on both sides Raspberrys which works just fine. I also ported the whole stack to Android. If I have bystanders I just give them my tablet for joining the FPV fun :)
Using this system I was able to archive a range of 3km without any antenna tracking stuff. At that distance there was still enough power for some more km. But my line of sight was limited to 3km...
In the end, what does it cost? Not much. You just need:
2x Raspberry A+
2x 8€ wifi dongles
1x Raspberry camera
1x Some kind of cheap display
Happy to hear your thoughts/rebuild reports :)
See you,
befinitiv.
Replies
I've ordered a couple of RPi2 boards, an RPi camera and the TP-LINK TL-WN722N and Alfa AWUS036NHA wifi adapters so I hope to recreate what befinitiv has done and report back. Hopefully the RPi2 will also work ok, maybe an ODroid W would also work and it's quite small.
I hope all of us on this thread can share info and experiences so we can push forward more painlessly.
The idea of providing an image that people can burn onto their RPi boards is a good step I think in making the setup easier.
Randy, the AWUS036NHA model is 5.8ghz also ??
I'm using RPI2s with no problem (same dongles)... I don't see any massive improvements compared to what befinitiv has documented. I saw openfpv moved from rpi to Odroids but haven't seen any updates on that project in a long time.
There are multiple revision of WN822 with different chipset
v1 use atheros AR9170 and AR9102
v2 use atheros AR7010 and AR9287
v3 use RTL8192CU
i know that the chipset in v3, RTL8192CU, is very problematic under linux, need a kernel patch i think.
AR9170 should work in monitor mode, based on the info i've found on the backtrack 5 forum (B5 is a security linux distro)
bye
This is a really cool project with potentially huge impact. There's really no open source readily available wifi video system out there. This is worthy of a front page blog post or even a kickstarter.
Update: I added software diversity to the project which greatly improved reception quality: https://befinitiv.wordpress.com/2015/05/24/diversity-for-wifibroadc...
I am having a hard time deciding what to get, a WN722 or WN822... but I am more inclined to go for the 822.
The reasons:
I don't need to go that far (to 3KM), 200 to 500 meters is more than enough for me.
The problem is that the transmitter that I use for my custom made drone (3D printed) is a Turnigy 9x, so it will probably interfere with the WiFi, This is why I am thinking to make my own "transmitter" / controls, that interface with the Raspberry Pi, and have the Raspberry Pi send the controls information to the receiver (the drone). This means that I can't use broadcast since I need 2 way transmission. This also allows me to have many more features, like "follow me" because I can send my current GPS coordinates to the drone. This also means that I can send an almost infinite amount of commands/channels (unlike the 8 channels I get with my Turnigy 9x).
Also, I can send live way points for it to follow.
I have a 3D printer, and I can design the drone with compartments to house all the electronics. Right now I am using a Naze32 flight controller on my 3D printed quad, and I am thinking to connect the Naze32 to the Raspberry Pi, so that the Raspberry Pi will act as the receiver. Then, the Raspberry Pi won't have to deal with the actual flight, but it will be the "brains" on what to do when something happens. For example loss of signal, it can return to home in a straight line, or I can set it to return home following the exact path it took to get there...
Since WN822 supports diversity I can get better range while still using regular 2 way WiFi.
I am a computer programmer, and I also worked with microcontrollers before (I also know a little bit of electronics), so I am sure I can figure it out. The new part for me is that I never made a program for Linux (related), I only developped on Windows before (and PIC microcontrollers). Hopefully google will help when I am stuck on Linux problems :)
All the above... while receiving live HD quality video, that is going to be awesome !!
This week I will go get a second Raspberry Pi 2, and the camera for it. Hopefully I will be able to put my theories to test sometime soon :)
The biggest problem for me is finding the time to work on this.
It would be great if you could test the WN822 to see if it supports monitor mode for the rest of us. It would be great to have a dual antenna output on the vehicle end since there is almost always a blind side with a single antenna.
Hi befinitiv,
I found at my local computer store the WiFi WN722N and they also have the WN822N (at 300Mbps, and only $3 more than the 722).
Do you think I can do the same thing with the WN822N ? with possibly improved performance?
The WN822N uses a different chip than the WN722N. It seems as if the 822 support diversity which might be an advantage. But the risk of using an unknown chipset is quite high. It is likely that it won't be compatible with wifibroadcast.
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