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
tried that with vmware on windows 8 but the wlan0 does not show up on ubuntu. I tried forcing the wifi adapter to automatically connect to vmware. But still no luck.
It should work fine. Try doing 'tail -f /var/log/syslog' when plugging it in and see what comes out. Also try rebooting the VM after putting the dongle in.
Thanks for the info, i will try it again.
I also added auto startup script for the transmitter to my google docs document for those who need it. Works perfectly.
making one for the receiving side now.
Finally got it working in vmware, details here:
https://docs.google.com/document/d/1avnqXqPOi_KwE6t1vfRaJDXWhRZP2C7...
After a ubuntu 14.04 lts update upgrade it suddenly just worked ;)
It shows the adapter using lsusb in ubuntu but it seems that the driver is not installed. When i reboot with blocking the vmware auto bridge functionality it shows in the boot screen that it can't download the ATH9K ... drive due to no ethernet connection. Now I'm trying to install it manually
Good to hear that you got it working :)
Happy to help - keep the money.
Paul
I have added the receiver image in my docs file, the transmitter will be done in 20 minutes.
My camera setup:
https://goo.gl/photos/ZgWBEHVdFtSqGucKA
3 axis GLB gimbal, latest stom32 firmware, fully controllable by pixhawk and via rc transmitter. Gopro Hero 3+ black with SRP ND4/CP filter, custom made housing to keep it steady on the gimbal bottom. It is not perfectly balanced but good enough.
Copter:
https://goo.gl/photos/fk6DY1GZDtZJe4RF9
Alien H4 680 antigravity 4006 cheapo 14x47 HK carbon props.
6S3P NCR18650PF Li-Ion cells, flight time 45-50 minutes with AOW of ~2.5Kg.
Need to move to bigger prop like 15 inch, as pixhawk calculated hover is ~64% now with all the added weight, but it flies fine with no tuning. Fast enough for video purposes and very stable. Going bigger than 15 inch would result in an significant overlap over the frame, so I would need to make up some mount to keep them further from the frame but still be fold-able.
There is also a guy on German ebay that sells hand made yagi's for wifi and fpv applications. Mine was like 20 euro incl. shipping and is compact, high quality and offers a gain of 13 dBi . Url: http://goo.gl/AcuHCg
I like the camera mount! I had a hell of a time trying to balance gimbals with the picam attached and I could never get rid of vibrations transmitted down the camera cable. I'm now trying to get uvc or hdmi from gopro/clone (sj4000 currently) to the raspberry instead - I found a nice floppy usb cable that shouldn't transmit vibes so will try uvc first.
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