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 have the BM5 here so I wanted to test with them, I would strip it down removing the housing. Adding, N female to SMA female adapter would only be about 65 grams total. On my hexa or big quads it would hardly be noticed. POE direct to the board is also really easy too, with the onboard regulator so no fear as the Raspi is powered separately and not through the ETH0
As for the ground station I have a Mobile Command Post with onboard 220/110 vac
I would like to test this but need a bit of help with the scripts to try it for SAR operations
Thanks
Lol well yes more suitable then :) Really cool setup. I did take a quick look around the other day and it looks like Ubiquiti are refusing to make any effort to support monitor mode though. Are you saying it can be driven directly somehow by the raspberry?
ps - the ubiquiti devices have onboard power regulators so you can fire lipo 3s/4s power straight down the poe injector which is quite nice. I did make sure it wasn't going anywhere near the raspberry, I don't think that's what was blowing them.
A couple of people have measured the latency of their system very accurately so to save some people some effort I'd like to show the procedure that Jaime used to measure the "lense to screen" latency on his system (which is actually using regular point-to-point wifi but the same procedure works for any system).
What you do is:
1. on the ground station computer (RPi, Ubuntu, Mac, etc) pull up estopwatch.net and click the start button
2. point the vehicle camera at the ground station computer's screen. This should produce an endless image within image tunnel.
3. do a screen capture on the ground station computer
4. the latency is the time difference between any two consecutive times. So in the image below it's 52.885 - 52.707 = 0.178 seconds (or 178ms).
Missed this, apologies. I only tried them in 2.4G but they worked fine. I did pick up the adapters befinitiv recommended since he'd done the work on patching their kernels and I wanted to minimise differences from the base platform.
I'm wondering whether RPi 2 is capable of running Mission Planner.
Meanwhile I stumbled upon this GCS --> https://github.com/multigcs/multigcs
What's about the latency?
It runs APMPlanner2, if that helps. I always had very unsatisfactory results running MP under wine, even on a reasonably powerful desktop.
MP runs natively under Linux. No need to use wine.
Just for information, on this page a found this:
Toshiba HDMI to MIPI CSI2 bridge chip TC358743XBG
http://blog.pi3g.com/2014/03/embedded-world-in-nuremberg-2014-new-d...
could this be used for HDMI input, in theory, right?
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