Picture of my ground station and sample video of a weak link
In this post I’ll explain my ground station that receives and displays video data using wifibroadcast
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My ground station
Let’s start with a picture:
Here you see my ground station. To the left you see my FPV glasses which contain a 7″ HDMI display and a fresnel lens. The enclosure is made out of foam and at the back a strap from ski-goggles is attached. Right next to the “helmet” you see a 3-cell battery that powers the system. On the right you find the Raspberry Pi A+ that has been integrated into a USB hub enclosure (there was enough room to keep the hub :). The Raspberry is powered by a cheap 5V DC/DC converter.
Sample video of a weak link
Following is a video where I have intentionally removed the antenna from the receiving wifi dongle. This shows some of the artifacts you could experience under bad signal conditions. I know, it looks really bad but remember: A lot of bad images and some good images is better than no images at all. And to get bad images like that with an antenna attached you really need a high distance or a solid block of the line of sight.
Hi. How are you powering the raspberry Pi on your quad? I just blew mine using a 4S Lipo even though I used a 5V UBEC :(. The UBEC i was using is here:
http://www.getfpv.com/lumenier-ubec-5v-5-5v-6v-5a-2-6s-input.html
I’m sorry to hear that. Luckily the Raspberries don’t cost so much. You can find a part list of my quad here: https://befinitiv.wordpress.com/2015/04/07/details-about-my-flight-setup-and-first-tests-of-wifibroadcast-in-the-air/ . The quad uses a OKLT1W12NC . However, this is limited to 14V at the input (which is fine for me since I use 3S). For my raspberry on the ground I use this converter here: http://www.pollin.de/shop/dt/NTU0ODQ2OTk-/Stromversorgung/Ladegeraete/USB_Ladegeraete/KFZ_USB_Lader_HAMA_PICCO_2_1_A_schwarz.html . Datasheets says it works up to 16V so that might just work. Maybe it’s worth trying since it costs only 3€.
I tested this with a multi-meter and it seems that the BEC is putting out the same as it gets in regardless of how the jumpers are set. No idea why!!
I have a question about your goggles, I’m planning to build one too and found the display from pollin. But I calculated that in case of a 2x lense the focal distance would result in a very long
lever hurting my neck. And in case of a lense with shorter focal distance it would result in a very large virtual screen in front of my nose. What lenses are you using and what is your viewing experience?
Hi)
How can i run test video/signal or other source acros ./tx?
sudo gst-launch-1.0 videotestsrc pattern=smpte | sudo ./tx -b 8 -r 4 -f 1024 wlan0
it does’t work(
If I understand your command correctly then this would send raw video data. The data rate of that is most likely to high for wifibroadcast. You would need to add a H264 compression element into the gstreamer pipeline.
Another way would be to send previously recorded video data as a test pattern. There you could control the data rate using the “pv” tool.
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