New FPV option - FPV HAT for Raspberry Pi

Hi all,

I would like to introduce you to an Open Source, low-cost digital FPV video transmission option!

https://www.tindie.com/products/FernTech/fpv-hat-for-raspberry-pi-/

Our FPV HAT for Raspberry Pi 2/3 has these key features:

  • Max. data rate approx. 500 kbit.

  • 433 / 868 / 915 Mhz versions available.

  • Supports AES-256 encryption.

  • Useful for e.g. long-range and/or NLOS SD "analog quality" video links (e.g. 512x288@49fps or 640x360@30fps)

  • OR high-res-but-low-frame rate DIY-surveillance/Robotics/RC/etc. applications

  • OR anything else on a Raspberry Pi that could use a 500kbit wireless UHF one-way data-link!

  • Set of two boards cost 70 USD (Rasberry Pi, antennas, camera etc. not included). In stock. Free Shipping.

The FPV HAT has been developed to enable wireless transmission of hardware encoded h.264 video streams from one Raspberry Pi to another.

The available bandwith is limited to 500 kbit which in turn limits the possible resolution while still maintaining reasonable fps and latency. Video quality is comparable to analog PAL/NTSC video.

But if e.g. your ground rover needs UHF ISM-band video in the 433 Mhz band in order to send the signal through walls or vegetation. Or you want to keep your video stream truly private using hard 256 bit AES encryption, then this might be the board you need!

Also, compared to analog video, bandwith use is very limited at either approx. 300 Khz (2GFSK/300kbit) or approx. 600 Khz (4GFSK/500kbit). User defined frequency offsets in software enables a number of concurrent streams within the respective ISM bands locally.

Please note that this system requires some knowledge of Linux and Raspberry Pi to use. Users may also need to adjust transmit power to comply with local regulations.

FernRF

Views: 3356

Comment by JeanLeFlambeur on March 27, 2017 at 12:28am
This looks great! Which module did you use? Is it the RF4463F30 one?
Comment by Pascal P. on March 27, 2017 at 12:42am

Sounds nice.

Any distances achieved in trials and videos showing setup and footage quality ?

Comment by FernRF on March 27, 2017 at 6:45am

@JeanLeFlembeur: Thanks! yes, its the RF4463F30 module.

@Pascal P.: Thanks! We're working on videos demonstrating setup and longer-range trials. So far the ground-rover use case has been tested but not video'ed. Using the 868mhz variant and raspivid bitrate set to 440 kbit the signal went through a large apartment block. Something we've been unable to do with either Wifibroadcast or analog 1.2 ghz video.

FernRF

Comment by FernRF on March 27, 2017 at 6:47am

PS: Forgot mention that we used an inverted vee antenna on transmitter and a pcb-moxon antenna on receiver. Both pretty compact and cost-effective.

FernRF

Comment by JeanLeFlambeur on March 27, 2017 at 10:54am

@FernRF - do you happen to know what version they are?

I tried to get 2 of them to work for 3 months without success. They got unstable at higher power levels (>50mW) and the power rail got a lot of noise. My guess is that the power amplifier draws too much power and causes the Si4463 to restart.

Anyway - did you have any issues with your modules?

Could you share where you bought them?

Thanks a lot!

Comment by FernRF on March 27, 2017 at 11:37am

@JeanLeFlambeur: Sorry to hear that. We haven't seen that issue. Current products are made with version 2.1. Only issue have been some early problems with the 915 mhz variant. But these were caught by our QC. We buy the modules directly from the producer NiceRF. They also sell on Tindie, like us BTW.

FernRF

Comment by FernRF on March 27, 2017 at 12:00pm

@JeanLeFlambeur: Come to think of it, your problems might related to some challenges we had earlier on. It is possible to run the si4463 chip outside the specified module PA freq range. In that case its only the si4463 chip inside which transmits. If your receiver is close by, your can actually receive that signal, despite it being quite weak. Then, when you try to run the module within the specified freq range of the PA, the PA turns on and pulls a lot more power suddenly. That can reset the module if your power supply is not up to it. Anyway, you could look into our code and check out the initialization bytes sent to the modules.

FernRF

Comment by JeanLeFlambeur on March 27, 2017 at 12:36pm

@FernRF: thanks a lot for the hint PA. I will definitely check out your code. It might be what you mention, maybe I got the wrong frequency modules or I had the wrong configuration - even though I doubt it, I was measuring with a SDR and spot on 433 MHz with 500Khz modulation.

Anyway, I'll give it another chance with new modules, just in case.

I have a few more questions - why aren't you using 1Mbps data rate? The module can handle it according to the datasheet.

I guess the 2 caps on the PCB are for decoupling the rf module. I've seen a value of 47uF/ceramic in the datasheet. Did you need more than this?

I didn't check the code in detail yet - are you using the combined 128 byte FIFO? This could give you a better data rate as the packets will be bigger.

Cheers

Comment by FernRF on March 27, 2017 at 12:54pm

@FernRF: Its true that the data sheet says 1 mbit. And the hardware might even support it. But SiLabs configuration software only allows initialization up to 500 kbit. I suspect that the receive sensivity gets so low that it isn't worth it. But if you're up for it, you might design your own initialization bytes and see how it goes ;) These radios are rather flexible and there are other outside-spec possibilities with them.

Re the extra caps: That was just to be sure that there are enough power on tap.

FIFO: You mean the on-chip one? yes.

FernRF

Comment by JeanLeFlambeur on March 27, 2017 at 1:46pm

@FernRF Actually the datasheet says the max is 500k symbols per second. With 4FSK a symbol is 2 bits so a max rate of 1Mbps. This is well within the specs.

The RX sensitivity @1Mbps is -88dBm which is very usable.

Regarding the fifo, I was curious if you used the split 64RX+64TX fifo mode or the combined 128 bytes one - which would make sense in your case as you have unidirectional comms. 

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