RSSI mod on FrSky D8R Telemetry receiver

[pk-surfing]

Hi,

Having started using the FrSky 2.4Ghz 8ch telemetry system for my FPV flying I really needed to get an rssi output from the receiver to feed into my EZOSD so I could see the info in the telemetry in my goggles.

Despite mentions that the latest V2 D8R's from FrSky have the rssi output on one of the side pins I found this not to be the case so I bought an interface kit here...

http://uav.org.pl/product.php?id_product=45

now available as surface mounted components

http://uav.org.pl/product.php?id_product=46

and added a short jumper lead inside the receiver and it is working perfectly  :party:

Doing it this way on this receiver means It is simply a matter of plugging in the leads that come with the interface, adjusting the voltage levels with the onboard potentiometer (I have mine at the moment going from 0.7v to 3.2v) and the EZOSD has a lovely bit of rssi info to work with.

Hopefully I will get out tomorrow after work to give it a try in the air.

More info in this thread
http://rc-cam.pl/viewtopic.php?t=3353

and I think MarekM comes onto this forum sometimes (not sure though)

Paul

[rcmonster99]

Hi, I am very interested in this, could you please give more details on where the jumper lead should be ?

[pk-surfing]

No problem, I have another of my receivers to do today so will take some close up shots of where I soldered the link.

If you have the D8R v2 receiver then it has the advantage that there is a spare pin available on the side connector so it is easy to plug the external interface kit into the receiver so avoiding the need to hard wire it permanently.

so, photos later .......

[pk-surfing]

Here are the photos showing the D8R v2 RSSI mod


The receiver before I open it up



The label needs peeling back on both sides only



view of the label peeled back so the receiver can be opened



top cover removed



This shows the red led lit up, we use the GREEN led next to it to connect to for the rssi interface



I'm showing you the other side of the board, you don't actually need to remove it to just do the mod but I wanted to swap the wire antenna for longer ones.



This is the spare pin we are lucky to have on this receiver, photo shows it alongside the label, we eventually use the pin labelled 'x' to pick up the signal for the inteface.



Solder a fine flexible wire to this pad on the green led, this is VERY small so you need to use a suitable soldering iron for fine electronic work, and get the joint soldered in about 1 second... I use an Antex Cs 18W with a 1mm bit.
If you are not comfortable with this type of work then it's likely you will end up ruining the receiver !!!



This is the link showing where it solders onto that spare pin.



Another view of the completed link



the completed job along with the longer FrSky antenna I added to make aerial positioning easier on my Jamara Roo je (Funsky)



This shows both versions of the RSSI interface that I bought from UAV.ORG.PL



I have now connected the interface, powered the receiver, switched on the transmitter and have a multimeter connected to the interface output.....
This shows the voltage reading with the transmitter next to me on the desk.
The white wire from the interface already has a push connector on it and it goes onto the spare pin on the side of the D8R v2 that is marked 'x'.
The other lead from the interface goes to a servo connector on the receiver to pick up +ve and -ve to run the interface, if you dont have a spare connection you will need to use a 'Y' lead so you can connect the interface.



In range test mode I then moved the transmitter into another room and the voltage drops smoothly as required.
This output voltage is what I feed into my EZOSD so that it can show me the rssi % pecentage on the on screen display when flying.



Transmitter even further away and voltage is lower still.
The output voltage can be adjusted on the interface and to calibrate it correctly I will be doing a range test with a mate to help out, when the servo's start to failsafe I wil adjust the voltage so my EZOSD is showing a % percentage figure I know will be when I need to turn round (I have mine set to show 10%)



And finally the voltage reading when the transmitter is turned off.

If anyone needs any more info just let me know.
:)

[rcmonster99]

wow !!! great info. I will order some boards now...

[Coyote]

Very detailed, spot on Paul great thread :)

[rcmonster99]

More questions... I have the FRSKY receivers but the non telemetry ones ( no connectors on the side) can I still do this by hooking up a wire on the green LED ?

this is the one I have

http://www.giantcod.co.uk/24ghz-frsky-receiver-p-405722.html

[pk-surfing]

Yes it will still work fine, this link is to Marek's page on his website and I think the photo he shows is for the receiver you have.


http://uav.org.pl/en/elektronika/46-ue-01-miernik-rssi-by-mieciu-.html

The main difference is that you will have a permanently attached signal wire from the receiver.


:)

[rcmonster99]

great stuff !!! :)

[MarekM]

Hello,

Paul - thanks for great how-to for RSSI Meter!

There are some new stuff in UAV.ORG.PL:

- LC filter for video power supply (based on Murata SMD chip):

weight - 3 gram including cables, dimension - 10x20mm

- various antennas (main - IBCrazy style)




each antenna indywidually tuned and tested on spectrum and antenna analyzers




video TX antennas with build-in low-pass filter (based in MiniCircuits SMD filters):



Marek

[pk-surfing]

Marek,

Great to have you posting on the forum.

Everyone on the UK forum will be interested in new ready made antenna designs especially anything you have that are for 5.8ghz use as it seems more and more UK flyers are moving to 5.8 to avoid interference with fellow flyers if using 2.4ghz vtx.

I have looked on your site at the LC filter, it looks to be a well made piece of kit.

I know LC filters are used to stop unwanted ac interference travelling through the wiring, could you explain where would be the best place to fit your LC filter in a typical FPV setup ? (power feed to receiver ? power feed to camera ? to OSD feed ?)

Also would you expect more than one to be needed in a typical FPV installation ?

Paul

[rcmonster99]

I like the Vee antenna with the low pass filter. do you do one for 1.3gHz ? will the filter stop the harmonics interfering with 2.4Ghz RC receivers ?

[MarekM]

Everyone on the UK forum will be interested in new ready made antenna designs especially anything you have that are for 5.8ghz use as it seems more and more UK flyers are moving to 5.8 to avoid interference with fellow flyers if using 2.4ghz vtx.

(...)

Also would you expect more than one to be needed in a typical FPV installation ?

Paul

Hi Paul,
All kinds of my antennas can be make for 0.9 to 5.8 GHz bands.
For up to 4.4 GHz - I have good lab. For higher - only SWR measurements (which is enough to make not bad antenna),
so.... if anybody interested - PM me

Rearding LC filters: filtering interferences is a long story, as long as RC flying :)
Small SMD style filters can be used in various places: one is on main power "entry" = just after ESC, before RC receiver. Other - is video power supply, More - other electronic modules power supply (OSD, autopilots, etc). You can use one or more of its - but it depends of existing interferences in your instalation.
There are one more kind of filtering - signal lines from receiver/autopilot to each servo. For this - I just now preparing PCB whcich can be connected firectly to RC receiver.

Marek

[volto]

Having trouble getting the rssi buffer to work on my non-telemetry receiver. Shows the same voltage regardless if the radio is on or off. Any help is appreciated.

uav.org.pl frsky rssi not working

[pk-surfing]

Hi Volto,

Is there any chance you could take a really close up clear photo of the receiver board to show the connection onto the led, one using macro mode on the camera would be ideal.
The connection point is so small that could be easy to get the new wire touching an adjacent track.

Its difficult to see on your video but of the two leds, one red and one green, it is the green one you have connected to isn't it ?

PK