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ELRS and SBUS is a thing now
#1
Information 

It's in a development branch of the firmware at the moment, but it should be pulled in to the main branch soon.

I have no need for it yet; all my stuff is PWM only, but it's a pretty cool addition.

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#2

The main use I have made of sbus with my frsky gear has been a lipo voltage monitor, that allows you to monitor cell voltages and give a warning when the lowest cell in the pack falls below 3.6v.

Using ELRS on my planes I have not been able to reproduce this. It seems you would at least need a separate flight controller attached to the elrs rx. ELRS Drones routinely allow voltage monitoring but for planes it is not so simple.
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#3

The matek r24 receiver has a voltage input (up to 34V) on the 7th set of pins. It's reported back in telemetry as RxBt.

I use it to report the total pack voltage via the balance plug in my batteries. You could do it for a single cell in the pack as well
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#4

Just a reminder that S-port is very different to Sbus.

I read that ELRS will never have S-port as it belongs to FRSky.

srl
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#5

Are SBUS servos very common? I've never seen one in the wild.
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#6

I use a adapter in my trainer wing to run two servos, only time I've used it. I think its for flight controllers.
S-port is great in that you can conect it to a blheli-32 and know a bit more.
Here is a basic FRsky RX with both- https://www.aliexpress.com/item/10050050...2709%21btf&_t=pvid:831238e5-9455-49da-a8f2-d02b05406f6d&afTraceInfo=1005005011245102__pc__pcBridgePPC__xxxxxx__1680934582&spm=a2g0o.ppclist.product.mainProduct

srl
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#7

(09-04-2023, 01:02 PM)caffeine Wrote:  The matek r24 receiver has a voltage input (up to 34V) on the 7th set of pins. It's reported back in telemetry as RxBt.

I use it to report the total pack voltage via the balance plug in my batteries. You could do it for a single cell in the pack as well

I use a Matek ELRS-R24-P6 ExpressLRS PWM Receiver with 7 sets of pins on my 1m Flash 3D plane, but I have never tried to measure total pack voltage. Now I will try it! I think it should work well to indicate when to land, even if its not quite as good as the Frsky system with an external voltage sensor that monitors all lipo cells in the pack and reports on lowest cell.
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#8

Yes, that's the same receiver I use.

It's a common ground with the battery so you only need a single wire to the sense pin. I use a jst-xh terminal to connect to the battery balance connector.

I bought a pack of 10 jst connector pairs (male and female) with wires already soldered on, for $0.02 shipped to my house from AliExpress 😆 (plus $0.28 GST, so $0.30 all up)
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#9

(09-04-2023, 08:34 PM)srl Wrote:  I use a adapter in my trainer wing to run two servos, only time I've used it. I think its for flight controllers.
S-port is great in that you can conect it to a blheli-32 and know a bit more.
Here is a basic FRsky RX with both-  https://www.aliexpress.com/item/10050050...2709%21btf&_t=pvid:831238e5-9455-49da-a8f2-d02b05406f6d&afTraceInfo=1005005011245102__pc__pcBridgePPC__xxxxxx__1680934582&spm=a2g0o.ppclist.product.mainProduct

srl
I have a Frsky R9 Slim +OTA rx that uses s.port to connect to a PWM adapter. This uses an ACCESS protocol, but there is also a ACCST version, FrSky R9 Slim that looks very similar, although may not be still readily available.
The Frsky Access R9 requires a Frsky tx such as the Tandem X20.

For my R9 Slim +OTA rx I purchased an adapter for PWM servo plugs
"Receiver Adapter For Crossfire Nano RX/ FrSky R9 Slim/ Slim+ Receiver PWM Signal Output For Flap switch, LED light Switch Plane
2 PCS AU $15.01 from Top Gun at Ali Express  Feb 26"
I have not got around to using this rx yet, I like how small and light it is but I have reservations about the ultra-fine wiring set on the adapter (what if one micro-wire snaps?), and also I have a niggling doubt on the quality of the adapter plug that fits in the rx (see photo of R9 and adapter).


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#10

(10-04-2023, 03:49 PM)caffeine Wrote:  Yes, that's the same receiver I use.

It's a common ground with the battery so you only need a single wire to the sense pin. I use a jst-xh terminal to connect to the battery balance connector.

I bought a pack of 10 jst connector pairs (male and female) with wires already soldered on, for $0.02 shipped to my house from AliExpress 😆 (plus $0.28 GST, so $0.30 all up)

I'm thinking out loud about the above. So for pin set 7 on rx, the JR plug with 3 wires keeps its white (signal wire), and red (+) wire, and I cut off the black (-) wire.

For a 3S lipo, there are 4 balance plug wires, including a black ground wire which I will not connect, and a red wire, separated from the black by 2 wires at the balance plug.
Turnigy: beside the red there is blue, then yellow, then black
Zippy:  beside the red there is yellow, then white, then black
Dualsky: beside the red there is blue, then blue, then black

I expect I will connect the red JR wire to the red balance wire, and then the white signal JR wire has 2 options (connect to the balance lead next to the red, OR the balance lead next to the black.  
 
What do you suggest?
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#11

On the matek receivers, what would normally be in the signal position (white) on pin set 7 is the sense pin. (I soldered a red pin into that position on mine)

For total pack voltage sensing, that should be connected to the red wire on the balance plug.

The red and black of pin set 7 on the matek receiver do not need to be connected to anything.

On your balance connector, the black is ground, the red is total pack voltage. The other 2 tap into the connection between each cell in the pack.

You could monitor just the voltage of the lowest cell by using the first wire next to the black, or the total pack voltage by using the red.
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#12

Here's a picture showing what I mean

[Image: Matek-Battery-Sense.png]
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#13

And don't connect the red balance wire to the centre pin, it will put the full pack voltage into everthing on the 5V line, potentially breaking things like servos and speed controllers
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#14

(10-04-2023, 09:27 PM)caffeine Wrote:  And don't connect the red balance wire to the centre pin, it will put the full pack voltage into everthing on the 5V line, potentially breaking things like servos and speed controllers

thanks, that is clear, I will try it.
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#15

(10-04-2023, 10:12 PM)greggold Wrote:  
(10-04-2023, 09:27 PM)caffeine Wrote:  And don't connect the red balance wire to the centre pin, it will put the full pack voltage into everthing on the 5V line, potentially breaking things like servos and speed controllers

thanks, that is clear, I will try it.

the total pack voltage works perfectly, thanks, the diagram was really helpful. I now have it installed in one plane and soon I will put it in a second.
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#16

Great news! Good to hear that it worked as expected.
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#17

(11-04-2023, 11:18 AM)caffeine Wrote:  Great news! Good to hear that it worked as expected.

I also have 2 MATEK ExpressLRS ELRS-R24-V Receiver × 2 (ordered from Drone Parts Garage on 25 Oct 2022 $76 for 2 rxs ).
These offer voltage sensor: "36V Max. battery voltage sense (1K:10K voltage divider built-in), RxBt,Curr,Capa,Bat%,GPS telemetry and VSpd(Vario)". They have 6 sets of PWM, numbered 1,2,3,4,6,7. (I dont know where 5 fits in). But I expect if I connect the balance lead to pin 7 (as described above) this may work to monitor pack voltage. I will check this out.
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#18

I was looking at those ones. As channel 5 is the switch channel, they provide it as a pad on the board (see left most PCB in this image), but you don't need to use it.

[Image: MatekExpressLRS-ELRS2.4ghzVarioReceiverRLRS-R24-V.jpg]

You should connect the battery balance red lead to the 'VBat' pin shown in the left and middle images. Don't stick it on pin 7!

Here's a good illustration of where to wire everything:

[Image: ELRS-R24-V_4.jpg]

The only drawback seems to be having to separately update the firmware on 2 different boards.
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#19

that is really helpful, thanks. I will put a R24-V in a plane soon and check it out. I am going to get several more Matek ELRS-R24-P6 rxs, do you have a favorite matek dealer?
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#20

I buy mine from PhaserFPV (https://www.phaserfpv.com.au/collections...lrs-r24-p6)

They have always been overnight shipping for me.

I'm thinking of getting a small breakout PCB made up to assist in mounting these receivers. I'm finding my usual option of adhesive backed velcro isn't the best when they're so tiny.

[Image: Matek-Breakout-1.png]

[Image: Matek-Breakout-2.png]
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