ExpressLRS 3.0 Packet Modes Explained

[@jeffparisse4202]

I appreciate your “cut to the chase presentation” style and definitive suggestions for the viewer. I hear every word you say because each is well chosen and adds value to the subject. You earned my sub after the first video. Thanks again!

[@barthchris1]

I was just about to say something similar. I prefer reading vs vids because its faster. I would prefer vids if they were all info, no fluff. Subbed as well.

[@DaRoach5882]

Thank you so much for all your hard work and dedication to ELRS! it has revolutionized the hobby!

[@jimn6sxb644]

You are Da Boss CapnBry. Excellent information and concise presentation. Thanks for your incredible contributions to the RC community.

[@tillyFPV]

this channel needs more subs and viewers!!

[@deadbyteDrones]

Thanks for your work Cap'n. And thanks for this video!

[@Kleinage]

Great video! Excellent presentation. Comprehensive, helps me a lot as a quad pilot starting to add fixed wing.

[@youtubxkip]

OMG, thank you, I finally found ELRS developer who have a KZbin and can explain in more details than on a elrs website! I'm still looking for even more details towards how data and packets are aligned in time on air and how this is all packed together, not sure I get it right: 1) Normal Range vs CRSF Extended - yes, I'm a quad pilot and my world is clamped between -100% +100% :D but just want to make sure I get it right, so far my understanding is "the range" is all about PWM ~1000~2000 compatibility, about the way sticks are reported to TX and RX communicated value to FC or servo, so CRSF is here to help with that, right? My understanding is that it have nothing to do with air transmission over digital protocols. I assume ELRS encodes, modulates the bits in a packet (without knowing the range), so no matter if extended range is in place or not, it gives same precision, same amount of bits and never have any effect in air transmission, is it correct? Even though I'm seasoned developer it is hard to grasp from your 60 seconds explanation of range compression in ELRS3. Still can't get how LoRa have something to do with compressed/full 10 bits? 2) Am I right that in Hybrid mode the packet size is slightly smaller and might give slightly less OTA latency? Plus in Hybrid mode it needs 7 packets to RR over all channels, while with Wide the packet is slightly bigger and it needs 8 packets to RR over everything? Do I have to bother myself with Hybrid mode nowadays for racing/freestyle? I kind of stick to it, but most people saying it have no advantage over Wide, only disadvantages in terms of precision, I really want some insights into it before I connect an oscilloscope to measure :D 3) Why 3 bits gives 7 positions instead of 8? Never was able to find it. ELRS documentation says that I can use 6 pos switch with e.g. CH6 in hybrid mode, but since for 3pos the 1500ms also mapped, I can perfectly use not 6 but 7 positions (I use 6 pos switch + override for turtle mode in 0% 1500ms, works great). Still not sure why not 8 positions if this is 3 bits? Is it artificial limitation in a mapping to get a middle point for most of other use cases? Or this "half bit" is reused later to improve something else (e.g. CH12 precision?) I would be so grateful if you can make a little longer videos for oscilloscope-friendly nerds, please 🤣 You know so much tiny important details that I'm eagerly looking for. Thank you for your contribution! I wish I can contribute to the project, but can't find more technical details about modulation, packet structure, timing etc...

[@CapnBry]

That's a whole lotta questions to answer in a youtube comment, but I appreciate your enthusiasm. You might want to take it over to the rcgroups thread for future replies. 1) In the air we have space for 10 bits of data for a channel, the handset gives us 11 bits and we send the RX 11 bits. In 2.x we would just divide by 2 to get 11 bit to 10 bit, but that throws out the source precision for allowing a wider range. In 3.x the fullres modes still do that but the other modes just slice off the high and low 11 bit values to and map 988-2012 into those 10 bits, keeping precision but lowering channel range. 2) Hybrid and Wide use the same packet sizes, it is just how the 7 bits dedicated to switches is used. Hybrid sends a 4 bit index and 3 bits to represent one switch (with an exception for the last channel), Wide uses all 7 bits for one switch and implies which switch it is. Wide therefore needs to have an 8-packet period so the switch index can be determined from the (8-bit) packet counter directly. Hybrid is only still around because so many people yelled at me when I tried to remove it, claiming "Wide switch mode will cause so many failsafes". Hybrid is safer than Wide, but only as a backup for when the link is already f*ed. 3) Your math is correct, we only use 7 of the 8 possible values. The requirement is that we properly represent 6 position switches accurately for those 6-pos buttons on handsets to map directly without the user having to set up a weird mix. If we just made each bit represent 125us (1000us range / 8), then you'd only get like 5 of the 6 positions generating a unique value. I couldn't think of anything else to use the extra "position" for since it would have to be used only to represent something about this switch.

[@youtubxkip]

@@CapnBry thankyou very much, now it makes so much sense! 🤩

[@psguardian]

I have only just learned of ELRS, props to you & the rest of the dev team! Thank you, and a big thanks for the expanded support for fixed wing & heli/car.

[@IzzyBoop]

This is EXACTLY what I was looking for (especially that cop uniform lol) Thank you!!!

[@nickvledder]

8:14 Great summary, exactly what I was looking for. For my cruising type of flying quadcopters 150Hz seems spot on, which is what I intuitively expected. Thanks for making great content and sharing it.

[@hkim113]

Nice presentation! It helped me a lot to understand ELRS 3.0 in a short time. I'm looking forward to the next video. Thank you.

[@wattage2007]

If you are Mr ELRS, you sir are a hero!

[@ApappieK]

Nice, great, excellent 😃. Well, I have nothing more to wish from ELRS. I didn't ask for FullRes but NOW I can use it. Thanks 🥳

[@douglasyoung3992]

Man I love you smart guys on KZbin thanks I may eventually learn 1 or 2 things. Express LRS is really expanding and getting more feature filled.

[@rabbitambulance]

🔥🔥🔥 More Cap'n, please!

[@pav2k]

Thank you for your amazing work!!!

[@txkflier]

Just what I wanted to know. Thanks..

[@senseisecurityschool9337]

Thanks for the option to use more channels with ore resolution, at the cost of latency. I don't care mind a few milliseconds because I'm a human, so my own response time is hundreds of milliseconds.

[@EndyMuhardin]

Your audio is way better when you are entering the weed :P

[@CapnBry]

Don't kid yourself, all the audio is terrible! 😔

[@EndyMuhardin]

@@CapnBry no seriously it's better. The echo is gone 😁

[@Widflyinghigh]

Hey, CapnBry, nice! Thanks.

[@FelipeDiasCREATOR]

To use D250 OR D500 mode, do I need to change the RX to operate at 250hz? because in Betaflight there is no profile for D mode, unless you can access the RX via wifi, and you can change this frequency field!

[@CapnBry]

The receiver always operates at the rate the TX tells it to. In Betaflight the preset for D250 is 250Hz, and D500 is 500Hz (they are the same as the non-D presets)

[@Fabvelloso758]

Express LRS already fixed the connection lost bug?

[@h2o40fpv]

Great video thank you.😊

[@soy_leche]

Thank you for all information. Something I've been wondering without finding an answer is why does a low rate increase sensitivity? I mean that in the physics sense, what is going on that enables this?

[@CapnBry]

The rate changes the "spreading factor" of the transmission. Instead of a bit taking 10us to transfer, it takes 100us and the receiver has an easier time detecting it. Like the equivalent of discerning the words bip and bop in quick succession vs biiiiiiiiip and booooooop slowed down.

[@soy_leche]

@@CapnBry Thanks for the explanation!

[@StavrosKor]

Good explanation, thank you. The only point I'm hazy on is what's the advantage of LoRa over Fullres? The video makes the latter sound like a strict superset, yet you recommend LoRa for cruising quads. I'm interested in maximum range for my planes, and don't care that much about latency.

[@CapnBry]

They're pretty close. The LoRa modes have higher packet rates at the same range. 333Hz Fullres = same range as 500Hz LoRa, and 100Hz Fullres = 150Hz LoRa. 50Hz LoRa has the longest range of all of them, but there is no Fullres version of that (it would be too slow)

[@BBFPV]

Hi Bryan. Is there a possibility for an RX to output both CRSF and PWM for gimbal like Crossfire nano RX?

[@CapnBry]

You can but it isn't clean. I have plans to make it available as one of the output options in the webui (select instead of 50hz/etc output). If you need it right now, you can go to /hardware.html and put 1 and 3 in the CRSF fields and remove them from the PWM pins section. It's a bit complicated to get into more detail than that in a KZbin comment

[@nerdCopter]

+1👍just like the 1996 movie Multiplicity, even includes the love-story sub-context 😆

[@egtreadway4232]

im trying to learn express lrs and want to replace my crossfire setup on my inav 3.0.1 wing which is running a matek f405 wing flight contoller, so once i get the 915mhz tx and rx how hard is this going to be to get working, does inav even support express lrs i cant seem to find information on this. any help will be great Thanks

[@CapnBry]

Yes, it works with inav. All you need to do is select CRSF as the protocol for the serial based receiver.

[@egtreadway4232]

Thanks I'm going to place order

[@flat-earther]

can ELRS Rx have dynamic telemetry power?

[@CapnBry]

Not in the same way the TX can, because it doesn't get any information about how well its signal is being received. It also doesn't matter too much because all amplified receivers max out at 100mW which means it won't save much power. In 3.4 though receivers have "match" as a power option to match the power level the transmitter is reporting.

[@user-nz2zi7hu2c]

Thanks for the video! Do I correctly understand that INAV won't be able to take advantage of Extended Limits in Full-res modes and will still only recognize values from 988 to 2012? What is the maximum telemetry rate for Taranis QX7 without inverter mod? The baud rate between the radio and r9m module I use is limited to 115kbps, is there a chance of reaching the limit is I increase telemetry rate to say 1:8 in Full-res mode?

[@CapnBry]

Too many questions! 1) iNav supports more than 988 to 2012 2) Telemetry rate has nothing to do with baud rate, only the packet rate. The max packet rate for 115k is 250Hz and any telemetry ratio works with that.

[@user-nz2zi7hu2c]

@@CapnBry Sorry! :) 1) I just tried it myself - by default OpenTX only sends values from 988 to 2012 and INAV only recognizes values from 1000 to 2000, so to get full advantage of extended range in INAV we need to change Outputs ranges in OpenTX and adjust rxranges in INAV. 2) As I remember Crossfire requires inverter mod for telemetry to work at full speed, so I thought that the baud rate was the limiting factor in their case. ELRS uses the same CRSF protocol, has higher refresh rate and allows for telemetry rates up to 1:2 - why it doesn't run into the same limitations as Crossfire does?

[@CapnBry]

@@user-nz2zi7hu2c Yeah of course you need to turn on Ext.Limits in EdgeTX/OpenTX to use extended limits. iNav you really want your first 4 channels to be 1000-2000 and then apply the larger range to the servos. Other channels you are passing through can use the full range. We have the same baud rate limit as Crossfire due to the hardware, but that doesn't do jack for telemetry because that's constrained by the packet rate, which already limits it to below the available baud.

[@WDZaphod]

Cool, thanks for this! Is there any chance to add the possibility to have different modes per receiver? So my Freestyle Quad uses different mode than the Wing, without the need to change TX Setting? The desired mode needs to be saved in the RX then I guess, like with Crossfire. Not sure of this is possible?

[@FrenzyIncarnate]

Oh boy just found your channel. Please upload more! Love ELRS and love you guys! :elrs_heart:

[@auckwads8169]

dddaaammn thats alot of new modes !

[@auckwads8169]

Also if i run 1000dvda so 250hz 4x sends how does the lq display . Will it justbsay 100 untill its below 25 % as its retrying 4 times ?

[@bengordon7635]

been using lowest latency 250hz for freestyle and cinematic still can go as far as battery will take me on 5in 6s quad

[@soursham]

Great video 👍

[@Atlas_FPV]

Should we have extended limits turned on in the radio? I’ve always just turned it on after seeing a JB set up video and never thought about it

[@CapnBry]

You can if you want the Extended Limits for fullres, but you don't need to. It just lets the OpenTX mixer output go to +/-150%, so it only will be used if the value is outside the +/-100% range.

[@bonfpv]

Thanks for the great walk through. When you said race telemetry, do you mean the lowest necessary? e.g. i use 1/128 coz i rarely look at anything while racing

[@CapnBry]

Nope, I mean the telemetry option labeled "Race" (last in the list currently). That is the same as "Std" when disarmed, but "Off" when armed, and also disables Sync packets when armed (replaces NO_SYNC_ON_ARM). That means 100% of the packets you send in race telemetry mode while armed are channel updates-- zero wasted packets.

[@funkynerd_com]

DVDA? Some ELRS developer has a sick sense of humour! lol

[@egtreadway4232]

Thanks for reply, I've already ordered beta Elrs 915mhz rx and TX. I'm flying a longrange fpv inav wing so what's the best setting for this type flying? I'm new to this system I'm coming over from crossfire and not planning on going back. Thanks again

[@CapnBry]

😆 Did you watch the video at all? Not even the summary section that's 20 seconds long? 100Hz FullRes

[@egtreadway4232]

If I didn't watch the video why would I ask question about video, but thanks

[@user-dy6bt8cb3q]

Thanks for your great video 👌🏻 But how can we change these modes in radio ?

[@CapnBry]

www.expresslrs.org/3.0/quick-start/transmitters/lua-howto/

[@user-dy6bt8cb3q]

@@CapnBry thank for your response 💙

[@he214abc]

how about playing the rc car？

[@CapnBry]

I'm not sure surface RC has nay need for more than 4 channels, so just the standard LoRa 500Hz, 250Hz, or 150Hz (from lowest to highest range) would probably be fine.

[@sarahdaviscc]

The police officer 😂

[@NarcolepticLTD]

That's not what DVDA stands for :D

[@funkynerd_com]

Exactly! It's a punk rock band started by Matt Stone and Trey Parker, the creators of South Park. ;) ;) ;)

[@MrBumbles2]

Just got jb radio master tx 16, trying to learn edgetx and elrs, coming from frsky qx7 lol