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Online Deerslayer

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Some new radio development information
« on: December 13, 2019, 01:49:39 PM »
For a number of years, almost since they first appeared, I have used Lemon 2.4GHz receivers, both DSM2 and DSMx compatible ones, some with their original Stabilizer and some with the additional self-righting capability (the Lemon Stabilizer+), in 6-channel, 7-channel and 10-channel variations. They are all excellent, have been proven in tests by skilled technicians to have equal or greater range and reliability of the common manufacturers' units. I have never had an issue attributable to a Lemon receiver itself. As I was preparing to order a couple more Stabilizer+ units, I checked into the status of Lemon's developments, learned about their upcoming units that have been a couple of years in development and the situation on the common chips that manufacturers are currently using and which are now ending of production.

OK, there is a bit of a point to all of this! Lemon utilizes real Users to assist in beta testing, feedback of experiences and suggestions, etc. The two main ones are a fellow in Australia and one up here, near Ottawa. In fact, the Lemon manuals are products of their work, combined with contributions from other users.

The Australian chap has written the following very nice summary of Lemon's and others' current undertakings in this area. Note: He mentions the Multi Protocol Module - that is what is in the Jumper which a couple of us are using to run OpenTx. Here is John's write-up:



For folks who don't have a technical background what this means is this:

Traditional 2.4 radio transmitters and receivers use a separate microprocessor which does all the decision making, decoding, outputting/inputting servo pulse and stick positions etc etc and this was received from or sent to a separate dedicated 2.4 radio frequency (RF) two way transmitter/receiver module. These RF modules have been supplied by only four manufacturers for the majority of radio systems on the market (Futaba is an exception as they have their own custom RF chips because of their background in Industrial radio control - there may be some others like Jeti, I know little about their system). Because the RF modules were mass produced in large numbers for the WiFi market, our radio sets could be relatively inexpensive .

The separation of the control microprocessor and the RF chipset is what enabled things like the popular Multi Protocol Module which plugs into the back of a Taranis or similar transmitter. It started as a DIY project which put all 4 of the common RF chips on one board and selected the appropriate one. Because the microprocessor and the RF chipset was separate, clever hackers were able to monitor the data traffic between them and reverse engineer the various proprietary protocols such as Spektrum DSMX and FrSky ACCST and dozens of others. The Lemon receiver designs were never copies of Spektrum designs but they did use the same widely available RF chipset - the Cypress CYRF6936.

The common RF chips are old and in the process of being discontinued. Specifically the Cypress CYRF6936 chipset on which Spektrum and Lemon relied is EOL.

The new approach is to use a chip that includes both the RF stage AND a powerful microprocessor such as an ARM Cortex. The radio vendors like this as it is virtually impossible to reverse engineer the protocol as there is no external data path between the two. For example, FrSky have changed protocols from ACCST to ACCESS as a result.

Spektrum have chosen the Texas Instruments CC2650 ultra low power wireless 2.4GHz chipset for their new receivers (and presumably transmitters - I haven't investigated this). Lemon have chosen a different chipset so from now on Lemon designs are not only completely original but they don't even use the same hardware as Spektrum devices.

Designing a receiver that runs entirely in one of these chips is no easy task. It is called a Software Design Receiver or SDR because both the receiver logic and RF implementation are basically defined in software not hardware. Lemon is pretty good at this, and as FMak suggests it is possible to emulate almost any RC protocol with a clever enough design.

For the moment however they are concentrating on getting DSMP right. This is the Lemon protocol that is also backward compatible with DSM2 and DSMX.
For some time Lemon receivers have been manufactured with their new architecture and it seems to be working fine.

Although it is technically possible to design firmware that would do Futaba, FrSky, FlySky etc as FMak says, it is not simple and does not necessarily mean it will actually happen - so don't get your hopes up just yet.

John
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Offline ganguy

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Re: Some new radio development information
« Reply #1 on: December 13, 2019, 03:15:28 PM »
I need to summarize out loud so that you can tell me if I am correct:

 - Our current DSM2/DSMX receivers will continue to work with our Spektrum transmitters
 - A new one with MPM protocol is in the works
 - We can continue to buy DSM2/DSMX


Am I?
« Last Edit: December 13, 2019, 03:17:33 PM by ganguy »
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Online Deerslayer

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Re: Some new radio development information
« Reply #2 on: December 13, 2019, 05:38:03 PM »
Nothing will change, from our point of view, at least for a long time to come. There are receivers now being sold that are based on the newer chip sets and firmware.

I buy Lemon gear, it is fully compatible with all Spektrum transmitters now on the market. I am about to order a couple more Lemon DSMX-compatible receivers and expect I would be able to do so for a long time to come. My new Jumper transmitter, with its Multi Protocol Module, can work with just about everything out there - a dozen or more manufacturers, with the latest to be added being Graupner HOTTS.

Will folks from the OpenTx group be able to reverse engineer future protocols, based on the upcoming hardware? My bet is, Yes, albeit with some difficulty. The technical community behind OpenTx is large and extremely strong.
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Offline ganguy

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Re: Some new radio development information
« Reply #3 on: December 13, 2019, 06:17:27 PM »
As I thought. It sounds like a non-starter for we casual flyers, at least for the foreseeable future, which in my case is becoming shorter every week!
I've got about a dozen Lemons in my planes, and I like them, although I'm not using the Lemon Plus to its best advantage. You ought to think about doing a YouTube video on how to use it, I think it would be widely appreciated. In fact I can see a whole series of Deerslayer YouTube videos on various RC matters. There are lots of subjects which have never appeared there.
Churchill said: "Success is a series of failures during which one does not lose enthusiasm!"

Offline Bill H

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Re: Some new radio development information
« Reply #4 on: December 13, 2019, 06:23:58 PM »
I have suspected that someone at the club with a jumper radio may have been hacking my airplanes in mid flight.
All of a sudden the unexplainable incidents to many club members planes may come to light.

Offline Terry

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Re: Some new radio development information
« Reply #5 on: December 13, 2019, 07:57:39 PM »
I've been Hacking ever sense I joined the club, Tree's mostly , You know,  to get my plane out.

Offline ganguy

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Re: Some new radio development information
« Reply #6 on: December 13, 2019, 09:18:48 PM »
Terry - I remember that you once climbed a tree for me to retrieve my very first plane! It was stuck in a tree over on the military property. Remember that?
Reg
Churchill said: "Success is a series of failures during which one does not lose enthusiasm!"

Online Deerslayer

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Re: Some new radio development information
« Reply #7 on: December 14, 2019, 05:28:10 AM »
Hence, his official call sign, "Tree D". He was once upon a time what ya call a bush pile-it, or so I have heard.  But, he really is a pretty good fellow - most of the time - and an excellent flyer.

Hey, Tree D, come on out and join the Numb Thumb Flyers. We meet frequently at a Toyground near you and would enjoy your company.

   ----------------------

Well, this little topic has now been nicely derailed - it was on a pretty short track that not very straight to begin with  :)

In any case, here is a little war story, typical of my use and experience with stabilizers:

 I recently built a really simple little seaplane/snowplane called the Shrimp. It flies very well, but, I could see room for improvement. So, I built a slightly larger, similar plane. I think it looks a bit nicer, so I called it the Swan. It has a Lemon Rx/stab.

As usual, I set thing up so that the stab had somewhat medium Gain on each of the primary controls, and Master Gain on the Tx knob. For the test flight, I took off from snow, with the stab turned Off. Had I needed to hand launch it, I would likely have turned the stab On.

It took off and flew OK, but was a bit twitchy. No  big surprise, considering my design changes, plus a rather aft CofG, which I tend to like. So, I flipped the stab On. Wow! Sweet plane!

It wanted to oscillate in roll at higher speeds, so I just cranked the Master Gain down somewhat. (I set my OpenTx system to call out this Setting any time the knob is moved more than 5 units up or down - very useful information for later locking in my settings.) As I became more used to the plane, I would alternate between using and bypassing the stabilizer. That gives me valuable insight into the overall characteristics of an aircraft and ideas about what changes, if any, I might want to make to it or when I hack out the next generation (maybe even today?). First flight completed, many more that same day, no need to touch the plane itself. Before the next flying day, I will hack into the foam fuse, and tweak the Elevator Gain setting on the Rx. I may decide to leave the Master Gain on the knob, at least until I have flown in the total range of wind conditions. I LOVE  windy days, good planes and effective stabilizers - it brings out the adrenalyn, and the sky is not crowded.

So, once again, a stabilizer did exactly what I expected and why I use them. I have created some things that were very challenging, perhaps even somewhat nasty to handle, especially if hand launching was required. Yet, these became really solid and big fun as long as I remembered to engage the stabilizer along with my tired old brain, before flinging them into the air.

In the aftermath of fracturing and dislocating  my shoulder, the only reason that I could readily launch my flying wing collection is the Auto Launch Sequencing that I had come up with some time ago. Its fundamental component is a stabilizer with self-levelling capability, such as the Lemon Stab+, BIGAOLE or Guardian.

See you at the Toyground!

« Last Edit: December 14, 2019, 05:34:10 AM by Deerslayer »
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Offline ganguy

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Re: Some new radio development information
« Reply #8 on: December 14, 2019, 08:43:24 AM »
Your experience with stabs is a lot more effective than mine, maybe we should have a stabilizer workshop at the next meeting of the NTF's. Even Maggie flies better with it off than on!
Ganguy
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Online Deerslayer

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Re: Some new radio development information
« Reply #9 on: December 14, 2019, 03:45:47 PM »
Even Maggie flies better with it off than on!
Ganguy

Yes, because she is the "stable genius" of foamys. Treat her well, sit down and just watch her fly!
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Offline ganguy

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Re: Some new radio development information
« Reply #10 on: December 14, 2019, 04:17:07 PM »
I've got more hours on Maggie (actually Maggie 2 - you gave me the parts for Maggie 1) than any other plane except the SU 27
Churchill said: "Success is a series of failures during which one does not lose enthusiasm!"

Offline Terry

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Re: Some new radio development information
« Reply #11 on: December 15, 2019, 03:39:59 PM »
Reg I remember it well. It was the day we both got our wing's. I still have picture's of It with branche's stickin out of it  then Gord hot glued it back together so you could fly it and get your wings. With Gary's approval of course.

Offline ganguy

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Re: Some new radio development information
« Reply #12 on: December 15, 2019, 04:12:30 PM »
What a memory!
Churchill said: "Success is a series of failures during which one does not lose enthusiasm!"