Hacking an RC transmitter - and the state of hobbyist affairs - Page 1
Forum section: electronics / projects

author: brainwash
author_rank: Frequent Contributor
timestamp: November 06, 2012, 08:32:36 pm
content: Hello all,Here's thelong story:Less than one year ago I got into the RC hobby and found myself creeping towards higher priced products. Well, the RC remote I finally settled with is a Spektrum DX6i. Decent build, decent modern features, renowned manufacturer, cheaply available reliable 3rd party receivers.As one of my friends also had a DX8i, costing about three times more, I later had a chance to compare the two and immediately found two must-needed features.In order to save cost (?) and not cannibalize its higher-end RC transmitter market (most probably) Spektrum has decided not to include a cheap backlight on the LCD. Also, while it has a timer for counting how much you are in the air (or in the ground) you have to manually activate and deactivate it, while on the DX8 it can be assigned to the throttle cursor. That's just mean.So the end result is that the pretty cheap LCD has a low contrast without a backlight and that you have to remember to pull on a switch while you are accelerating and pull it again when you stop running your engine. And to remember which state it was previously in.I wrote an email to Spektrum asking for some explanations since I also found other bugs in their software, but they were kindly enough to send me away with something like 'it just works' (copyright Apple) and 'buy the higher end model'.Sleeves uptime.I opened up the remote, probed a few signals with a DMM and figured out what to control and where to get power from. I had a few 10F222 laying around the 'shop' so I quickly hacked some C code and an hour after dismantling the remote I had my model upgraded with the missing features. One of those few times when all things actually click together. One week later I ordered the backlight and everything has been running fine ever since.Step twowas to actually brag about this and present the solution to people, so I wrote one of my first posts on a big RC forum explaining that I can offer the solution to anyone, for FREE. Mind you, there another two people doing business with these kind of stuff - somewhere around 30E for this kind of capability - so I did not want to 'eat' their market. I just said that if anyone wants this I can give the firmware and details to them. I got about two replies, from people selling the their stuff.Oh, and the usual youtube-like comment: 'plz src'.Download count: 5.Fair enough, it was in total about two-three hours of coding for me, mostly spent how stuff works, so I published the sources in my already existing Google Code project. I also submitted the project to Hack-a-Day and it got an article page.Download count: 10.You have to draw your own conclusions from this, but just know that people bitch and moan about these missing features but don't want to invest 33c in a chip, some wires and 20 minutes of fun, but actually pay the 200E to upgrade. Of course they won't use the high-end features, it's just like buying a Rigol 2000 to replace the older 1000 just because it has better specs and bigger screen.Current download count: 17.I suspect most of the people are downloading the source and binaries to a 'TL;DR' folder somewhere that will never see a mouse click. I do this all the time.Anyway, if you made it this far and care to spare a few more minutes, please also review my code and project presentation, it's my first open-source embedded project.http://code.google.com/p/dx6i-enhancements/

author: ceecrb1
author_rank: Contributor
timestamp: November 06, 2012, 08:45:30 pm
content: Cool! and welcome to the world of RC! (better later than never)..I fly 3d gassers at weekends, and I have to admit am a futaba manThe only reasons I can think of for the lack of those features and that responce from spectrum is that really.. the lower end TX's are more sold as "beginners" models, so they are deliberately kept simple to use and program.So many "pilots" in the rc world TBH are, well, not young.. so computer tx's dont seem to come naturally to them.. I`m with out a doubt the youngest in my club (at 32!!) and I have to help out a lot programming other peoples radios.I'm also one of the club instructors and see so many newbies appear and need a hand to get going.. and in that stage, yes I really agree with the manufacturers keeping the lower priced TX's simple... if only because I dont get so many "what does that do?" questions LOLAny time you feel like getting your nose into a futaba 8fg and reworking a few things.. dont be shyOut of interest, which RC forum did you post in?

author: brainwash
author_rank: Frequent Contributor
timestamp: November 06, 2012, 10:00:14 pm
content: Hi and thanks for the welcome.I think it was the largest one, rc-groups, but I might have posted in the second one (as size) as well, which name I kinda forgot. Well, it was a pretty useless experience there, trying to: determine why my 2 identical cheap micro helis don't want to fly straight; publish this hack; discuss the power train for a DIY micro 3D plane project. Not truly fair for them, for the last one I actually put some math into an Excel and I suppose that's where the discussion died.I think the engineering approach, back-of-the-envelope maths and 'let's open it up first' do not really go well with some groups of people. The other group is probably gathered here; I'm always amazed of the number of hacks and the determination some users around here have.If I get my hands on a Futaba I will certainly open it up first, but I don't think that will happen too soonIf you have anything in mind and since you are here you can tell me what you are trying to achieve and I will do my best to assist you, even going as far as buying one of those gadgets.I'm still a newbie in the RC field, it's just more of a relaxing hobby to me than a passion. It's just that it's a nice area where building and electronic and repairing skills converge with fun, both inside and outside the house. With the current weather it's more likely inside.Oh, later edit: I noticed you are also an instructor: nice, I wanted to join a local flying club as well. For me it's pretty hard being in a country where I understand 60-70% of the spoken words and able to talk 20%. Sure, I can default to English most of the time, but it kind of defeats the purpose and it's a bit frowned upon, but can't blame 'em.And to actually elaborate a bit about your theory with - 'keeping it simple' - I don't think it's the case. The DX6i remote provides some obscure features like throttle curve, pitch curve, dedicated separate v-tail and delta mixing, all kinds of mixings (except throttle with throttle which again is a glaring omission), gyro gain, 120 or 90 deg CCPM, ...What I'm trying to say is that to include those very advanced features which <10% users actually touch but to omit something like knowing how much flight time you still have smells like a marketing dung.