SeeDeR: SkyCube's AX.25 data transmission decoder.

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schrambo
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Joined: Sat Mar 02, 2013 1:33 am
Location: Perth, Western Australia

SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by schrambo » Wed Feb 26, 2014 3:25 am

Hello everyone.

A fellow work colleague who contributed to the SkyCube Kickstarter campaign recently brought to my attention that in the latest project update, the bladeRF will soon be able to receive and decode the data transmissions from the projects satellite signals with the aid of some newly created SDR software.

In short. The program has yet to be released but the author of the program is seeking beta testers. You will need to email the author of the software to register your interest in the beta once it's ready.

https://www.kickstarter.com/projects/88 ... sts/757326

Here is the extract from the project update, as I barely know what I'm talking about, I'll leave it to the professionals.
Introducing SeeDeR

Desktop PCs are now fast enough to record and process digitized radio samples, the same way they revolutionized digital audio processing and sound editing in the 1990s. Radio operates at much higher frequencies than audio, and so requires a lot more CPU power to process. Over the past few years, a small revolution in software defined radio (SDR) has taken place. Open-source software transforms inexpensive USB TV and FM radio tuners for desktop computers into general-purpose SDR devices.

SeeDeR is the brainchild of Team SkyCube’s own Scott Cutler. It began in 2012 as an experiment to see if these sub-$20 USB SDR devices could decode AX.25 data transmissions from SkyCube’s radio. And they worked! In the 18 months since, Scott has added many features to SeeDeR - a graphical user interface with a spectrum analyzer and “waterfall” diagram, support for many more USB SDR hardware devices, an automatic doppler-shift correction algorithm, and a full-blown Windows installer.

Image
An overview of SeeDeR's GUI, by Scott Cutler

At our radio test last week, SeeDeR easily decoded AX.25 data transmissions from SkyCube’s twin, “omega”, at a couple miles’ range, using a 900 MHz Yagi antenna costing under $100. Signal levels suggest that the same system should work at orbital range. We’re not the only CubeSat team experimenting with this kind of technology: in the UK, the FunCube-1 CubeSat (AO-73) has been transmitting signals to radio amateurs around the world, who are listening with a similar USB software defined radio called the FunCube Dongle. (SeeDeR supports the FunCube dongle, by the way!)

We’re very close to releasing a public beta version of SeeDeR. To give it a spin, you’ll need a Windows PC, a USB SDR device (either FunCube Dongle, BladeRF, or RTL-SDR), and an antenna. If you’re interested in helping beta test, send Scott an email.
Looking forward to trying this out and gaining some extra functionality from my bladeRF :)

scancapecod
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Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by scancapecod » Wed Feb 26, 2014 7:09 am

Is this software a branch of SDRSharp? It looks an awful lot like it. Looks like an interesting project though.

http://www.sdrsharp.com

Scott
Scott
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spcutler
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Joined: Fri Mar 01, 2013 3:12 am

Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by spcutler » Wed Feb 26, 2014 12:28 pm

Hey guys--
Author here. It's not a branch of SDR#, although I'll grant it bears a strong resemblance! I definitely modeled the interface after SDR# since that's where I first cut my teeth in the SDR world. I don't actually share any code with SDR#, though--aside from the HW interface libraries and a few miscellaneous bits, it's all my own code.

Feel free to email me at the address in the Kickstarter link if you want to beta test. You can ask questions here or via email as well. Thanks for the support!

Youssef
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Joined: Thu Feb 27, 2014 3:35 am

Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by Youssef » Thu Feb 27, 2014 4:46 pm

That's an N'th cloning attempt. I no longer count them. The guy didn't even rename the variables. Check by yourself (while you can):
https://opendesignengine.net/svn/groundsphere/
Not only he's violating SDR#'s dsp license, but he's also violating the GPL by using code from other GPL projects. Not good.

spcutler
Posts: 28
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Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by spcutler » Thu Feb 27, 2014 5:36 pm

Youssef has contacted me privately about the alleged issue. I have attempted to work amicably with him, but he has stated that he will only contact me via his lawyer.

The opendesignengine link will probably not last much longer due to the legal issues. Although I consider the claims groundless, it's likely that I'll have to make a good-faith effort while discussions are underway.

The GPL claims are also groundless as the GPL code I used is only used in a separate library which is itself GPL licensed. Source will be distributed with the binaries upon release. This code is available now, if desired.

Youssef
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Joined: Thu Feb 27, 2014 3:35 am

Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by Youssef » Thu Feb 27, 2014 5:57 pm

"Due to legal issues" :-)

spcutler
Posts: 28
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Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by spcutler » Thu Feb 27, 2014 6:06 pm

In fact, the opendesignengine link contains code which is unlicensed for any purpose beyond our own. It was made public due to an oversight, but nevertheless anyone in possession of the full source tree is technically in violation of our rights. However, we are friendly and would not sic our lawyers on anyone (if we had lawyers).

The SDRIO libraries contain the GPL code and will certainly be made available before any public release of the program (which is currently in private testing). I will be making a separate public repository for that code. It is a hardware abstraction layer for rtl-sdr, bladeRF, and Funcube Dongle units (with more on the horizon, depending on time), and supports both TX and RX. Although we haven't nailed out the particulars, it is likely to be dual-licensed as GPL and LGPL.

Youssef
Posts: 3
Joined: Thu Feb 27, 2014 3:35 am

Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by Youssef » Thu Feb 27, 2014 6:14 pm

I think you have some trouble understanding licenses. Translating C# code to C++ doesn't magically remove the original license. It's just as illegal as linking to GPLv3 libraries via wrappers even if the wrappers were GPLv3. Consider asking the FSF if in doubt.

spcutler
Posts: 28
Joined: Fri Mar 01, 2013 3:12 am

Re: SeeDeR: SkyCube's AX.25 data transmission decoder.

Post by spcutler » Thu Feb 27, 2014 6:30 pm

Youssef has so far only provided me a single example of an alleged violation. It is a function which computes the coefficients of an infinite response filter. The code and even the variable names do look similar. That is because they both came from the same white paper on how to implement an IIR filter, which contains (mathematical) variables called a0, b0, alpha, etc. Our code shares a common ancestry and that is the source of the similarity.

The SDRIO libraries are not simply a wrapper around the rtl-sdr libraries, as evidenced by the fact that it supports multiple HW units, and further includes transmission capability.

Although I have not contacted the rtl-sdr developers recently, they have already given their blessing to the ExtIO libraries, which abstract away the API details in similar fashion.

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