Open Research Institute Presentations, 13 Jun 2022

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From YouTube: Evariste Courjaud PlutoSDR and FPGA

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Hello: everyone, I'm everest, f5, oskar ikovoska, I'm a ham radio operator since 1986.

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I work in a digital tv for about 15 years, I'm a software developer, mainly in c c, plus plus language.

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For today I tried to share you my experience around the crypto sdr platform.

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That I work now uh for three years. Okay. So, let's begin uh between the last conference uh around the five years ago, at sdr academy, I presented the app here tx, which is a low cost transmitter using the raspberry pi gpio.

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The project is still alive and hopeful.

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Hopefully there is some contributor like uh gm fritz, which has, for example, a new radio block for that and it's very cool, um I'm a more a hacker than a dsp guru and my mathematical skill is not always at the top, which I so I'm mainly focused on the hardware uh specific feature between uh vs uh magnostic uh software, which means that there is already some very good pc software, uh like sda angel sdr console as the approach plus etc, and I I mainly uh focus on what feature we can do uh with the pluto sdr.

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So it is more focus on the embedded platform than the usage with the pc with that. The target is to, for example, remove some bottleneck, which is the usb bandwidth of iq, but we can do also some dsp offloading, for example, make the fft on the pluto itself make some modulation demodulation, and we can also target some standalone news using, for example, the gps to record a spectrum.

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And of course we have some custom. Applications like the atv here is, for example, my setup for the embedded pluto. It is uh uh composed of a battery pack, uh which I'll put the five volt inside the pluto and also on uh a usb hub on the usb hub is plug memory.

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Stick, for example, for arc buying iq signals, and but we have also a wi-fi access point in order to discuss with uh output, well external uh peripheral than like the pc or the phone, and we have a cheap gps inside, but we can add other components like a usb audio or usb video.

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Just a quick remember for the pre-tourist year, because there is a lot of documentation on that and already some very good presentation.

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So, just to remember that there is uh adcdac zinc, which is fpga and armed cpu, and there is some flash memory in order to uh to contain. Well the system, the linux system, the bitstream of the fpga and some softwares around all that.

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So what is exactly a firmware? Well, it's u-boots! So it's a bootloader in order to load the the firmware itself, which is contained on flash.

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It's not covered here, the linux systems with some drivers, some ips stacks and the fpga bitstream, which could be custom, of course, and above all, that some softwares, uh the discussion with external words, is through usb or source or ethernet or wi-fi, for example,.

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Let's start with the deep state which is the fpga, so the fpga side is done using some tools from xer lines, so we use vivaldo for the zinc 7010.

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We mainly had some components on the graphical side, but we can also use some tcl scripts in order to be more portable.

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I'm not a vhdl caller, so right now, I'm focused on integrating some ip from xylems or from other, like horsekemp, ahri, etc. So what we can do with that?

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Well, first, we can offload some process, which is very time consuming even on the pc or on the arm of of the p2.

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What about adding uh fft uh in order to have uh the power? uh Well, the spectrum power um we can. We can use and- and then you can, you can uh send some spectrum with uh well less bandwidth to a web, socket for example, or to uh to average it on the pluto itself. Before sending ink sending it to a other process, we can have some interpolation decimation customized, which means that on the official firmware, it's it's only interpolated by eight and uh for some application we need more than than that.

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So we have exactly the bandwidths we want in order to have less bandwidth on the usb or on the ethernet.

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We can have less dynamic, normally the are on 16 bits, but we can choose to have just habits like the rtl sdr, which means that we have less dynamic but more bandwidths going through the usb.

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In the control we can also choose to have a c float in order to to have no power on cpu to convert integer to cflot. We can have also some ip very interesting ip. Like dvds do modulator, we will talk it later.

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We can add some sample time, stamping which, which could be required for telephony application, and we can integrate other ip like mixer, etc, and all the all is um well a kind of what idea you have.

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Okay. Next is the stage of linux. um We can customize some drivers on the linux compared to the official vmware. First, we can say that the pluto is recognized as a sun. God. uh How why? Why would you know we do need that is, for example, to use software uh well, for example, uh some digital mode software using software like ws, gt, fldg,.

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As the pluto is recognized with this driver as 48 kilowatts audio cards, you don't have to run an external sdr software and you don't have to mess with the virtual audio on the pc. All is done. uh The demodulation is done directly on the on the pluto and over the usb. It's only audio baseband.

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We can add some ethernet on usb adapters, which means that not all the usb adapters are supported on the official firmware, so we can add it. We can add video for linux who to have some usb video inputs. We can have audio inputs also with that, for example, we can build a complete standalone transceiver with microphone and headphone directly on the pluto and don't have any other components like pc.

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We can add gps and we can customize some driver, like the analog device adc to fork it and and say that the pll go to is down limits which is 47 megahertz instead of uh 71 megabits, as I remember so with this with this 47 megas, and if we have 60 mega sample uh divided by 2, so we have 47 minus 30, which means 17 megahertz signal minimum, which is the low frequency for pluto.

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Okay. Let's next is the upper layer, which is software. The software use, for example, use the linux drivers and also the component of the fpga design. So this is what I call a sweep fft, which is a white band. Receiver- spectrum receiver: you don't have you, you can't demolate demodulate a signal in that, but you can easily see what's happening on a wideband spectrum.

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There is, for example, this is a 200 megahertz span where we can see some telephony transponder. We can see on the waterfall that there is uh also a uplink from my phone.

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uh The this is possible because I use the quick or fast lock tuning and with these methods we can tune from one frequency to the other, only in about a few hundred microseconds instead of few milliseconds when you use the usb and io library.

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So there is some drawbacks here on that is that, as we tune at each time, 40 megabits.

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At each step, at each frequency we also sample the third fifth and seven and etc harmonics. So we can have some areas um because there is no uh upfront filters. uh There is uh some solution in software to try to remove some ill aliases and it is a work in progress.

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Here is what it's show when you run it. So this is a 40, sorry 60 hundred megahertz span, and you see that it's quite dynamic and it is just running on a web piece on a web browser or even on the phone here. We can see that there is some broadcast fm station at the left and some television transponder gsm emts at the right.

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Okay, so now how to discuss with this standalone equipment? Well, we can use a very popular protocol, which is mqtt.

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It is very popular in internet of things and in dometic. So there is a lot of software developed around that this protocol is very simple and uh quite quite powerful, because uh very uh well, very popular, uh so the control and the statues are done without knowing the library specific to the pluto. So it's just uh some very easy message to send.

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This message could be done could be sent by some very small devices like arduino or some some web application, and with that you can add some peripheral call, for example, knobs or little lsd, lcd displayed.

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And all is done uh very easily with that. Here is um a software which is mqtt control which doesn't know anything about the pluto. But you can see here, for example, the rsi, along with the time the iq samples are not sent through mqtt, because it's not a high bandwidth protocol and it's done through udp or web sockets.

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Here is an example of a graphic application done by po2g kio. It's done on a raspberry pi and just using the mqtt control and status to the atv application.

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Another application is recording the spectrum and recalling the position at the same time and then try to display it, and here I just uh take my car and uh walk around, and there is some dvd um terrestrial television and we can see that we have the rf coverage of the sun of this station, but we can use it to uh maybe have an antenna pattern.

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uh This is a proof of concept. I think that there is a lot of things with that.

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Now it is a dvb-s2 receiver.

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Normally the receiver is done using a hardware called mini tuner which run on minitune, which is on on a windows, and here the minituner is plugged directly on the usb hub of the pluto and it used the longmind linux software, which is forked to to work with mqtt, and with that here the telephone. The phone is just getting the transport stream video through the wi-fi.

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And adjust the vlc application on it.

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This is a particular dvbs2 modulator. The dvbs2 modulator is normally done in on the software part on the arm, but thanks to open research institutes, there is a fpga iep for that, and that's quite interesting because there is no cpu at all usage and we can perform some very high symbol rates with that, for example, here we have 15 uh mega sample and theoretically we can go up to 40 mega symbols. So a lot of bandwidths to send video or datas.

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There is a datv firmware I developed two years ago, which is now very popular for q100dv uplink, because it's a complete firmware, so you have the dbs2 modulator, some transport stream mix, some video encoder, some analyzer and thanks to a contributor for the web interface, it is quite easy to uh to use here is, for example, the transfer stream analyzer of of station.

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There is a lot of future plans like making a vne, well a vector network analyzer with the pluto revision c, but we can also add some other modulator like the ab. We can have more some security proof of concept like iq replay attack, but the list is very long and just needs to contribute to uh to have more like that.

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So improving depends on audience.

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uh The goal is to have several uh several stage, which means that first, the firmware is already built with all the tools I present here and the goal could be to build some custom mqtt clients, depending on the application or web interface, for that second stage could be uh for software developers to use some github application and try to uh transfer it to the to uh to the pluto, and it's just an arm cross compilation and the third- and it's not very easy.

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So I think that two days training could be a good thing for people who want to understand all how we can. We can customize the fpg design and how to build the complete firmware in order to to make some custom solutions.

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I'd like to thanks analog devices for some hardware samples.

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Because we spend a lot of times on bill roots and it helps me a lot nuts and granule for the fpga side and, of course, open research institute for the dbs ii fpga.

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uh So you can have my contact here. Unfortunately, I have not I'm not available to answer questions at this time. Sorry go to paragliding.

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Thank you very much for listening to me and do not hesitate to contact me and ask me some questions. Bye.