Hello everyone, I was asking if limesdr is able to run in a standalone mode. The answer seems no. I am quite interested in which host can be/have been used.
Please feel free to add the host that you are using in this post. If possible, please also list your development tool.
Some answer from my previous post: tablet, raspberry pi, Odroid-c2.
Thanks.
If youāre like me, you probably just want to turn it on with the settings automatically uploaded to the device?
I use a laptop. My guess is that you want something that can stand alone and also be somewhat autonomous. But I can only guess since you havenāt told us what your constraints are.
Laptops have a built-in battery backup and are quite cheap
Etc.
Sorry I should have put more information in the initial post.
I am working on a university research project and we are planning to build a network with several LimeSDR boards (e.g., more than ten). The purpose is to carry out experiments and collect real data. Each node may run several minutes, one hour at the maximum, 24/7 is not required, so I presume the data collected wonāt be too much.
My plan is using some host to control the LimeSDR and store the data. I will then transfer all the raw data to the laptop for further processing. I want to use some cheap host (cheaper than a laptop).
My concern is how to store the data for further processing. Do you have any advice on this?
Odroid XU4 or UDOO X86 sounds like perhaps the best candidates in terms of price/performance and size. Provided they have sufficient processing power for your given application.
I donāt have an XU4, but Iām tempted to order one to try it out with LimeSDR. Still waiting for my Kickstarter UDOO.
Hi all.
I have a similar need: will run 24/7 unattended, headless and recording radio astronomy data.
Even if Iāve used R-PI-3 until now for other SDRs, I would not be able to use LimeSDR at a sampling rate > 2.4M using the USB 2 port of the R-PI. I already hit that same threshold with simple RTL-SDR donglesā¦
R-PIās USB and ethernet go through the same USB host chip so perfs in some scenarios are not ideal.
So Iām interested in the host selection looking at both USB 3 presence, fast ethernet port, proper CPU perf, RAM availability and compatible OSs (my pref is for Debian ).
FYI: thereās a post by @g8sqh mentioning some specific issue on the odroid xu3 and xu4. They could be of some importance to some users depending on the planned usage:
Lotās more info in that same thread:
thereās @martywittrock mentioning heās using an MSI Cube PC.
about the usable sampling rate @Kc7noa writes he ācan run 3Ms/s with no decimation on an Odroid-X2 AND Odroid-C2 ā¦ā
@g8sqh also mentions the ethernet speed available depending on the board, 100 Mbps vs 1 Gbps
finally, just yesterday I was looking at UP boards http://up-shop.org/4-up-boards
they seem to have nice specs but still have to read everything.
Does anyone here have an UP board in use with LimeSDR ?
Iām also considering power needs, selecting the lowest possible in my case and not an easy topic when you also want a fast cpuā¦
mario
Hummm ā¦
I can do 4,500,000 sample rate @60mhz lpf on my Odroid-x2 ā¦ Shurly a UX3 can do better ā¦
mario
No question that an ARM board will have better CPU/mW than Intel x86. I abandoned my XU3 as a standalone system (with HDMI display) since thereās a long-term unfixed bug on the X server, and gqrx hit that bug immediately. For this the XU4 should be the same
Running headless I had no problem with CPU upto 15 Msamples/s, but on the XU3 the ethernet is off USB2, so only 100 Mbps. Not sure when that would become a bottleneck for X windows exporting drawing commands. On the XU4 (which is the one you can still buy) the ethernet is 1G, and on one of the USB3 - the other goes to a socket - where you attach the LimeSDR.
Remember the XU3/4 CPU is 4 2.0G ābigā cores and 4 1.4G ālittleā cores. As long as your processing can use multiple cores, then the XU3/4 is a powerful machine for its DC power requirements.
With the XU3/4 you also need to factor in the cost of the eMMC ādiskā module - they are much faster than microSD, and youāll one to get best performance from the Odroid. If youāre doing any serious system-level work I strongly recommend also getting the serial console to USB cable - that way you get access to the u-boot loader and console messages before the screen is booted up.
I may have time next week to see how fast a sample rate the XU3 can handle headless - for you my question is how much processing do you do on the XU3/4, and what is the data rate you need to record, and is that to be recorded on the XU3/4? Modern hard disks over USB3 will sustain (linear) write speed of say 150 Mbytes/s, so you might be able to record 30 Msamples/s quadrature directly on an XU3 - which has 2 USB3 channels brought to 2 sockets. Only problem is you canāt then get the data back over ethernet! On the XU4 you canāt do that trick - you would have to process the data to a lower rate before recording it either to local USB disk (shared with the LimeSDR data) or to remote storage (limited to 1Gbit by the ethernet)
Good luck with the astronomy
āDavid
I quite like the idea of an XU4 + LimeSDR with SoapyRemote and the actual application running on a remote PC. Did this before with an Intel NUC running the server ā worked well, but brutal on the LAN 
Does anyone also have experience on using tablet as the host?
I understand the cost may be higher, but will it be easier to use?
Any comment is welcome.
Do many tablets have USB 3.0? My guess is they would be the least easy to use when compared with a desktop or laptop.
Maybe a stupid question, I presume the USB interface affects how fast the LimeSDR can write the data to the host. So if I donāt have a high requirement on this, USB 2.0 will do. Right?
I think you can use usb 2 with LimeSDR running not at the top sampling rates.
Some additional thoughts: if a tablet has USB-C connector it should support USB 3.1 speed.
Iāve also used my Android phone with a specific app to read rtl-sdr iq stream but a specific driver has been developed and released in order to manage rtl-sdr dongles on android via usb otg cables.
I believe theoretically this could be done as well for LimeSDR but some consideration should be done also on the processing power of the tablet. I meanā¦ should usb-c otg at full speed allow streaming from LimeSDR at max sample rateā¦ the data should still be processed by a cpu capable of sustaining that loadā¦ some sort of compromise should be met.
About power on usb otg cables:i believe itās bidirectional and LimeSDR could receive power from the tablet. Not sure if that could be enough or how much the tablet battery could last.
My 2 centsā¦
Mario
@g8sqh
I plan to do experiments at different wavelengths.
For example Sun and Jupiter-Io at 15-30 MHz and hydrogen line around 1.4 GHz.
I donāt need to save the raw IQ stream. I would process that on the selected board cpu to get just fft values and store the resulting fft bins at regular time intervals doing scans over a certain bandwidth.
This lowers my needs in terms of local storage speed. Yet I would prefer having a good cpu to run fftw routines possibly in multi threading on some cores.
Iāve already modified and successfully used rtl-power-fftw in its multithreaded version on the r-pi.
I see there is now soapy_power available and I would like to use it in the same way with limesdr.
When I use large integration times speed is not so important. But when I need to see details with lower integration times the cpu speed becomes the bottleneck.
Itās my understanding that currently the fpga on limesdr is not involved in the fft production. Adding that function to the fpga firmware could represent a huge step for my usage scenario but also for those interested in using limesdr as a spectrum analyzerā¦
A quick look for benchmarks suggests a XU4 is perhaps twice as fast as the Pi 3 http://www.cnx-software.com/2016/04/02/low-cost-development-boards-linux-benchmarks-raspberry-pi-vs-banana-pi-vs-orange-pi-vs-odroid/
Iām sure youāve already met libfftw - but you need to make sure you have a version compiled to use the NEON instructions for best floating point speed. Also remember to run fftw-wisdom - it takes many hours CPU, but further optimizes FFT speed.
As for running on the FPGA - that would be wonderful, but I can see immense difficulties:
Altera have an FFT library, and it can be run on cyclone IV (our FGPA) https://www.altera.com/en_US/pdfs/literature/ug/ug_fft.pdf
Good so far, but then
1 Iām not on the dev team, so I have no idea how much of the FPGA is unused after it has taken data from the radio and sent to the USB
2 The Altera code is heavily licensed, and likely to be expensive - like thousands of $$. I think I found the relevant item on mouser item 989-IP-FFT - it is listed at Ā£6,483.79 or about $8000 US - and you may need the standard version of Quartus ($2995)
So, unless there is any open-source IP for FFT on altera devices, thereās no way we can get FFT on them without a lot of investment, or a lot of code development. And there may not be enough FPGA spare anyway - the FFT in the user guide gives figures for cyclone V, and it would be a good fraction of our 40K element FPGA. I suspect you first need to see what an XU4 can give with the software tuned for that ARM chipā¦
Good luck
āDavid
Hello David and thank you for the precious info.
I will certainly have a look at those benchmarks.
Yes, I know libfftw but I never used fftw-wisdom : will search and read the docs.
Yes, I knowā¦ FFT on the FPGA could stay a dream for some time and for sure I would start with squeezing the most out of the host cpu.
regards,
mario
If you look at a some of the Opencores for Verilog FFTās:
64 point fft/ifft - Overview :: Pipelined FFT/IFFT 64 points processor :: OpenCores
128 point fft/ifft - Overview :: Pipelined FFT/IFFT 128 points processor :: OpenCores
256 point fft/ifft - Overview :: Pipelined FFT/IFFT 256 points processor :: OpenCores
OK the above listed resources are for a Xilinx FPGA, and not Altera FPGA used in the LimeSDR, but for simplicity sake if you consider each CLB (configurable logic block) as being a LAB (logic array block), you can see that a FFT does require a lot of resources, the question is how much free resources exist in the LimeSDR FPGA chips ?
LimeSDR-USB - EP4CE40F23C8N (Cyclone IV E 2475 LABs 39600 LE 1161216 RAM(bits) 328 IOs)
LimeSDR-PCIe - EP4CGX30CF23C7N (Cyclone IV GX 1840 LABs 29440 LE 1105920 RAM(bits) 290 IOs)
Iām sure that some public FFT core could be adapted and squeezed inside the existing FPGA, but I suspect that the FFT size for 12-bit samples would not be very big at all. I would love to be proven wrong though.
Yit would be wonserfull if the fft and I/Q correctiin could be done on the fpga ā¦ that should decrease the USB bandwidth loadā¦
@andrewback Hello Andrew, does my above comment make sense? Will LimeSDR work with USB 2 (with a lower data rate)? We are having some Zedboard with USB 2.0. I wonder if I can use them to host the LimeSDR. Thanks.