I have LIMESDR, but my old pc doesn’t have USB3.0. What functions are restricted.
thanks
From my understanding, the only restriction is the bandwidth that you can sample or transmit at…
There are four things I would see with using an older PC with only USB 2.0 ports for SDR:
- Not enough power, you will need to plug a special Y shaped cable into two USB ports to get the required power (one connection is for data plus power and the second connector is for additional power). Since each USB 2.0 High Speed port is in theory rated for 5V (+0.25V/−0.60V) @ 500 mA, in theory two USB 2.0 HS ports could provide 4.4W in total if there is zero voltage drop across the cable (FYI: There is always a voltage drop across the cable, shorter cable = less of a loss).
- USB 2.0 HS has limited throughput, over 10x less than USB 3.0 so depending on how the USB stack was implemented (I’ve not tested this with a device or read through the source code) I would guess, for a single channel only, that somewhere from 7MHz(USB isochronous) to possibly 10 MHz(USB bulk) would be the maximum bandwidth possible (at least on paper, reality is probably less).Two channels half that, four channels quarter that. But since the ADC and DAC in the LimeSDR have minimum sample rates, I suspect you would be limited to one channel only.
- A PC that only has USB 2.0 HS ports probably has extremely limited processing power to handle very much bandwidth anyhow. So depending on the processing you may be restricted to processing 2 MHz to 5 MHz of bandwidth or less.I usually look up the “Average CPU Mark” for the CPU in the machine @ https://www.cpubenchmark.net . My rule of thumb is that if the CPU has a rating of 3500, then it should be OKish for most basic DSP with 20MHz of bandwidth or less. If you were only using 5 MHz then a quarter of that rating, but processing power required really does depend on the DSP being carried out. And smart application of DSP (e.g. decimate as much as you can and low pass filter in the very first block) can reduce CPU requirements.
- An older PC would also have much lower RAM bandwidth, which could also limit performance.
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i also have an older pc
without stuttering i can use 4 megs in hdsdr or 2.5 in sdrconsolev3 (needs more cpu) … its a laptop with a core2duo and with win7 64bit os
Have you tried SDRAngel. It seems to be much less CPU intensive.
yes … sdrangel does not work on that laptop cause the programmer uses some graphis functions that my laptop does not support
sdrangel may not be cpu intensive … but graphics card has to be a faster one …
it is a “business laptop” … not a gamers laptop so it just have basic graphics functions (onboard graphis so can not be changed … driver is latest)
ALL other sdrsoftware work fine (sdrsharp, hdsdr, sdrconsole v3 etc etc)
ONLY sdrangel does NOT work 
i asked programmer to change the graphics … so that any user also with an older pc can use it … his answer was “go and buy a new pc” …not what i was asking for
then i asked if he uses (needs) the fancy functions or if that functions could be changed to lower opengl version (onboard graphic of that laptop only supports opengl 2.0)
again answer was like buy a new one
i am not a programmer so even if sdrangel is open source … i can not change that graphics in sdrangel (or i would try to downgrade to lower opengl version) …
for the programmer of sdrangel that changes could be done in a short time (he knows what he has built and he also knows what he had to change) … for me it is impossible to do
i was hoping that another user of sdrangel (and a clever hacker) could do those changes and then upload it to the public … but it seems that all users have a faster pc (or a better graphics card) and no need for those changes
so sdrangel may be a nice soft … but i have to b
…
uups
sdrangel may be a nice soft … but i have to buy a newer pc
greetz sigi dg9bfc
Hi Sigi,
If you are prepared to wait a little bit, I’m sure that the server version of SDRAngel that Edouard is working towards may be helpful for you. I and a few others using SDRAngel, even though we are not necessarily programmers, may be able to help out with a simpler GUI that has lower graphical requirements. I have started to play with some of Edouards examples for his WEB API implementation. I still have some ways to go before I feel confident to work towards making my own GUI for SDRAngel, but I’m sure with help and collaboration with other members on here, we should be able to come up with something usable on older hardware. Keep coming back and check out the SDRAngel RX & TX topic for more info and updates.
Kindest regards,
Brendan Jenkins,
VK3WWB.
hello brendan
thatnk for coming back to me … yes i can wait (actually i am waiting for the gpio board and the up downmixer to expand the lime towards 10 gig and to be able to have some gpio for bands switching)
what i do not understand is … are the functions really needed in sdrangel??? or could the soft be recompiled with using instructions that it also works on low end graphics??? sdrconsolev3 is a VERY cpu hungry soft (and works fine on my laptop in 2.5 megs bw) … hdsdr works superb and if i switch off all unneeded parts in my windoze i can not only use 4 megs … it also works with 8 megs bw … so the cpu and usb bus are fast enough even for a bit bigger bw
problem is that it is a laptop and so i can not just change the graphics card … and for that intel chipset there is no better driver available …
i was hoping that the programmer (or another clever guy) could change the graphics … maybe a switchable option to use low end graphics if there is no high end graphic available?? … or just draw the spectrum a different way (like it is done in a dozen other sdr software) …???
how should the server version help me?? if i connect the lime to another pc (say a raspi3 or odroid board) and use it over network on a server app … then the graphic in this laptop still does not support a higher opengl version
???
greetz and merry xmas
sigi dg9bfc
HI Sigi,
Edouard has his reasons for writing the software as he does. I have no problem with this myself.
In regards to the server version, you would need to change to Linux to be able to use it. It can run on the same hardware as the GUI that other people (including myself) will develop. The two programs will be independent but will talk to each other.
Kindest regards and Happy Solstice,
Brendan Jenkins,
VK3WWB.
my dream is to put the lime with a sbc and touchdisplay (vu7shield) in a case (with filters, some sma relays driven from gpio, tx amps etc.) to build a multiband trx … linux will run in background (guessing that will be better as using win 10) and it should be usable in all modes on all bands (no atv or other wideband mode on shortwave hi hi)
on vhf and up i will use amp modules and for 1.2-2.4 gig i already have a 20w amp (that i now use for atv txing but only running half a watt cause the antenna is 100 feet away from shack)
best would be if it also could send and receive in dvbt and atv (with colour and tone carrier) …
ok so edouard writes a server app and you the gui (user frontend)??? and both talk to each other and can be used on the same … or different hardware?? (via udp??)
then if more processing power is needed i could just use two single board computers and split it in server and gui hardware??
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Now you’re getting the picture…