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"Turn any raspberry pi into an SDR" ... by adding hardware to it. The headline made me at least think it somehow uses the pins as antennae, also because people
by Aachen 5y ago
"Turn any raspberry pi into an SDR"
... by adding hardware to it. The headline made me at least think it somehow uses the pins as antennae, also because people have done this sort of thing in the past.
- tinus_hn 5y agoThe interface having enough bandwidth to do this is interesting
- Aachen 5y agoAh, I did not know that. I've always worked with USB SDRs, is a regular USB3 higher bandwidth than these pins?
- blihp 5y agoUSB 3 can provide orders of magnitude (how much depends on which rev) more bandwidth. This device provides slightly more bandwidth than an RTL-SDR stick over USB 2.
- jcrawfordor 5y agoUSB2 can do 10MSPS easy, but in my experience small SBCs like the Raspberry Pi struggle to keep up with this rate at the CPU. Might be more practical with the newer models, but I gave up on an RPi 3 with a 10MSPS SDR because it was excessively dropping samples at around the 5MSPS point... so it's possible that 4MSPS is approaching the limit of the CPU, at least for a given level of optimization of the software tools (I was mostly just sending out I/Q samples over the network).
- dragontamer 5y agoIt seems to only support 4 Mega-samples/second, which isn't much bandwidth. EDIT: Its a fair bit of bandwidth for an embedded system like Rasp. Pi, so I'm not trying to undersell the project. But we're looking at 32-bit samples at 4MSPS, or ~16MB/s bandwidths here.
- GekkePrutser 5y ago32-bit samples is a lot for an SDR though!
- gswdh 5y agoIt’s one or two 13 bits samples from the ADC padded out to 32 bits. True 32 bit ADCs do not exist.
- robocat 5y agoFrom article “each ADC sample contains 13 bit (I) and 13 bit (Q), that are streamed with a maximal sample rate of 4 MSPS from the AT86RF215 IC. This channel requires 4 bytes (samples padded to 32-bit) per sample (and I/Q pair) => 16 MBytes/sec which are 128 MBits/sec. In addition to the 13 bit for each of I/Q, the Tx/Rx streams of data contain flow control and configuration bits.”
- gregsadetsky 5y agoSame. Here's a Pi-based FM transmitter that uses no additional hardware except for an antenna: http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...
- dTal 5y agoNote: do not use this. The carrier wave is a square wave which means you spill ungodly amounts of RF into harmonic sidebands. If you dare to plug this into an amplifier - at least without a lowpass filter - expect a firm knock on your door.
- klysm 5y agoIsn’t the point that you use this without an amp though
- dTal 5y agoIt's still illegal (and possibly dangerous) even without the amp - you're just much less likely to actually interfere with anything because the range is short. But you still shouldn't use it.
- klysm 5y agoOut of curiosity, what laws does it violate?
- SV_BubbleTime 5y agoAll manner of jamming and FCC broadcast rules.
- klysm 5y agoYeah but specifically, I just don’t know anything about these laws and it seems fine to be doing it at low power
- djmips 5y agoIt's pretty tightly integrated so I give it a pass. I like the design a lot.
- stefan_ 5y agoThey are doing 500Mbit/s over these pin headers, don't worry they are a freaking antenna all right.