Use the WiFi Chip on RaspberryPi/Broadcom as Software-Defined Radio (SDR) | Hacker News Reader

Use the WiFi Chip on RaspberryPi/Broadcom as Software-Defined Radio (SDR)

github.com

159 pointspunnerud30 comments

It's an SDR transmitter, not receiver.

Pity that the bands are still limited to 2.4 and 5 GHz WiFi.

For GPS [1] or cellular [2] spoofing, osmo-fl2k may be a better option. In practice though, I've only used my MAIWO KCB003 for that once, as a demo. It's quite inconvenient to set up the flowgraph on an Ubuntu VM, generate 20 GB of samples, and then stream it from my Mac. Better software would make this much easier to use.

I use a MAIWO KCB003, for portability. It's not very good as a USB-VGA adaptor though, because it needs custom drivers to be installed. When the guest speaker needs to plug their laptop into a projector, they don't have time to install drivers.

[1] https://hackernoon.com/osmo-fl2k-a-15-dtv-transmitter-fm-rad...

[2] https://hackaday.com/2018/04/23/spoofing-cell-networks-with-...

The fl2k is awesome and I really wish much more would've developed around it. I guess anyone who knows enough about DSP likely already has a better radio, especially when things like the HackRF exist.

Originally posted around release 2018 (60 comments): https://news.ycombinator.com/item?id=16589703

> This projects demonstrates our discovery that turns Broadcom's 802.11ac Wi-Fi chips into software-defined radios that transmit arbitrary signals in the Wi-Fi bands.

But... what about receive?

Publish or perish license - if you use the code in your research, you MUST cite their paper.

It’s a pretty interesting license.

> The Software is not used by, in cooperation with, or on behalf of any armed forces, intelligence agencies, reconnaissance agencies, defense agencies, offense agencies or any supplier, contractor, or research associated.

It’s a nice message, but it’s not like any of entities listed above would just pass by and not use such a thing.

It’s not FOSS.

Honestly? This is hacker news. If it does what I need, I'll use it.

It's bizzare and tragic that citation changed from "here's a pointer to where I got this information" to "here's a acknowledgement of who invented this" or "this must be true because this guy published it", and finally now into some perverse form of academic (crypto?-)currency where people pay each other in citations for use of labour or codes or results or facilities or friendship or just to try to extract some prestige.

Mm..Citations as currency? Let’s add some mumbo-jumbo about blockchain and ML and go to market, baby!

In that respect, it seems the same as CC-BY

https://creativecommons.org/licenses/by/2.0/

Is it possible to get a workeable sdr that can send and receive for $100-200 these days? If so what frequency bands would it support?

The Pluto SDR for students that Analog Devices puts quality assement failure SDR transceivers in are in that price range. You get 325 MHz to 3800 MHz frequency tuning range and about 4 MHz of usable bandwidth. The software ecosystem isn't great and the default rx/tx drivers have a lot of overhead. There are also hacks on the software and hardware side to improve tuning range and other aspects.

And of course there's the HackRF for 10-6000 MHz @ 20 MHz bandwidth Tx or Rx half-duplex. The software ecosystem is now amazing and the hardware clones are relative cheap. But all HackRFs are pretty deaf and full of spurs and images.

Check out LimeSDR for an affordable full-duplex SDR. 200 EUR IIRC.

Is there some secret to getting a Pi at MSRP or is it just another victim of the semiconductor shortage? I can't find a Pi Zero W for under $20 or a Pi 4 for under $50.

I've heard that Microcenter is a good option. They seem to be the best bet right now for things like GPUs if you go on the right day (with a bit of luck).

Stock and prices are fine here in the UK right now.

Check out the dealers on the Raspberry Pi website. A few of the dealers have them in stock and they appear to be close to MSRP. (I'm waiting on a 4 GB unit that was about US$56, compared to US$55 MSRP. The 2 GB units at US$35 are listed as well.)

Thanks for that. I had only checked a couple of them on the list but your comment encouraged me to check them all, and I found a source in stock.

Adafruit.com has the Zero W and Pi4 1GB and 8GB at MSRP, and I wasn't aware of big shortages of the OOS models (2GB and 4GB). They just come and go. There is a qty 1 limit for the available pi4's right now though, which has not always been in place. The Zero and Zero W have always had a qty 1 limit everywhere, since they are sold at near breakeven or at a loss.

Try also sparkfun.com. Sparkfun and Adafruit both have a "notify me when back in stock" feature where they send you an email if and when the item becomes available. That works pretty well. If something is in short supply it tends to sell out fairly quickly (like within days or hours), but it's usually not so intense as to sell out within seconds. So if you check for the item as soon as you receive the email, you can usually get one.

This is why Broadcom chips come with proprietary blobs: the FCC and corresponding regulatory bodies elsewhere would never approve them if they had open source firmware or were fully documented.

Source? This seems unlikely considering the existence of legal SDR.

Also proprietary blobs seem like a whole separate thing that companies would do to protect IP.

Can confirm. Look at the FCC regulations for selling rf-emitting devices. The seller has to show that the device will only emit at the specified frequencies and power. When it's consumer-facing, like a wifi router, one way to do that when the hardware itself is technically capable of more, is to lock down the firmware.

The downvotes on gp are misinformed.

These chips and their closed blobs are older than the relevant FCC regulation.

Hasn’t the relevant fcc regulation (concerning signal strength and use) been around since the eighties at least?

It was a 2015 ruling that can be seen as not allowing user modifiable firmware for transmitter hardware. https://www.wired.com/2016/03/way-go-fcc-now-manufacturers-l...

I've seen this same argument about cellular modems too, and that, too, has never prevented people from reverse engineering them.

In a very limited set of mobile baseband radio chips, it's a massive undertaking. All that's around is OsmocomBB(A few 3G chipsets) and FreeCalypso(One discontinued Texas Instruments 2G chip), both of which I believe were built off leaked code. The main developer behind FreeCalypso has found a Chinese supplier still producing the TI chips though, so it lives on.

Do you know anything about the future open-source modems? Most promising project I've seen is working on the PinePhone modem https://linuxsmartphones.com/hackers-develop-open-source-fir...

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