Thread

Various Projects Find Hidden SDR Capabilities in ESP32 Microcontrollers

288 points · 67 comments · nkw

mallets · 1790879919 · focus · HN ↗
So many $1 wireless ICs have a powerful "SDR", but will never be documented due to certification/compiliance/export-control reasons. The projects listed here rightly limited the scope to RX-only but Espressif might be forced to "patch" this away if arbitrary TX too is possible (or starts making headlines). Hope it doesn't come to that, more cheap options for RF-to-bits is always welcome.
On a technical note, not much I can find about the signal quality. Phase noise, images, DC Offset, etc. Have to get my hands on one, ESP32-S31 seems promising.
1. ErroneousBosh · 1790880388 · focus · HN ↗
  > The projects listed here rightly limited the scope to RX-only but Espressif might be forced to "patch" this away if arbitrary TX too is possible
  Why would they? It's perfectly legal to operate radio transmitters on any frequency you like, if you hold a suitable licence.
  1. ssl-3 · 1790883444 · focus · HN ↗
    It is legal for a person with an appropriate license, yes. But laws (in the US) about RF transmission differ from how many other laws are structured: We're only allowed to transmit what we have permission to transmit -- and by default, we're forbidden.
    But right now, I've got an ESP32 WROOM module on a dev board sitting in my windowsill reporting some sensor values over wifi.
    The WROOM itself is registered with the FCC[1]. If I stick to using the documented operation, then I have permission to use it in those documented ways. As a practical concept, I don't need a unique license to use it in the way that I am; I'm granted the ability to use it by Part 15 of the FCC rules.
    And that's pretty great: The hardware was inexpensive to buy and very easy to find. I was able to spin this sensor up very quickly and get moving on the software side that deals with those readings. It has been a very rewarding little project with a fantastic cost:benefit ratio.
    The fear being expressed here (which I don't necessarily subscribe to) is that things like this WROOM module will become less-available when/if methods to use it in undocumented ways are published and start becoming used.
    [1]: <a href="https://fccid.io/2AC7Z-ESPWROOM32" rel="nofollow">https://fccid.io/2AC7Z-ESPWROOM32
    ErroneousBosh · 1790887225 · focus · HN ↗
    The FCC is relevant in exactly one country in the world.
    zoobab · 1790940652 · focus · HN ↗
    I created a new country Zooland where there are not RF regulations:
    <a href="https://www.zoobab.com/zooland" rel="nofollow">https://www.zoobab.com/zooland
    For the same reason, those regulations (FCC radio lockdown etc) stifle innovation in the SDR world.
    skinfaxi · 1790945919 · focus · HN ↗
    Is not some regulation necessary? Spectrum is limited. You seem to have thought a lot about this so curious about your perspective.
    smallmancontrov · 1790949868 · focus · HN ↗
    Spectrum used to be a lot more limited when frequencies had to be exclusive and baked into hardware designs. Now we have agile radios that can tx/rx across wide bands and dodge other peoples' traffic, so the motivation for exclusivity is a lot weaker. If you walk around with a spectrum analyzer you will see traffic voting with its feet and overwhelmingly choosing the free-for-all ISM bands because dodging other peoples' packets is easy compared to obtaining spectrum licenses around the world.
    So: the optimal regulatory approach changed, the laws didn't keep up, and now we have suboptimal regulation that isn't bad enough to spur a fix and vested interests (spectrum owners) who don't want it fixed so I expect it to continue for a very long time. So it goes. It's not great but if all the world's problems were as small as this one it would be a much nicer place.

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