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Various Projects Find Hidden SDR Capabilities in ESP32 Microcontrollers

288 points · 67 comments · nkw

  1. mallets · · 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 · · 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 · · 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:&#x2F;&#x2F;fccid.io&#x2F;2AC7Z-ESPWROOM32" rel="nofollow">https:&#x2F;&#x2F;fccid.io&#x2F;2AC7Z-ESPWROOM32

        1. ErroneousBosh · · focus · HN ↗
          The FCC is relevant in exactly one country in the world.
          1. TeMPOraL · · focus · HN ↗
            Other countries have equivalent organizations and they all tend to be in sync on this stuff.
            1. mmmlinux · · focus · HN ↗
              Not true. In some countries you can be prosecuted for just receiving signals.
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