3 ms·
> Wouldn't this invalidate the FCC certification on the prebuilt modules? MAC is at OSI Layer 2. FCC concerns about radio power occur at the PHY layer, OSI Lay
by throw0101b 3y ago
> Wouldn't this invalidate the FCC certification on the prebuilt modules?
MAC is at OSI Layer 2. FCC concerns about radio power occur at the PHY layer, OSI Layer 1:
> On the ESP32, the PHY layer is implemented in hardware; most of the MAC layer is implemented in the proprietary blob. One notable exception to this separation is sending acknowlegement frame: if a device receives a frame, it should send a packet back to acknowledge that this packet was received correctly. This ACK packet needs to be sent within ~10 microseconds; it would be hard to get this timing correct in software.
* https://pics.zeus.gent/vYXyQm2t9pJCzpDdWFvq9oWR2DACoUJoTsYf8qiz.jpg https://pics.zeus.gent/vYXyQm2t9pJCzpDdWFvq9oWR2DACoUJoTsYf8...
- calamari4065 3y agoHuh, neat!
- crote 3y agoIt's not that simple. Besides implementing a SoftMAC, the blob is also responsible for setting up the PHY, so it would definitely be able to adjust things like transmitting power. See the part describing `esp_phy_enable()`.
- rkfjrjrkfnrkd 3y agoIf you know where to look, I'm quite sure you can already do this with vanilla ESP-IDF. I don't have a VNA or whatever is used to measure power at the antenna, but I do have a precision ammeter that confirmed my changes were effective at the supply. I only changed PHY power parameters and a lot more power was going somewhere. Also, in my limited understanding, even changing the physical antenna can alter transmission power characteristics in such a way that it likely violates some limit, at least for some very specific wavelength or direction.