Well, that was fast! Last week, we reported on two apparently simultaneous hacks using the 2.4 GHz radio inside many ESP32 variants that enabled raw access to the radio samples, turning it into a listen-only software defined radio (SDR) platform. Listen only? That’s only half of the SDR story.

Last weekend, [marble] got started fixing that, and released an early early version of ESP32 firmware that can also transmit, and got it working with gqrx. The demo communicates between an S3 and a C6 using a Hellschreiber mode, something that’s certainly out of the WiFi spec. And it didn’t stop there, either. [marble] is working on 802.15.4 modulation at the moment, which means that maybe soon your ESP32 will speak ZigBee.

This is all in the roughly 2.4 GHz band, but [marble] suggests that it might be good down to 1.8 GHz. (Editor’s note: previously, we said 100 MHz, but that was incorrect.) So there is still some uncharted terrain, and it’s clear that the boundaries on the ESP-SDR are just starting to get pushed.

If the early hacks on the RTL-SDR set off a wave of hacker SDR radio experimentation, and we can only hope that this is the beginning of the ESP-SDR era. Thanks then to [marble]– and the original hacks coming from the Espargos team for kicking this all off!