ESP32 Firmware Adds Experimental Transmit Capability to an SDR Hack
Reading lead
Developer Murmel has released an early version of ESP32 firmware that extends recent work exposing raw radio samples from the 2.4 GHz radios in some ESP32 variants. The earlier hacks provided listen-only software-defined radio functionality; the new firmware can also transmit and has been demonstrated working with gqrx. In a demo, an ESP32-S3 and ESP32-C6 communicate using a Hellschreiber mode devised by the developer. Work is also underway on 802.15.4 modulation, but the article describes that as in progress, not as a completed ZigBee capability. Espressif’s API reportedly indicates tuning as low as 100 MHz, though the article cautions that the radios’ filters may make operation there ineffective. This remains an early experiment, with no broader performance measurements or confirmation of reliable operation across ESP32 models provided.
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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, [Murmel] got started fixing that, and released an early early version of ESP32 firmware that can also transmit, and got it working with gqrx. He demos it by communicating using a Hellschrieber mode of his own devising between an S3 and a C6. And he didn’t stop there, either. He’s 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 Espressif’s API suggests that the radios will tune down as low as 100 MHz, although we can hardly imagine that the filters are tuned to make that particularly effective. Still, 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 [Murmel] – aka [Marble] – and the original hacks coming from the Espargos team for kicking this all off!
Source: Elliot Williams ·Hackaday · 2026-10-13T20:00:21.000Z · Read the original article
Why read this
The concrete advance is an early firmware demo of ESP32 radio transmission, including S3-to-C6 communication; 802.15.4 remains in development, and performance or broad compatibility is not established.
AI score 55 · View scoring rationale
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- gpt-6-luna-2026-09-22 · 53
The concrete advance is an early firmware demo of ESP32 radio transmission, including S3-to-C6 communication; 802.15.4 remains in development, and performance or broad compatibility is not established.
- deepseek-flash · 58
Adds transmit to a previously listen-only ESP32 SDR hack, a concrete hardware capability change with a working gqrx demo, but it is an early build without independent validation and limited to the 2.4 GHz band.
Analyzed: 2026.10.14 03:14 UTC
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