Hardware hackers found secret radio capabilities inside the cheap ESP32

Hardware hackers discovered that the ubiquitous ESP32 microcontroller houses undocumented capabilities that allow it to act as a Software-Defined Radio.

Multiple projects independently found that several ESP32 chips can bypass their fixed WiFi and Bluetooth hardware to capture raw radio samples directly. The ESPARGOS team showed the chips can tune into frequencies from 2.2–2.7 GHz (and up to 6.0 GHz on the ESP32-C5) at sample rates up to 80 MS/s. Meanwhile, other developers are using the feature to build 5.8 GHz drone video receivers and stream radio data using external FPGAs.

Why it matters: The discovery turns a dirt-cheap microcontroller into a flexible tool for analyzing radio signals without extra tuner hardware. While standard ESP32 boards can only export short data snapshots to a PC, newer variants like the ESP32-S31 can stream continuously over Gigabit Ethernet at up to 16 MS/s.

If you want to test it yourself, the ESP-WebSDR tool lets you flash the firmware to most ESP32 boards directly from your browser to view a live signal waterfall.

Turns out the chip you bought to control a smart lightbulb was a radio scanner all along.