ESP32 and LoRa chips found hiding usable SDR capabilities

The radio inside the inexpensive ESP32 microcontroller can apparently work as a software-defined radio, and it may not be the only everyday chip with that talent. Hackaday reports that several experimenters, some working independently, have unlocked raw radio access in parts normally sold for Wi-Fi and LoRa links.

According to Hackaday, the trail began when [Espargos] and [h0m3us3r] each found a hidden debug mode in the ESP32 family that exposes raw IQ data from the 2.4 GHz radio. Normally that radio hands its signals straight to the chip's networking hardware, so the IQ stream had been out of reach. For newer hams, IQ data is the raw sampled signal that SDR software such as GNU Radio works with, so access to it turns a fixed-purpose radio into a general-purpose one.

Transmit followed quickly. Hackaday credits [marble] with getting the ESP32 to transmit and tying it into the standard osmosdr data flow, which lets a large body of existing SDR tools use it. The outlet says [jochenhammes] and [z1000biker] had their own transmit-capable versions running at about the same time, and that people have already sent digital TV, voice and FM Hell signals with the hack.

A second find may matter more to VHF and UHF operators. [Samson1te] reported SDR access in the LR2021 LoRa chip, which Hackaday describes as offering 16-bit resolution and coverage from 150 MHz to 960 MHz. That range takes in the 1.25 meter, 70 centimeter and 33 centimeter amateur bands, while the ESP32's 2.4 GHz radio sits near the 13 centimeter amateur allocation.

Hackaday compares the moment to the early RTL-SDR days, when cheap USB TV dongles turned out to be capable receivers and spawned a wave of software. The writer expects many more projects in the coming months.

Hams who experiment with the transmit side should keep it inside their license privileges and the amateur bands, and remember that a hacked chip makes no promises about spectral purity. Checking the output on a spectrum analyzer or a second SDR before putting it on an antenna is cheap insurance.