LR2021-SDR is an open-source project by Samuel Reynolds (SAMS0N1TE). It turns the Semtech LR2021 LoRa transceiver into a software-defined radio (SDR). On 27 October 2026 the author relicensed it under the MIT licence. The same day he merged firmware changes for transmitting at up to 1 million samples per second. CNX Software first described the project on 20 October, when the library was still under GPL-3.0.
What the project does
Normally the LR2021 demodulates LoRa, FSK, FLRC and other signals itself and hands only finished packets to the host processor. The project uses an undocumented command in the chip's ROM to expose the raw baseband signal as 16-bit I/Q samples. Software on the host can then decode signals the chip's packet engine does not support. Examples include P25 Phase 1 digital voice, POCSAG pager messages and analogue FM. The chip's own Bluetooth LE engine also receives advertising packets on all three advertising channels.
The tested receive range is 100 MHz to 2.74 GHz, well beyond the datasheet's 150-960 MHz and 1.5-2.5 GHz. The README now lists sustained reception over Wi-Fi at 500,000 samples per second with 16-bit samples and up to 800,000 with 8-bit samples, with every sample delivered to the computer. On the computer side the board appears as an ordinary SoapySDR device (driver=lr2021), so GNU Radio, SDR++ and other SoapySDR programs can use it on Linux and macOS.
Hardware
The tested platform is the LilyGO T-Display P4 with an LR2021 running ROM 1.24. The ESP32-P4 drives the radio over SPI. The SX1262 variant of the same board uses a different chip and does not work. The author's other project, LakeShark, turns the T-Display P4 into a handheld scanner. With LR2021-SDR it can decode P25 voice, pagers and FM without an external RTL-SDR dongle. A standalone ESP32-P4 firmware captures samples over USB for analysis on a computer.
All measurements come from one board. The README warns that the range depends on the module's front end and may differ on other boards.
Transmitting, carefully
The project can also transmit short bursts. These include P25 test signals, custom waveforms and replayed remote-control signals, which independent receivers have confirmed. CNX Software reports tests in which rtl_433 received temperature sensor data and a Flipper Zero decoded replayed remote signals. Transmit support is still experimental, and continuous transmission and live voice were not finished at the time of the CNX report.
The receive side is a useful tool for anyone studying 433 and 868 MHz home sensors or checking what their devices broadcast. The transmit side carries legal risk. Transmitting outside the bands and power limits allowed in a given country, or replaying other people's remote-control signals, can be illegal. That responsibility lies with the user, not the project.
Licence change
The relicensing commit says the MIT licence "suits a driver: anyone can use it, build on it and ship it" as long as the copyright notice is kept. Releases made before that commit remain available under GPL-3.0. An AI_USE.md file adds that ports, translations and AI-regenerated versions of the code also count as copies and must keep the notice. The project calls itself experimental.