LR2021 SDR: Turning a LoRa Chip Into a Software Radio

Hidden software-defined radios are having a moment. After hackers recently found SDR modes inside the ESP32 and a Wi-Fi 7 router, a new open-source project called LR2021-SDR does the same for Semtech's LR2021 LoRa transceiver. Hackaday first highlighted the work on October 15, 2026, and CNX Software published a detailed breakdown on October 20. The developer, Samuel Reynolds (SAMS0N1TE on GitHub), uses an undocumented command in the chip's ROM to expose raw 16-bit I/Q samples, turning a low-cost IoT radio into an experimental receiver from 100 MHz to 2.74 GHz.

• Hardware: Semtech LR2021 running ROM 1.24; the SX1262 does not support the raw I/Q trick
• Tested range: reception and short transmit bursts from 100 MHz to 2.74 GHz on one test board, beyond the datasheet's 150 to 960 MHz and 1.5 to 2.5 GHz bands
• Sample rates: clean short captures at up to 250,000 complex samples per second, and continuous capture at 125,000 samples per second for up to 391 seconds
• License: GPL-3.0 C library, standalone ESP32-P4 capture firmware and Python tools on GitHub

What Is the LR2021-SDR Project?

Normally, a LoRa chip like the LR2021 does its signal processing internally and hands the host processor finished packets of LoRa, FSK or similar data. A software-defined radio instead passes along the raw baseband signal, as I and Q samples, so software can decode whatever it wants. As Hackaday notes, many modern radio chips use SDR techniques inside but never expose them; such hidden modes are often there for factory testing.

LR2021-SDR taps that hidden path. According to CNX Software, the library reads 16-bit I and Q samples over SPI, which software can then demodulate. The developer pairs it with LakeShark, their own open-source firmware that already turns the LilyGO T-Display P4 into a handheld scanner. With LR2021-SDR, LakeShark can receive analog FM and other signals without an external RTL-SDR dongle.

How Far Can a LoRa Chip Go as an SDR?

CNX Software reports that the developer confirmed reception at 100 MHz, 1.3 GHz, 2.6 GHz and 2.74 GHz using clock harmonics and test signals from a HackRF One inside a shielded enclosure. The chip's built-in BLE engine can also receive Bluetooth LE 1M advertising packets on channels 37, 38 and 39. Raw recordings support offline analysis and replay, including triggered captures that keep pre-trigger samples.

The main bottleneck is the 16 MHz SPI link. Short captures at 250,000 samples per second worked, but 500,000 and 1,000,000 samples per second overflowed the chip's FIFO because the interface could not move data fast enough. Transmit support is experimental and limited to short bursts; in testing it sent sensor-style data that the rtl_433 tool decoded. The developer is clear that results come from a single board and do not establish calibrated sensitivity.

What Can Makers Build With It?

This is a learning project first, and a brilliant one. Students and hobbyists can study modulation, capture real signals for offline decoding, or build a pocket scanner from hardware they may already own. Anyone experimenting should check local rules on which bands may be received and transmitted, and keep transmit tests to licensed or low-power use. If you want to understand where LoRa fits among mesh radio options, our Meshtastic vs MeshCore vs LoRaWAN guide is a good primer, and the ESP32 SDR firmware story shows the same idea on a different chip. More maker hardware lives in our mini computers coverage.

Sources: CNX Software — October 20, 2026; Hackaday — October 15, 2026; LR2021-SDR on GitHub — October 2026.