A developer who posts as SAMS0N1TE has released LR2021-SDR. The repository describes it as an "Experimental LR2021 raw I/Q capture library and tools in C". It reads raw 16-bit I/Q samples from Semtech's LR2021 LoRa transceiver over SPI, which lets the chip work as a basic software-defined radio. CNX Software names the creator as Samuel Reynolds. The code is published under GPL-3.0 and is marked experimental.
Hackaday wrote about the find on October 15, 2026, and CNX Software followed on October 20, five days later. In Hackaday's article, Jenny List credits [Samson1te], who posted the project in a comment on an earlier Hackaday post.
What the project does
The raw I/Q access relies on an undocumented command in the LR2021's ROM. With it, the chip streams its baseband samples to a host microcontroller. The repository contains a C library, capture firmware and a set of tools. CNX notes that it also includes standalone ESP32-P4 capture firmware that sends I/Q samples over USB to a computer for analysis.
Testing used a single LilyGO T-Display-P4 LR2021 board, on which an ESP32-P4 runs the receivers. The chip ran LR2021 ROM 1.24. LakeShark firmware runs on the same handheld. CNX points out that LakeShark otherwise turns the T-Display-P4 into an SDR scanner by using an external RTL-SDR dongle.
The repository reports these results:
- Receive range: continuous receive from 100 MHz to 2740 MHz (experimentally tested). That goes beyond the LR2021 datasheet bands of 150–960 MHz and 1.5–2.5 GHz. Below 100 MHz, image calibration fails. Above about 2750 MHz, the synthesizer does not lock. Range depends on the module's front end and may differ on other boards.
- Sample rate: clean captures at up to 250,000 complex samples/s. At 125,000 samples/s, three streaming sessions ran for up to 391 seconds with no reported FIFO loss.
- Bottleneck: the SPI bus tops out at 16 MHz, and the CPU reads the FIFO. At 500,000 and 1,000,000 samples/s the FIFO overflowed. The repository says a faster read path could change this.
- Decoding: live P25 Phase 1 voice, POCSAG pagers and analog FM in LakeShark. The chip's own BLE engine picks up advertising on all three channels. 2-FSK at 2400 baud was decoded offline from saved captures, with CRC-16 checks.
- Transmit: custom waveforms, P25 test bursts, temperature packets, and OOK/FSK replay at 915 MHz and 433.92 MHz. Transmission is limited to short bursts, and the transmit path is experimental.
The author reports two transmit checks. An independent receiver recovered 72 P25 voice frames from one transmission, and a Flipper Zero decoded Princeton remote keys replayed by the LR2021. The repository also lists clear caveats: all results come from one board, amplitude is uncalibrated, and signal levels are relative. The frequency range and sample rates are one developer's bench results, not a specification.
Where it fits
Hackaday's headline calls this "another" wireless chip with a hidden SDR. It links the find to the ESP32, which was turned into an SDR through a hidden baseband mode. In the comments, Jenny List writes that "Someone in the know suggested to me that these hidden functionalities are there for testing purposes," as part of manufacturing QA. Another commenter points out that some chips, such as the STM32WL33, have a documented IQ interface.
The repository credits ESP-SDR and the ESPARGOS team as inspiration. It also says that no ESP-SDR code is included.
What It Means for Makers
LR2021-SDR is for radio experimenters and firmware developers who already have an LR2021 board and want to explore what the chip can capture. Hackaday says "it's early days", and adds that "Currently the main demo is P25 digital voice."
Compatibility is narrow. Everything has been tested on one board, and results may differ on other LR2021 modules. CNX says the firmware is "not compatible with the SX1262 variant for raw I/Q access", so owners of SX1262 boards should not expect the same results. The C library, capture firmware and tools are in the GitHub repository, which also tracks the project's status.
Receive-only experiments are the low-risk way to start. The transmit features send signals on real frequencies, including P25 bursts and replayed remote-control codes. Check your local radio regulations and the repository's documentation before you enable them.
