Two independent SDR drivers for the MediaTek MT7921AU Wi-Fi chipset appeared within days of each other, part of a broader wave of undocumented I/Q sampling features being uncovered across wireless chips since an ESP32 discovery two weeks ago.
BirriaSDR uses libusb to stream raw I/Q samples at 40 Msps in 14-bit resolution, tunable from 2156 to 2610 MHz, with no permanent firmware changes and an RTL-SDR-compatible API. Mtk79ICAP takes a different path: it requires modified firmware and a custom driver, but delivers up to 80 MHz bandwidth, reaches 5 GHz bands, and exposes the chip through a standard SoapySDR interface. Mtk79ICAP can also run simultaneously in Wi-Fi monitor mode while streaming SDR data, provided automatic gain control is active.
This is the second MediaTek chip repurposed this way, following the MT7996. The piece is worth reading in full for the technical contrast between the two driver approaches, and because the trajectory here is clear: external antennas on these adapters make frequency mixer integration straightforward, and ESP32-based variants are already transmitting arbitrary signals.
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