The PhaseLatch Mini is a low-cost software-defined radio digitizer built around the STM32F103C8 Arm Cortex-M3 microcontroller in a compact Blue Pill-style form factor. Designed as a companion to the previously released Phase Loom tuner, the board targets HF, FM, and VHF experimentation with dual simultaneous 12-bit ADCs that capture I and Q signals at 210,500 sample pairs per second, streaming over USB-C at roughly 500 KiB/s using the standard CDC interface.
The 60.2 mm x 20.8 mm (2.4 in x 0.8 in) four-layer board features two SMA edge connectors with an onboard passive 100 kHz low-pass filter network per channel, built from multi-stage LC components including 10 µH inductors and shunt capacitors. Power filtering includes ferrite beads and decoupling throughout the analog path, while dedicated 8 MHz and 32.768 kHz crystals provide stable timing. The firmware uses circular DMA with half and full callbacks, ISR-driven packet chaining, and a lock-free USB feed path to maintain high-rate streaming without dropped samples.
Python-based host utilities on GitHub handle live monitoring, raw I/Q capture, GQRX and GNU Radio integration, and throughput diagnostics. Tools like host_test.py, host_iq_live.py, and host_iq_fifo.py support continuous streaming, real-time visualization, FIFO bridging, and bulk-data capture with drop-resilient handling. The firmware exposes ASCII control commands (START, STOP, A, F) over USB-CDC while host scripts decode ADC and DMA counters, track packet efficiency, and measure effective sample rate.
Compared to wideband transceivers like the HackRF Pro (100 kHz to 6 GHz, 20 MSPS 8-bit I/Q) or dongle-grade receivers like the RTL-SDR Blog V4 (8-bit RTL2832U), the PhaseLatch Mini trades frequency range and speed for cleaner synchronized 12-bit dual-ADC capture, proper analog filtering, and reliable mid-speed USB streaming. This positions it above basic dongles in signal quality and I/Q fidelity while remaining simpler and more affordable than full-featured SDR platforms.
The PhaseLatch Mini is available for 199 DKK ($31, €28). The Phase Loom tuner board sells separately for 300 DKK ($46, €42).