A developer called shraiwi implemented the FAST corner detection algorithm on an ESP32-S3 using its SIMD instruction set, achieving real-time VGA video processing at 30 FPS on a 240 MHz microcontroller. The result is a 2x speedup over a naive, non-SIMD implementation. The full project and PlatformIO source code are on GitHub.
The FAST algorithm, Features from Accelerated Segment Test, identifies corners in image frames, a core primitive for machine vision pipelines. Getting it onto the ESP32-S3's Xtensa LX7 SIMD ISA required direct assembly work, and the ISA fought back: no unsigned byte comparisons, no misaligned read support. Shraiwi solved both with workarounds worth reading in detail.
The real value here is not the benchmark number. It is the annotated walkthrough of working within a constrained SIMD ISA on a $5 microcontroller, writing assembly to compensate for missing instructions. Anyone targeting embedded vision or exploring the ESP32-S3's twin-core LX7 architecture will find the technical decisions documented here directly applicable.
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