Dynamic Precision Math Engine for Linear Algebra and Trigonometry Acceleration on Xtensa LX6 Microcontrollers

TL;DR

This paper introduces a dynamic precision math engine for ESP32 microcontrollers that enhances the performance of linear algebra and trigonometry computations by switching between fixed-point and floating-point arithmetic at runtime.

Contribution

It presents a novel architecture combining fixed-point, CORDIC, and tiled matrix multiplication with runtime precision switching for embedded processors.

Findings

CORDIC module achieves median latencies of 293 cycles for sine and cosine

Speedups of 18.5x for sine and 24.7x for cosine over standard math library

Significant performance improvements for numerical computations on low-cost microcontrollers

Abstract

Low-cost embedded processors such as the ESP32 (Xtensa LX6, 32-bit dual-core, 240 MHz) are increasingly used in edge computing applications that require real-time physical simulation, sensor fusion, and control systems. Although the ESP32 integrates a single-precision IEEE 754 floating-point unit, floating-point operations introduce pipeline overhead and higher energy consumption compared to integer arithmetic, limiting throughput for floating-point intensive workloads. This paper presents the design, formal specification, and empirical evaluation of a Dynamic Precision Math Engine for the ESP32. The system integrates three main components: a Q16.16 fixed-point arithmetic core that maps mathematical operations onto the integer pipeline of the Xtensa LX6, a 16-iteration CORDIC trigonometric module that computes sine and cosine using only additions and bit shifts, and a cache-aware tiled matrix multiplication kernel with deferred correction to reduce rounding operations. The architecture introduces a runtime precision switching mechanism implemented through function pointer dispatch and a synchronization protocol compatible with FreeRTOS. This mechanism allows applications to dynamically transition between a fast fixed-point execution path and a precise IEEE 754 floating-point path without recompilation. Experimental evaluation on ESP32-WROOM-32 hardware using 300 paired measurements shows that the CORDIC trigonometric module achieves median latencies of 293 cycles for both sine and cosine, corresponding to mean speedups of 18.5x and 24.7x compared to the standard math library. The results demonstrate that precision-aware software architecture can significantly improve numerical performance on low-cost microcontrollers.