Introduction

The Software Frequency Response Analyzer (SFRA) is a software library that enables developers to quickly measure the frequency response of their digital power converter. The SFRA library contains software functions that inject a frequency into the control loop and measure the response of the system using the Sitara MCUs’ on-chip analog to digital converter (ADC). This process provides the plant frequency response characteristics, the open loop gain frequency response and the closed loop frequency response of the closed loop system.

This library contains header file (sfra_f32.h) and ".lib" file based on release/debug configuration.

Features Supported

SFRA module includes calculation and storage of following:

User configurable sweep start frequency, frequency step size, injection amplitude
Plant Magnitude and Phase vector corresponding to frequency points configured by user
Open loop Magnitude and Phase vector corresponding to frequency points configured by user
Closed loop Magnitude and Phase vector corresponding to frequency points configured by user

SFRA contains Matlab scripts used for following:

Extract the data from excel sheet (which needs to be in same format as "SFRA.xlsx") and plot the boded plots
Compare boded plots with laplace transfer function provided in script (user can change transfer function as per use case)
Script uses sisotool to design the compensation based on boded plots (User need access for Matlab Control System Toolbox)

Features Not Supported

GUI is not supported

Benchmark Results

A benchmark on R5F core has been conducted to observe the following results when running the following functions:

SFRA Function	Cpu Cycles
SFRA_F32_reset	15
SFRA_F32_config	15
SFRA_F32_inject	66
SFRA_F32_collect	37
SFRA_F32_runBackgroundTask	89

SFRA Obj files	Code Size(Bytes/8bits)
SFRA_F32_reset + SFRA_F32_config	424
SFRA_F32_inject + SFRA_F32_collect + SFRA_F32_runBackgroundTask	1522

Ran with TI Clang Compiler v3.2.1.LTS, with -Os flag and functions force-inlined onto the benchmarking function placed in TCM memory. Obtained the average result from 500 consecutive loops of running sfra functions with DPL CycleCountP, mimicking the usage of a control loop and overhead (~10 cycles) is removed.
Actual result may vary depending on provided datasets and memory configuration. For R5F, it is recommended for users to map control loops to TCM for the best performance.

Provided Examples

The following examples has been provided to demonstrate sfra module:

Software frequency response analyzer Test

Additional References

N/A

API

APIs for Software Frequency Response Analyzer Library

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