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FFT Module API Manual

Overview

The FFT (Fast Fourier Transform) module is used to perform Fourier transform on input time-domain data, converting it into frequency-domain data and returning the corresponding frequency amplitudes. Through FFT computation, time-domain signals can be effectively converted into frequency-domain signals, facilitating the analysis of signal frequency components.

API Introduction

The FFT module provides an FFT class that supports three main functions: run(), freq(), and amplitude(), used for fast Fourier transform, frequency calculation, and amplitude calculation respectively.

Class machine.FFT

Description

This class is used to create FFT objects and perform Fourier transform on input data.

Syntax

from machine import FFT
import array

# Define time-domain data
data = array.array('i', [1, 2, 3, 4, 5, 6, 7, 8])

# Create an FFT object, perform 64-point FFT computation, offset is 0
fft1 = FFT(data, 64, 0)

Parameters

Parameter Name	Description	Type	Input/Output
data	Input time-domain data, bytearray type.		Input
points	Number of points for FFT computation, supports 64, 128, 256, 512, 1024, 2048, and 4096 points.		Input
shift	Data offset, default is 0.		Input

Return Value

Return Value	Description
0	Operation successful.
Non-0	Operation failed.

run() Method

Description

This function is used to obtain the frequency-domain data after Fourier transform.

Syntax

res = FFT.run()

Parameters

None

Return Value

Return Value	Description
res	Returns a list containing frequency-domain data, which contains points tuples, each containing 2 elements: real part and imaginary part.

freq() Method

Description

This function is used to obtain the calculated frequency values.

Syntax

res = FFT.freq(points, sample_rate)

Parameters

Parameter Name	Description	Input/Output
points	Number of points participating in FFT computation.	Input
sample_rate	Data sampling rate.	Input

Return Value

Return Value	Description
res	Returns a list containing the frequency values of each frequency point after computation.

amplitude() Method

Description

This function is used to calculate the amplitude of each frequency point, mainly for testing purposes. Users can write more complex amplitude processing functions in Python on their own.

Syntax

amp = FFT.amplitude(FFT_res)

Parameters

Parameter Name	Description	Input/Output
FFT_res	FFT computation result returned by the run() function.	Input

Return Value

Return Value	Description
amp	Returns a list containing the amplitudes of each frequency point.