4.3 KiB
FFT 4 Real Input Example
(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example demonstrates how to use FFT functionality from esp-dsp library. Example does the following steps:
- Initialize the library
- Initialize input signals with 1024 samples: one 0 dB, second with -20 dB
- Calculate FFT Radix-2 for 1024 complex samples
- Calculate FFT Radix-4 for 1024 complex samples
- Apply bit reverse operation for output complex vectors
- Show results on the plots
- Show execution time of FFTs
How to use example
Hardware required
This example does not require any special hardware, and can be run on any common development board.
Configure the project
Under Component Config ---> DSP Library ---> DSP Optimization, it's possible to choose either the optimized or ANSI implementation, to compare them.
Build and flash
Build the project and flash it to the board, then run monitor tool to view serial output (replace PORT with serial port name):
idf.py -p PORT flash monitor
(To exit the serial monitor, type Ctrl-].)
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
Example output
Here is an typical example console output.
I (344) main: Start Example.
W (424) main: Signal x1
I (424) view: Data min[673] = -103.113297, Data max[328] = 20.490950
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0123456789012345678901234567890123456789012345678901234567890123
I (494) view: Plot: Length=1024, min=-60.000000, max=40.000000
W (504) main: Signal x2
I (504) view: Data min[582] = -103.113297, Data max[328] = 20.490950
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0123456789012345678901234567890123456789012345678901234567890123
I (584) view: Plot: Length=1024, min=-60.000000, max=40.000000
W (593) main: Difference between signals x1 and x2 on one plot
I (594) view: Data min[0] = 0.000000, Data max[392] = 0.313019
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8----------------------------------------------------------------|
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0123456789012345678901234567890123456789012345678901234567890123
I (674) view: Plot: Length=1024, min=0.000000, max=40.000000
I (674) main: FFT Radix 2 for 1024 complex points take 168652 cycles
I (684) main: FFT Radix 4 for 1024 complex points take 104665 cycles
I (694) main: End Example.