92 lines
4.3 KiB
Markdown
92 lines
4.3 KiB
Markdown
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# FFT Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example demonstrates how to use FFT functionality from esp-dsp library. Example does the following steps:
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1. Initialize the library
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2. Initialize input signals with 1024 samples: one 0 dB, second with -20 dB
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3. Combine two signals as one complex input signal and apply window to input signals paar.
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4. Calculate FFT for 1024 complex samples
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5. Apply bit reverse operation for output complex vector
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6. Split one complex FFT output spectrum to two real signal spectrums
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7. Show results on the plots
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8. Show execution time of FFT
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## How to use example
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### Hardware required
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This example does not require any special hardware, and can be run on any common development board.
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### Configure the project
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Under Component Config ---> DSP Library ---> DSP Optimization, it's possible to choose either the optimized or ANSI implementation, to compare them.
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### Build and flash
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Build the project and flash it to the board, then run monitor tool to view serial output (replace PORT with serial port name):
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```
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idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example output
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Here is an typical example console output.
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```
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I (59) main: Start Example.
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W (89) main: Signal x1
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I (89) view: Data min[495] = -162.760925, Data max[164] = 23.938747
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________________________________________________________________
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0123456789012345678901234567890123456789012345678901234567890123
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I (159) view: Plot: Length=512, min=-60.000000, max=40.000000
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W (169) main: Signal x2
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I (169) view: Data min[502] = -164.545135, Data max[205] = 3.857752
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________________________________________________________________
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0123456789012345678901234567890123456789012345678901234567890123
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I (249) view: Plot: Length=512, min=-60.000000, max=40.000000
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W (249) main: Signals x1 and x2 on one plot
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I (259) view: Data min[505] = -159.215271, Data max[164] = 23.938747
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________________________________________________________________
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0123456789012345678901234567890123456789012345678901234567890123
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I (339) view: Plot: Length=512, min=-60.000000, max=40.000000
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I (339) main: FFT for 1024 complex points take 140472 cycles
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I (349) main: End Example.
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```
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