(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example demonstrates how to use IIR filters functionality from esp-dsp library. Example does the following steps:
- Initialize the library
- Initialize input signal
- Show LPF filter with Q factor 1
- Calculate iir filter coefficients
- Filter the input test signal (delta function)
- Shows impulse response on the plot
- Shows frequency response on the plot
- Calculate execution performance
- The same for LPF filter with Q factor 10
This example does not require any special hardware, and can be run on any common development board.
If using Make based build system, run make menuconfig and set serial port under Serial Flasher Options.
If using CMake based build system, no configuration is required.
Also, under Component Config/DSP Library/Optimization for ESP32, it's possible to select optimized or ansi implementation to compare.
Build the project and flash it to the board, then run monitor tool to view serial output:
make -j4 flash monitor
Or, for CMake based build system (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.
Here is an typical example console output.
I (58) main: Start Example.
I (58) main: Impulse response of IIR filter with F=0.100000, qFactor=1.000000
I (68) view: Data min[8] = -0.060052, Data max[2] = 0.333517
________________________________________________________________
0 |
1 |
2 - |
3- - |
4 -------------------------------------------------------------|
5 |
6 |
7 |
8 |
9 |
0123456789012345678901234567890123456789012345678901234567890123
I (138) view: Plot: Length=128, min=-1.000000, max=1.000000
I (148) view: Data min[511] = -149.983795, Data max[0] = 0.000000
________________________________________________________________
0 |
1 |
2----------------- |
3 ---------- |
4 ------------- |
5 ---------- |
6 ------- |
7 --- |
8 -- |
9 --|
0123456789012345678901234567890123456789012345678901234567890123
I (228) view: Plot: Length=512, min=-100.000000, max=0.000000
I (228) main: IIR for 1024 samples take 20276 cycles
I (238) main: Impulse response of IIR filter with F=0.100000, qFactor=10.000000
I (248) view: Data min[7] = -0.453739, Data max[2] = 0.526114
________________________________________________________________
0 |
1 |
2 - - |
3- - - - --- --- - - |
4- - - - - ---- -------------------------------------|
5 -- -- -- -- |
6 |
7 |
8 |
9 |
0123456789012345678901234567890123456789012345678901234567890123
I (318) view: Plot: Length=128, min=-1.000000, max=1.000000
I (328) view: Data min[511] = -149.480377, Data max[0] = 0.000000
________________________________________________________________
0 -- |
1 -- - |
2---------- ----- |
3 -------- |
4 ------------ |
5 ---------- |
6 ------- |
7 --- |
8 -- |
9 --|
0123456789012345678901234567890123456789012345678901234567890123
I (408) view: Plot: Length=512, min=-100.000000, max=0.000000
I (408) main: IIR for 1024 samples take 17456 cycles
I (418) main: End Example.