# IIR Filter Example (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: 1. Initialize the library 2. Initialize input signal 3. 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 4. The same for LPF filter with Q factor 10 ## 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 (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. ```
To create a project from this example, run:
idf.py create-project-from-example "espressif/esp-dsp=1.4.8:iir"