IIR Filters - Theory and Implementation (STM32) - Phil's Lab #32

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Tutorial on IIR (Infinite Impulse Response) digital filters, including digital filtering overview, IIR filter theory, FIR vs IIR, Z-transform design/analysis, design using analogue prototypes, and finally an implementation on an embedded system (STM32).
Free trial of Altium Designer: www.altium.com/yt/philslab
Visit jlcpcb.com/RHS for $2 for five 2-layer PCBs and $5 for five 4-layer PCBs.
Patreon: / phils94
Git: github.com/pms67
[TIMESTAMPS]
00:00 Introduction
00:19 JLCPCB and LittleBrain Files
00:54 Altium Designer Free Trial
01:26 Content
01:44 Digital Filter Basics
04:13 FIR vs IIR
05:41 IIR Filter Theory
10:15 IIR Filter Design Example 1 (Z-Transform)
13:54 IIR Filter Design Example 2 (Analogue Prototype)
15:41 Implementation (Header and Source Files)
17:47 Implementation (main.c)
18:48 Demonstration
ID: QIBvbJtYjWuHiTG0uCoK

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13 июл 2024

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Комментарии : 89

@Jose-tw9bl 2 года назад

In just under 20 minutes you've designed the filter, showing the theory, code, and results. You are the best! thanks!

@muniswamy100 Месяц назад

How I Wish, How I wish, you were there(during my university days) I was like a lost soul swimming in a books bowl, year after year(took 2 years to clear my DSP paper) Running over this RU-vid ground, what have I found, Wish you were there!

@Stefek994 2 года назад

I am amazed how well you explained it. I studied this in university and still enjoy watching.

@ninefox344 2 года назад

Seconded, very nice refresher.

@dancollins1012 2 года назад

Truly exceptional content! Clear, focussed, detailed. Thank you, thank you

@PhilsLab 2 года назад

Thank you so much, Dan!

@brctoms2203 2 года назад

Please do a video on implementation of kalman filters You really know how to teach...!!!

@kamil13877 2 года назад

I'm looking forward to watch your course. There is so much to learn from you. Keep up the good work!

@trollgarten Год назад

First class exceptional content! I had this topic ages ago during my studies, but never applied it to real world (at least not by myself), but now facing problems with big data & noise (you have always noise in the data) you video series is a great tool box to tackle my problems and have fun as well!

@EhsanAlnazi 2 года назад

I really like all your videos that process and reducing the noise.

@kenwallace6493 2 года назад

Once again Phil shows a clear, consistent process that we self-taught programmers can only dream of. We get the same result (usually) but not nearly as elegant.

@Philip8888888 2 года назад

Great video and great teaching style. Thanks!

@sayantanmaiti2513 2 года назад

This is really an excellent explanation like that of ur previous filter videos. I have used Tustin method to make it better. Now I can directly attach my PPG analog data into 12 bit ADC of ESP32 and filter out digitally

@kindaFunkyNGL 2 года назад

After 5 years of schooling, I have now learned what a bodie plot is in 15 seconds! Thankyou

@supremeleader5516 8 месяцев назад

I am currently leaning DSP in college, our professor teach it like maths, and make it boring. after watching your video, i realised the power of DSP and i generated my interest in this field. thanks Phil.

@gretarmark 2 года назад

What a great explanation!

@helgeb5403 2 года назад

Really nice work! ... as always. I love your channel.

@PhilsLab 2 года назад

Thank you, Helge!

@_a_x_s_ 2 года назад

Wow, just released 15 seconds ago. Finally, IIR filter. Good work!

@PhilsLab 2 года назад

Thank you!

@soufiane_krem 2 года назад

Great Explanation of this concept .Thanks!

@PhilsLab 2 года назад

Thanks for watching!

@shakaibsafvi97 2 года назад

Wow ! Amazing work....

@cyberphox1 2 года назад

Great tutorial!

@osamadz5884 2 года назад

Good work ,Waiting for the next video

@horizon586 Год назад

really good explaination!!

@PhilsLab Год назад

Thanks!

@djredrover Год назад

Wow, Thank you. I have been struggling with these actuator spikes for my TVC hovercraft vehicle, which were a result of a mistake in the code of my filter functions. I had confused the formula for a complementary filter and an IIR filter which was giving me wild results. Thank you Thank you Thank you!

@hoytvolker3 Год назад

Very informative keep it up

@user-om7os8gj8x Год назад

Thank you !

@mmk34 2 года назад

Love it great video.

@dixon1e 2 года назад

Yes! Thank you Phil!!!

@PhilsLab 2 года назад

Thank you for watching, Dixon!

@yamanseyravan2341 2 года назад

Your videos helped me get a really good job after I graduated they are really helpful, Keep the good work! :D

@PhilsLab 2 года назад

Very glad to hear that, thank you, Yaman!

@ajoyraman1409 Год назад

Great job! Thanks

@PhilsLab Год назад

Thanks!

@MinisterstvoMekhatroniky Год назад

Thank you for your video!

@PhilsLab Год назад

Thanks for watching!

@kendydrechsler4956 2 года назад

THIS is so impressive! Could you also make a video about how to model non linearities like diodes, tubes and stuff like that? Such realy understandable videos like yours are so rare on RU-vid! Thanks you so much, your work is so inspiring!

@Bianchi77 2 года назад

Nice video, thanks :)

@timovandrey Год назад

Unbelievably good!

@PhilsLab Год назад

Thank you, TImo!

@Prestige1d 2 года назад

Thank you

@MrRonychakraborty 2 года назад

Nice tutorial as always. Dear Phil Can u please make tutorial on madgwick filter and extended kalman filter for sensor fusion.

@whimsicalvibes6233 2 года назад

Thanks a lot

@rolfw2336 2 года назад

BTW, I'm pretty sure that the "general form" equation at 6:14 should have a term "y[n - j]" instead of "y[n - B]" in the 2nd summation. Otherwise, great video, Phil.

@arzamas1988 2 года назад

Thx!

@7177YT 2 года назад

Brillant! Thank you! Subscribed! ((:

@PhilsLab 2 года назад

Thank you very much!

@robdavis3220 2 года назад

Great video's. Would love to see how to implement a higher order ( say 2 or3 ) filters.

@jrioublanc 2 года назад

Thanks

@PhilsLab 2 года назад

Thanks for watching!

@charlesgalant8271 2 года назад

Huh, I've been doing a "weighted moving average" like this for ages to smooth out data, didn't realize it had a proper name. Would be very interested to see what a higher order version looks like, I'd never considered doing that (as-is this barely warrants the struct). Are alpha and beta always linked like this?

@sayantanmaiti2513 2 года назад

Weighted moving average is an FIR filter. Since it only dependent on present and previous inputs. It doesn't depend on previous outputs. Therefore it is a non recursive filter, that is, FIR. As per analog devices, it has a good simple filtering property in time domain but ghastly frequency domain response

@ytubeleo 2 года назад

People often confuse the names moving average (probably the simplest FIR filter) with running average (probably the simplest IIR filter).

@suncrafterspielt9479 2 года назад

Finally iir

@anjayv8347 2 года назад

Phil Awesome video on IIR filters. What do you think about median filters on embedded systems ?

@TDMLab 2 года назад

Cool!

@PhilsLab 2 года назад

Thanks!

@rolfw2336 2 года назад

These videos are great! I really like the theory "warm up" at the beginning. By the way, just wondering how you do the "blackboard" for text and formulas, namely what tool you use for that? Cheers, -Rolf

@PhilsLab 2 года назад

Thanks, Rolf - very glad to hear that. I use Notability on my iPad for the 'blackboard' stuff.

@KillzoneKid 2 года назад

Thanks for the video, it prompted me to look further and I found discrepancy between your formula of first order IIR filter and common formula. It seems the coefficients are swapped around in your example. Is this intentional? Of course with alpha at 0.5 it won’t make any difference to the output result

@yashodhanvivek8086 2 года назад

Phil ,are you selling these boards that you have designed and shown in the video. I will be interested in buying the one

@shaungovender7805 2 года назад

Hi Phil... Great content as always, I do have one question though... The STM32 MCU has specialized DSP libraries written by ARM (I think). Is there a reason why you do not use this library or do you write your code from "first principles" for a better explanation process? Also a suggestion for a future video is to show the design process of a IIR filter which would meet specific design requirements such as a cut-off frequency. Then sample an input waveform below the cut-off and show it is unaffected by the filter. Then sample an input of higher frequency than the cut-off and show the attenuation.

@jamescuttsmusicjcm5013 Год назад

yesss

@MrRobertSJC 2 года назад

Hi Phil, Can you give a pointer on how to implement a LC filter?

@mostafakh5075 2 года назад

hey phil, i have implemented iir filter for magnetometer, it smooth the data but then it's not real time, it makes a little delay to update for yaw axes, do have any suggestions to solve it? i

@mrechbreger 2 года назад

Not sure how you sample the data in since I did not see the sensor video, if it's analog is there no (on-chip) filter available which can be applied during sampling the data? I'm using an (onchip) IIR filter when sampling audio via ADC with another chipset.

@t7732155980 2 года назад

You are correct but this is done on purpose. The way the signal is acquired is not important for understanding the filter design and operation. For example, you could get ADXL355 IMU (see Phil's video from Aug 21th 2021) via i2c or from a barometric pressure sensor (Phil's Apr 14, 2021) via SPI. The important this is to understand that once you have evenly spaced sample of the signals (the x values in this video) you can apply a digital filter to those samples.

@noelj62 2 года назад

Good and clear presentation. Though the writing on a black background is not easy on the eyes especially on a mobile device. Not to mention sudden transitions between bright and black screens which is also distracting. Thank you and good continuation.

@nova0302 Год назад

Hello Bro! I appreicate all you fantastic works on youtube. Would that be possible for yot to shed some light on pdm2pcm conversino of mems microphone data?

@merveozdas1193 Год назад

Hi, your video is amazing, but I couldn't understand your inference at 15.03 minutes (T/T+RC)*Vin[n]+ (RC/T+RC)*Vout[n-1] how did you infer this? I couldn't understand exactly, thank you :)

@JohnJTraston 2 года назад

I can't read anything on those slides. Why? Can you just type it in normal font?

@sukhoy 2 года назад

A first order filter like this is basically a weighted moving average of just 2 values.

@sourabhmestry9933 2 года назад

Thanks, Great explanation as always. Is full PCB design course available?

@rjordans 2 года назад

Nice one! Maybe as a follow-up, can you show how to do this with MCUs that don't have floating point support? How to get proper scaling for doing this with just integer arithmetic and what impact the resulting rounding has on the filter design.

@patrickhochleitner7754 2 года назад

As always a superp exposition. I do however have some questions. In the FIR filter you also used the low pass first order filter. Does this means it can be used for both? Also, if I understand correcly IIR are better served at RT applications? What else? Thanks again!

@shaungovender7805 2 года назад

The IIR and FIR filters can be designed to be low-pass, high-pass or band-pass. The functionality of filter is determined by the design process... The difference between IIR and FIR is the actual make up of the filter. FIR filter computes it's current output by only using the input. IIR filters computes its current output by using the input and the previous outputs. To make an analogy to continuous-time filters, FIR is a passive filter and IIR is an active filter (it has output feedback)

@MinhTran-wn1ri 2 года назад

Why do we prefer smooth signals in the first place?

@ytubeleo 2 года назад

Usually to remove high-frequency noise (useless information), or to remove high-frequency components before sampling to prevent aliasing. For example, if I sample a sensor at 10 Hz, I must make sure there is no significant components above 5 Hz, otherwise they will be "reflected" off that limit and cause aliasing. Also, in this example, a low-pass filter was made but you can also make high-pass to remove a DC component or a notch filter to remove 50 Hz powerline interference.

@anunez20 2 года назад

The theory and application related to digital filters is not easy. I'm revising the book "Discrete-time signal processing" of Oppenheim and Shafer and it is heavy ...