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Forum Index : Microcontroller and PC projects : [MicoMite] Sound issue
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fmafma Newbie  Joined: 30/06/2023 Location: FrancePosts: 31 |
Hi! I added sounds to my 1D-pong-like game, and I have a strange behaviour: there is a bad 'clac' at the end of each sound played. Any idea what can cause that? Note they are ok when played alone from command line... The code is visible here. Thanks, Frédéric Frédéric |
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Martin H. Guru  Joined: 04/06/2022 Location: GermanyPosts: 1113 |
You use CONST SND_START = "start.wav" CONST SND_BUMP = "bump.wav" CONST SND_LOOSE = "loose.wav" CONST SND_WIN = "win.wav" and PLAY WAV to play them .. that is fine, so far but we dont know, how does the wav Files look ... Maybe you can use an Audio Editor and "fade out" the end of the Waves so that they all end on 0 Edited 2023-09-29 18:52 by Martin H. 'no comment |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
The files are ok, I checked with Audacity. The final 'plop' occurs after the end of the files, but only when played from the game code. The sound fine if I play them from the command line... Here is the start.wav file: start.zip Edited 2023-09-29 20:25 by fmafma Frédéric |
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| pwillard Senior Member  Joined: 07/06/2022 Location: United StatesPosts: 292 |
Abrupt Clicks not part of the source media are often related to DC coupling in the audio signal. "...any DC present on the connections can potentially cause ... loud clicks or pops when making or breaking connections" Edited 2023-09-30 01:22 by pwillard |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
In this case, it should always occur? And there is a passive filter on the PWM outputs (with 22uF in serie)... Frédéric |
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vegipete Guru Joined: 29/01/2013 Location: CanadaPosts: 1109 |
Are you starting a new sound before the old one has finished playing? Visit Vegipete's *Mite Library for cool programs. |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Nope. Could it be related to the WS2812 bitbanging? I refresh the LED as fast as I can in my main loop... Frédéric |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
Its a wonder it plays at all. WS2812 has to disable all interrupts while it sends the data to meet the timing constraints which could cause all sorts of issues with audio which relies on a regular interrupt of 44100Hx or greater |
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amigawizard Regular Member  Joined: 15/08/2023 Location: AustraliaPosts: 43 |
, Hi Could it be related to the WS2812 bitbanging? I refresh the LED as fast as I can in my main loop... " Rem out the line with bitbang! to see if it fix`s " Wayne ! , |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Ok, I understand! A solution is to re-implement the WS2812 protocole using PIO and DMA... Has anyone already done it? Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Same without the BITBANG! So, this is not the problem... Strangely, the plop only occurs after 3 or 4 sound playing, not right at the begining... Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Mmm, in fact, the plop now also occurs when played from command-line... Even when restarting the board... I'm puzzled! I'll try to play the sounds from drive A:, instead of SD card... Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
It's even worse!!! From drive A:, I can ear some small ticks during the sound playing, and the final plop! The problem occurs on my own board, and on the Maker Pi Pico board. Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
I still have a lot of troubles with the sound output. I connected my board to a little amplifier module based on a PAM8403, and I get horrible noises. I thought it was an issue with my power supply, but even powered from a PowerBank, I can ear the same noises. I hooked up my board output to my PC sound card: here too, I can hear noises, but a little bit less. Here is a capture of the analyse from Audacity. Any idea where the 280Hz noise (and all harmonics) can come from?  Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Hi! I rebooted my project, and I still have issues with sound. I switched to a XPT8871-based amplifier, and I still get the plop at the end of the sounds. But I noticed something weird: I have 250mV DC on the speakers output! So, my tiny speakers are burning hot (but they are still working, even after a entire day playing with the game for a public event)! I think there is a problem with the chip used, in combination with the PWM output. What kind of amplifier do you suggest? I need one which can be powered from 5V... Thanks, Edited 2024-06-19 22:13 by fmafma Frédéric |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
250mV is certainly an excessive offset. With no input both output pins should be close to half Vcc, measured to Gnd. Things to try:- A 0.47µF capacitor in series with the input, in case the onboard one is leaky. Ensure there is no DC path to ground connected to either of the output pins. Last resort is a 470µF capacitor in series with the speaker to block the DC. Positive end to whichever of the two output pins is more positive. |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
There are already capacitors in the low-pass filter outputs, and I don't have any DC offset at the amplifier input. I will try your suggestion, and add capacitors on the spekaers outputs... Thanks! Frédéric |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Hi Frederic, When you use the PWM outputs, they carry DC. The filter removes the PWM frequency, but not the DC. You need a capacitor between the output and the amplifier input. Some audio amplifiers look like dual channel, but are in fact mono channel bridge amplifers. The loudspeaker must be connected between the outputs, and there could be DC on the output, but when it is on both outputs, it is not on the loudspeaker. The XP8871 is in fact a mono amplifier. When there is noise from the PWM outputs, it can be from the power supply ON the pico board itself, and it's frequency and level is changing with the current draw from 3.3V . We solve it by using a linear regulator that bypasses the 3.3V switching regulator (in=Vsys, GND, out=3V3) and put 3V3_enable=low. Regards, Volhout Edited 2024-06-19 23:54 by Volhout PicomiteVGA PETSCII ROBOTS |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
Mmm, I think there is something wrong with my design: I don't have any DC at the output of the filter (as I have a capacitor in serie), but I still have the PWM frequency!!! Edited 2024-06-20 02:35 by fmafma Frédéric |
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| fmafma Newbie Joined: 30/06/2023 Location: FrancePosts: 31 |
What 4.7mH SMD inductor do you suggest? Frédéric |
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