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Hissing sound during and after playing wave file

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  • ESPsupport
    replied


    Well, that doesn't make much sense.



    What comes from Audio is PWM, the Touch could only introduce AM noise on the audio line.



    The 74LC08 (with clean 'analogue' power) should completely remove any AM noise on the PWM.



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  • Pulsart
    replied


    Yes, when I disable touch, the noise stops.

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  • ESPsupport
    replied


    Are you saying the noise is there only when touch is turned on?

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  • Pulsart
    replied


    Thank you for the tip, but can't make it work properly either.
    I unsticked the LCD with the touch-screen to see if this noise was induced by the touch-panel itself, but it appears not to come from it directly.
    One issue I see is that on the Picaso chip, the two pins YD and XL for the touch panel are just nearby the audio output pin. And as the refreshment of the touch panel is about 1kHz, it is induced by crosstalk in the audio at his point and all along up to R21. I also noticed that the capacitors C28 and C30 (on XR and YU lines) are not mounted, but this does nothing.
    Is it possible to diminish the refreshment frequency of the touch panel?

    Leave a comment:


  • ESPsupport
    replied


    If you want to you can try this.



    Connect side of R21 that heads off towards the Picaso Chip, to, say, the joined inputs of a gate from a 74LC08 (with clean 'analogue' power, or at least well decoupled with eg 470r/4u7).



    Connect the output of that gate to a string of three 2k2 resistors and connect each of the resistor joins to gnd via 0.01uf.



    Connect the last 2k2 to your amplifier

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  • Pulsart
    replied


    Hi, I have the same hissing problem using the uLCD24-PT, but using the direct audio output, not the on-board amplifier. The problem is that the direct output CANNOT be disabled using the pin_HI(AUDIO_ENABL); command. The audio output is just UNUSABLE as is for my application!!!
    Do you have another solution, maybe by replacing or adding some componets?
    I personnaly think that this is a terrible hardware design issue and I can't understand why it has not been fixed in the latest hardware versions. I have tried with a uLCD-32032-P1T I bought more than two years ago and the problem is the same!!! So please FIX this problem for next hardware version, thank you very much.

    Leave a comment:


  • meldavia
    replied


    The audio amplifier is left turned on after any sample is played, this is done
    to substantially eliminate clicks between samples. Unfortunately, the action
    of scanning the touch pad generates a lot of audio hash which is picked up by
    the amp. Manually disabling the audio amp when you have finished playing should solve this.

    pin_HI(AUDIO_ENABL); // turn off audio amp.

    Amp will be automaticaly turned back on next time you play a file.

    Leave a comment:


  • masterix275
    replied


    Any news?

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  • ESPsupport
    replied


    Sorry, missed the bit about touch. Will need to investigate.

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  • masterix275
    replied


    Sorry to be a pain, but could you please be more specific?

    I've just tested it a bit and it looks like the hissing is present only when the touch function is enabled. I don't think this has been mentioned in the thread?

    Thanks

    Marek

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  • ESPsupport
    replied


    Read the rest of this thread, the answer (and explanation) are there

    Leave a comment:


  • masterix275
    replied


    wkorosec wrote: Hi,
    I have a very strange and annoying sound effect on my uLCD-24PT:
    When playing a wave file, you can hear the recorded sound, but it is overlaid with a high frequency, hissing tone. This hissing sound continues even after the wave file has finished playing.

    The input files are Windows-Wave Files generated by a Text 2 Speech program.
    RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

    I tried out different loudspeakers (8Ohm), but no luck.

    Version 0.000 [56 00]
    Get Status 0.016 [7A]
    Version 0.109 [56 01]
    Micro-LCD
    Hardware Revision: 10
    Firmware Revision: 19
    H res: 240
    V res: 320

    An acceptable quality of the sound output is really important for my project ...

    Best regards & many thanks for your help in advance !
    Wolfgang
    Hi, I have very similar "hissing" problem with my uLCD-32PT_GFX2. The actual sond is fine but I get also the hissing in the background. It starts (the hissing) just before the actual wav and then just keeps hissing until system reset. The thing is though that I'm using sound files which meet the requirements (supplied by 4D Systems). Another interesting thing is that when the touch function is disabled the hissing stops but it restarts once the touch function is reactivated.
    Only reset stops the hissing...

    The idea is to play a little sound every TOUCH_PRESSED...

    Any help would be greatly appreciated...

    Thanks

    Marek

    Leave a comment:


  • Dancy
    replied

    found a bug in the WaveDemo.4dg program, line 151 should be un-remarked and line 152 should be remarked. Otherwise all of your wave files on the chip look just like DING.wav
    Also in the following program:
    Code:
    #platform "uLCD-32PT_GFX2"func main()snd_Volume(127);print("\nstart.\n") ;pause(5000);file_Mount();print("\nNow Playing\n") ;file_PlayWAV("POLICE.WAV");pause(5000);snd_Stop();print("\nstop.\n") ;file_Unmount();pause(5000);endfunc
    the hissing noise begins right after POLICE.WAV finishes playing and does not stop untill 'endfunc'. Any other way to turn it off?

    Dan Clemens

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  • Dancy
    replied


    running windows 7 (grin) but will try it in XP mode and thank you for the utility!

    Dan

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  • ESPsupport
    replied


    Upgrade to XP XP tells you the sample rate

    I'm sure there should be (free) utilities out there that give you that information.

    http://www.4dsystems.com.au/code/index.php?node=77&id=85 is a 4DGL utility that tells you

    Leave a comment:

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