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Thread: Audio shield and Teensy not really working

  1. #1
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    Audio shield and Teensy not really working

    Hello, Im trying to start a project with the audio shield, a couple of weeks ago I bearly got to hear the beeping of the hardware test example code, it was with a lot of noise and it was unstable.

    Now a couple of weeks later I try again to test any of the examples code, but now I just dont get anything out, or in, very frustrating. the shield is new and I now my teensy works properly, any ideas on what could be causing this problem??

    Sometines I get the beep (super noisy and gritty) and after a couple of seconds it just starts to fade out. and then I hear nothing

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  2. #2
    Senior Member PaulStoffregen's Avatar
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    What are you using for listening? Headphones? A stereo system or other electronics with an amplifier?

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    I have tried headphones, my audiointerface (mono input), and also an external speaker with aux input, but I just can't get a normal, stable beep. It's very frustrating. It should work with the shield just placed under the teensy, right?

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Yes, it should work as you've connected it.

    Sometimes connecting to a grounded system can cause this sort of problem, as it effectively shorts the VGND to GND (as the note on the bottom of the shield warns not to do). But it should definitely give good output with ordinary headphones which don't have any connection to ground or other stuff.

    Do you have a voltmeter? All 3 pins of the headphone jack should have approx 1.5 to 1.6 volts DC while it is running, when measuring with the negative lead touching Teensy's GND (or the USB connector shell - often the easiest place to touch when doing these measurements).

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    Do you mean these pins?
    I don't have a voltmeter at hand, but will get one.

    Is it possible that while wiring, touching I burnt the shield or something similar? What should I expect from the voltmeter's result?

  6. #6
    Senior Member PaulStoffregen's Avatar
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    Yes, those 3. You can also access those 3 on pads on the bottom side of the board near the edge.


    Is it possible that while wiring, touching I burnt the shield or something similar?
    Possible by unlikely.

    Usually hardware damage will prevent any sort of sound output.

    Typically corrupted sound is due to a poor ground connection, or shorting or drawing too much current from VGND to GND, or loading the outputs to heavily (eg, an 8 ohm speaker rather than 33 ohm headphones), or a headphone connector not fitting properly, or similar problems.

    Terrible sound can also happen if one of the digital I2S signals isn't connected, but the wires are so close that it couples somewhat by tiny capacitance.


    What should I expect from the voltmeter's result?
    They should read 1.5V to 1.6V if the output circuitry is working properly.

  7. #7
    Senior Member PaulStoffregen's Avatar
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    Looking at your latest photo, I'm wondering if you have actually soldered the pins to the audio shield?

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    Getting it to work even partially is pretty lucky if you're just placing the pins inside the holes without solder! That never gives a reliable connection.

  8. #8
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    Quote Originally Posted by PaulStoffregen View Post
    Looking at your latest photo, I'm wondering if you have actually soldered the pins to the audio shield?

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    Getting it to work even partially is pretty lucky if you're just placing the pins inside the holes without solder! That never gives a reliable connection.
    I have not actually soldered it, because I wanted to prototype it before actually using the teensy. I guess I should just do, and maybe that is the problem I'm facing

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    Even soldered now I don't hear anything more than noise. Don't really know what to do now

  10. #10
    Senior Member PaulStoffregen's Avatar
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    Oh, that's a lot of wires! Are you're sure they're all connected properly?

    Maybe try removing all the non-essential wires. To make sound play, you only need 8 wires: GND, 3.3V, 18, 19, 9, 11, 22, 23.

    I have personally seen those some of those cheap jumper wires have no actual connection. It's a problem that's come up on this forum several times. They are very cheaply made and whoever makes then obviously does not test to verify the really conduct. Try only the 8 required wires, and if it still does not work, assume you have a bad wire and start swapping with other wires. Each time you swap wires, remember to power cycle, since anything wrong with GND, 3.3V, 18 or 19 will cause the audio shield to not initialize.

    For testing, I recommend you program your Teensy with File > Examples > Audio > Synthesis > Guitar. That example makes continuous sound which doesn't depend on any inputs.

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    Click image for larger version. 

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    This also doesn't seem to work.. Is this right? I tried wiring up male and male to be sure there is a connection to the points you mentioned

  12. #12
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    Only to be sure, you are using a Teensy 3.2, right?
    The AudioCard Rev C does not work with Teensy4.0 as wired.

  13. #13
    Senior Member+ Frank B's Avatar
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    ...and these connections are not reliable.

  14. #14
    yeah no offense but these connection and the soldering don't look to good. for now you should get some of these stackable female pinheaders, properly solder them ALL to the audio shield, and then plug the teensy straight in.
    https://www.banggood.com/Stackable-L...t-p-88504.html

    at the very least double check all your solder connections, maybe add a little tin on the skinny looking ones. and then definitely need at least a very basic multimeter to check if your physical connections are ok.

    that being said, i recently had a similar problem where i either ruined the audio board (rev c/t3.6) while soldering or got a rare faulty unit, one of the clock signals was corrupted.

  15. #15
    Senior Member PaulStoffregen's Avatar
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    To make sure it really can work with this sort of wiring, I connected it on my desk here. I can confirm I'm hearing it play the Synth > Guitar example. Here's a few photos.

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  16. #16
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    Quote Originally Posted by PaulStoffregen View Post
    To make sure it really can work with this sort of wiring, I connected it on my desk here. I can confirm I'm hearing it play the Synth > Guitar example. Here's a few photos.

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    So I already triple checked the soldering and connection, they are fine. I also realized I had the 5V pin (Vin on Teensy) connected, which you didnīt, but I assume this should not be a problem.

    I metered all the voltages from the 3.3 pin on the teensy to the other pins, and to the cables soldered to the shield, and all the cables work properly. Except pin 18 and 19. They didn't show any voltage, not even on the teensy self. Any ideas on what the problem might be here? The teensy could be damaged maybe?

  17. #17
    Senior Member PaulStoffregen's Avatar
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    Pins 18 and 19 should definitely measure 3.3V (when the voltmeter's negative is connected to GND). Pins 18 and 19 are signals SDA & SCL, which are connected to 2K resistors on the audio shield. Both resistors connect to the 3.3V line. You voltmeter should see 3.3V on those pins, except during moments of communication to set up the audio shield, when they'll fluctuate momentarily, but still should remain close to 3.3V because the communication is so brief and voltmeters average over fairly long time to show you a steady reading.

    If you remove the wires for 18 and 19, those 2 pins should be at 3.3V on the audio shield side. They should be at some fairly low voltage on the Teensy 3.2 side, because the resistors which bring them up to 3.3V are on the audio shield.

  18. #18
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    Quote Originally Posted by PaulStoffregen View Post
    Pins 18 and 19 should definitely measure 3.3V (when the voltmeter's negative is connected to GND). Pins 18 and 19 are signals SDA & SCL, which are connected to 2K resistors on the audio shield. Both resistors connect to the 3.3V line. You voltmeter should see 3.3V on those pins, except during moments of communication to set up the audio shield, when they'll fluctuate momentarily, but still should remain close to 3.3V because the communication is so brief and voltmeters average over fairly long time to show you a steady reading.

    If you remove the wires for 18 and 19, those 2 pins should be at 3.3V on the audio shield side. They should be at some fairly low voltage on the Teensy 3.2 side, because the resistors which bring them up to 3.3V are on the audio shield.

    So, I bought a new teensy 3.2, tried it, checked al the pins voltage, also at the end of the jumper cables, and they seem to work with the proper voltage. But still, when I upload the guitar and put on my heaphones, I just don't hear anything. My only idea now is that the audio shield is damaged. Which would be weird as it is pretty new.

  19. #19
    Senior Member+ Frank B's Avatar
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    Quote Originally Posted by Skester96 View Post
    So, I bought a new teensy 3.2, tried it, checked al the pins voltage, also at the end of the jumper cables, and they seem to work with the proper voltage. But still, when I upload the guitar and put on my heaphones, I just don't hear anything. My only idea now is that the audio shield is damaged. Which would be weird as it is pretty new.
    See post#6

    Just give the intended, often used and tested connection a chance. It's proved to work reliable. Male+female pinheaders - without wires. Maybe it helps?
    Even if not - you'll know if one of the boards is the problem.

  20. #20
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    Quote Originally Posted by Frank B View Post
    See post#6

    Just give the intended, often used and tested connection a chance. It's proved to work reliable. Male+female pinheaders. Maybe it helps?
    Even if not - you'll know if one of the boards is the problem.
    After that you can still use your chinawires.

    Yeah that was with corrupt sound which I had. Now I just have no sound

  21. #21
    Senior Member+ Frank B's Avatar
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    That does not change my proposal.

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    So I just checked with the voltmeter the direct connections on the audio shield, so I'm pretty sure data and voltage connections are properly wired and connected, but I still I can't hear anything.
    Should I already assume the audio shield is broken? Don't even know what to test anymore.

  23. #23
    Senior Member DD4WH's Avatar
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    Solder your boards together, or do it like Frank proposed in post #19 and #21
    It is highly likely that your wires do not give reliable contact.

  24. #24
    Senior Member PaulStoffregen's Avatar
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    Are pins 18 and 19 still showing no voltage?

    If so, try measuring the 3.3V power on the bottom right corner behind the headphone jack, of course with the multimeter negative lead touching the USB cable shell or other GND location on Teensy.

    No 3.3V reading on SDA and SCL probably means the audio shield isn't getting 3.3V power, because the shield has 2 resistors for those pins which bring both up to 3.3V.

  25. #25
    Administrator Robin's Avatar
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    You've done a lot of work here and we want to help you out by sending you an audio shield with sockets. Do not solder anything to the pins on your Teensy so that you can plug it into the sockets on the audio shield when you receive it.

    The audio shield will have these sockets soldered on to it. - https://www.pjrc.com/store/socket_14x1.html
    These are the sockets we recommend using with the Audio Shield and a Teensy With Pins.

    Check your email that you used to sign up on the forum. You should have a email from me.

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