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Thread: Audio board and new teensy 3.6/3.5

  1. #1
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    Audio board and new teensy 3.6/3.5

    Hi, i have backed for 1 3.5 and 1 3.6 unit :-)
    i have a couple questions about the audio board, the first is if the old audio board is 100% compatible with the new teensy line (i think yes)
    and the second is (more technical) with the schemathics here https://www.pjrc.com/store/teensy3_audio.html
    is possible to reproduce the audioboard or you have to load an additional bootloader / firmware?

    thanks

  2. #2
    Senior Member+ Frank B's Avatar
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    Yes, it is 100% compatible, and no, it does not use special firmware.

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    if i want to make my audioboard is possible, amazing! thanks

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    for the SD part, can i use the SD on the new board?
    if yes, which part of the scheme i can take off? and, with the huge power of the new board, is the audio board necessary?

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    Senior Member+ Frank B's Avatar
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    The software for the new slot is not ready yet - dont know when it is
    The audioboard isnt needed, it is just an in or output with some additional features... all the "work" is done by the teensy in software and indeed it works great on a 3.2 with its internal DAC, PWM or S/PDIF or other external DACs without the shield.
    It even can decode mp3 or aac with minimum cpu usage...
    Last edited by Frank B; 08-18-2016 at 04:19 PM.

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    but the DAC on the audio board is better?
    and what the task of the SGTL5000?

    there is some hardware improvement that could be done?

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    Senior Member+ Frank B's Avatar
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    Yes it is better... you might want look at the datasheet :-)
    You need to do this anyway, if you want to make your own board..

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    Thanks Frank B!

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    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by urbanspaceman View Post
    and what the task of the SGTL5000?
    The SGTL5000 is a codec chip, which basically means it has two DACs and two ADCs built into the same chip, and other features like a headphone amp and tons of configurable things.

    In addition to the datasheet, you might take a look at the SGTL5000 docs in the design tool.

    http://www.pjrc.com/teensy/gui/

    On the left side, scroll down until you find the SGTL5000 near the end. When you click it, the docs will appear in the right side panel. If you haven't used the audio lib before, the tutorial PDF and video are meant to help get you up to speed quickly.

    http://www.pjrc.com/store/audio_tutorial_kit.html

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    thanks paul!

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    I built a hand wired breadboard with a socket that can accept a Teensy 3.2 or a Teensy 3.6. It has an audio adaptor mounted next to the universal Teensy socket. I have a 1V/oct synth with 4 VCO's, 2 VCF's and 2 VCA's written entirely in software. I have tried both the T3.2 and T3.6 and both work flawlessly with the audio adaptor in the same hardware. The hardware is pretty simple, encoders, pots, a Teensy and an audio adaptor. Swapping a T3.6 for the T3.2 gives a 20% or so reduction in CPU usage, but for me the necessary benefit is more I/O.

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    SGTL5000 power supply on audio board?

    somewhat on topic... I have a couple of questions about the power supply on the audio board

    The regulator part number on the posted schematic is missing the voltage output parameter... is it 1.5 volts?

    And the bypass caps on the far side of the ferrite bead... is that to bleed off AC from pin 5 off the chip itself?

    The power-supply part count seems pretty high compared with the 'typical application' circuit from the data sheet... is it all really needed if I were to build a mini-audio board with just the CODEC support stuff?

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    Quote Originally Posted by oddson View Post
    somewhat on topic... I have a couple of questions about the power supply on the audio board

    The regulator part number on the posted schematic is missing the voltage output parameter... is it 1.5 volts?

    And the bypass caps on the far side of the ferrite bead... is that to bleed off AC from pin 5 off the chip itself?

    The power-supply part count seems pretty high compared with the 'typical application' circuit from the data sheet... is it all really needed if I were to build a mini-audio board with just the CODEC support stuff?
    What do you mean with "CODEC". I2S?
    If you want I2S, there are other chips, too, most of them work.
    You can output audio without any board.. or with just a LED ("SPDIF")

    edit: oops, sry, miss-understood your question .)
    Last edited by Frank B; 09-12-2016 at 09:22 PM.

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    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by oddson View Post
    The regulator part number on the posted schematic is missing the voltage output parameter... is it 1.5 volts?
    1.8V.

    And the bypass caps on the far side of the ferrite bead... is that to bleed off AC from pin 5 off the chip itself?
    The idea is to low-pass filter the 3.3V supply, so the analog circuitry gets nice low-noise power.

    The power-supply part count seems pretty high compared with the 'typical application' circuit from the data sheet... is it all really needed if I were to build a mini-audio board with just the CODEC support stuff?
    If you want to skimp on the power supply filtering, maybe try replacing that inductor with a wire and remove some of the capacitors, and then listen to see if you believe the sound quality is still ok.

    From a product design point of view, the audio shield is meant to be used together with any number of other possibly very noisy things, like Wiz820io ethernet or LEDs driven by PWM. Adding 1 inductor and a few extra capacitors seemed like a safe approach.

    If you're making a fixed design where people won't be connecting other circuitry to the 3.3V power, maybe you can get by with less power supply filtering.

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    Senior Member oddson's Avatar
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    Thanks Paul. I don't know if it's worth worrying about the cost difference.

    I'm not really used to mixing audio and data so it was the bypass-caps on both sides of the bead that puzzled me.

    I'm thinking a guitar pedal shield for the k66 Teensy might be a nice product.

    Any chance of a k66 that lops off the sd reader?... would make getting it into a stomp-box a bit easier.



    EDIT - found this link helpful on grounding in mixed analog environments http://www.analog.com/library/analog..._grounded.html
    Last edited by oddson; 09-14-2016 at 03:30 PM.

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    Quote Originally Posted by oddson View Post
    Thanks Paul. I don't know if it's worth worrying about the cost difference.

    I'm not really used to mixing audio and data so it was the bypass-caps on both sides of the bead that puzzled me.

    I'm thinking a guitar pedal shield for the k66 Teensy might be a nice product.

    Any chance of a k66 that lops off the sd reader?... would make getting it into a stomp-box a bit easier.
    Sorry if I'm missing something, what is k66?

    In any case, I would be interested in an audio adapter board for the 3.5/3.6 without both the sd reader and the headphone jack. I'm not that good at desoldering things, and having a smaller board would be a plus.

    For a guitar pedal shield a buffer on the input and an SHO (http://tagboardeffects.blogspot.com/...ct-layout.html) or similar boost on the output might be useful.

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    Quote Originally Posted by heuermh View Post
    Sorry if I'm missing something, what is k66?
    MK66FX1M0 (short K66) is the processor of the Teensy3.6

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    Hi,

    I have a similar audio related question for the 3.5, hope I'm not hijacking this thread.

    I'm working on a new design using the 3.5, previously using the 3.2 Teensy. I have the audio running from the DAC on the 3.2 and i'm pulling files from an SD card connected to the 3.2.

    So my first question is, with the 3.5, can I now use the built in SD card for audio?

    Second question, I want to use the second DAC output to drive the control signal of a motor amp, is this possible while using the audio library?

    Cheers

    Matt.

  19. #19
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    Quote Originally Posted by winchymatt View Post
    Hi,

    I have a similar audio related question for the 3.5, hope I'm not hijacking this thread.

    I'm working on a new design using the 3.5, previously using the 3.2 Teensy. I have the audio running from the DAC on the 3.2 and i'm pulling files from an SD card connected to the 3.2.

    So my first question is, with the 3.5, can I now use the built in SD card for audio?

    Second question, I want to use the second DAC output to drive the control signal of a motor amp, is this possible while using the audio library?

    Cheers

    Matt.
    1) yes,
    2) yes

    Upgrade to the latest Teensyduino.

  20. #20
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    Quote Originally Posted by Frank B View Post
    1) yes,
    2) yes

    Upgrade to the latest Teensyduino.
    Thank you!

  21. #21
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    Hi Frank,

    So I have my project built now, but I'm seeing there are issues with using the SD card to play audio files using the Audio lib.

    I have read that the standard "SD.h" does not support the Teensy 3.5 internal SD card, and have managed to get the example code running using the "SdFat-beta" code. However, if I add the Audio library then things start to break, presumably because Audio includes "SD.h" instead of "SdFat.h" as per the "SdFat-beta" Example.

    So you implied this was possible. Am I missing something, or do I need to edit the standard Audio.h library? to get wav playback from SD working again? OF course I could use an external SD card reader on an SPI port, but I've designed my hardware without an external reader, assuming I could use the internal card.

    regards

    Matt.

  22. #22
    Senior Member PaulStoffregen's Avatar
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    The SD card works great on Teensy 3.5 for playing audio. Both of them do. To use the SD card on the audio shield, just run the examples as-is. To use the built in socket on Teensy 3.5, use SD.begin(BUILTIN_SDCARD);

    Months ago, before Teensyduino 1.31, the built in SD card wasn't supported by the Arduino SD lib (and therefore couldn't be used with the audio lib... at least not without major hacking). Version 1.32 fixed access to very old cards. So make sure you're using a newer version.

  23. #23
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    Quote Originally Posted by PaulStoffregen View Post
    The SD card works great on Teensy 3.5 for playing audio. Both of them do. To use the SD card on the audio shield, just run the examples as-is. To use the built in socket on Teensy 3.5, use SD.begin(BUILTIN_SDCARD);
    Perfect, thank you Paul!

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    Quote Originally Posted by heuermh View Post
    Sorry if I'm missing something, what is k66?

    In any case, I would be interested in an audio adapter board for the 3.5/3.6 without both the sd reader and the headphone jack. I'm not that good at desoldering things, and having a smaller board would be a plus.

    For a guitar pedal shield a buffer on the input and an SHO (http://tagboardeffects.blogspot.com/...ct-layout.html) or similar boost on the output might be useful.
    If you're still looking for a board for effects/audio, I have put together a board that I am now starting to sell. The site is still not very good, but it works. Some years ago I made a board I called the OpenEffectsProject. That was based on analog sound controlled by an arduino.
    But now when the teensy is so great I changed! With this board you can test quite much. And it is also made to be inserted into a proper box. Everything is not tested yet, but the basics works fine. www.openeffectsproject.com

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