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  1. If your target signal is only 210-310 Hz,...

    If your target signal is only 210-310 Hz, sampling at 400 kHz does not get you better accuracy. For any reasonable signal-to-noise ratio, you're not going to do better than 1/2 to 1/4 of a...
  2. I made a Mixer8 and offered a Pull Request to...

    I made a Mixer8 and offered a Pull Request to Paul. In the pull request, I also added the Mixer8 to the Audio GUI.

    Of course, he may decline to accept the pull request as he might prefer to...
  3. Agreed, audio library. Also, consider using...

    Agreed, audio library.

    Also, consider using the teensy audio shield.

    Also, if you've never done it before, don't underestimate the challenge of learning the signal processing to actually detect...
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    It would be fantastic if it could be pulled into...

    It would be fantastic if it could be pulled into cores.

    I often help other people develop custom (open source) data acquisition systems using teensy. They really want to be able to pull the data...
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    Yes they are part of teensyduino. Just add to...

    Yes they are part of teensyduino. Just add to the top of your code

    #include <arm_math.h>

    As for learning how to use them, you don't have to prototype your use of vector math operations in your...
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    IMO, you should always first write your code...

    IMO, you should always first write your code yourself without using the CMSIS libraries. Only when you get it working should you introduce the CMSIS functions so as to (maybe) accelerate things.
    ...
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    Using the Teensy 4.1, I just tested quad audio...

    Using the Teensy 4.1, I just tested quad audio out using the two Teensy Audio Shields. Success!

    Interestingly, I was not able to get it to work using flying leads. I had to stack the boards...
  8. If you're not an expert, you're going to want to...

    If you're not an expert, you're going to want to switch to away from the fixed-point filters (and other math) used in the audio library. You'll want to use floating point.

    My Tympan library is...
  9. As for the two channels, this is going back to my...

    As for the two channels, this is going back to my recommendation that you measure the time of the transmitted pulse as well as the time of the received pulse. You had expressed some confusion over...
  10. Regarding the I2S output, I find that the system...

    Regarding the I2S output, I find that the system never operates quite right if I don't have any audio output specified. So, even if I'm not listening to the audio output, I still connect it.

    You...
  11. If the FFT isn't going to work for you, then you...

    If the FFT isn't going to work for you, then you can cascade a few IIR (biquad) filters.

    19990

    You'll need to configure each biquad filter by issuing commands in your setup() function. You'll...
  12. Increasing your frequency to 20 kHz will only...

    Increasing your frequency to 20 kHz will only improve your resolution if you were to move beyond your FFT approach. Unless you're lucky enough to have crazy-high signal to noise ratio, your...
  13. I just looked at your code. It looks like your...

    I just looked at your code. It looks like your tone pulse is 50 milliseconds long?

    If so, that's 2205 samples assuming that you're running at the standard Audio Library rate of ~44100 Hz. ...
  14. How long is your tone pulse? Presuming it is...

    How long is your tone pulse? Presuming it is more than one cycle long, that's going to set your resolution (besides the fft length) not your operating frequency. To get your operating frequency to...
  15. I was intending to imply that the filters be done...

    I was intending to imply that the filters be done in software via the biquad class in the audio library. Definitely not hardware. It requires real skill and/or money to get a good, tight bandpass...
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    Hi, I helped write that driver. I wrote it...

    Hi,

    I helped write that driver. I wrote it because I helped make the Tympan, which is an open source audio processing platform that is a teensy 3.6 at its heart combined with a AIC3206,...
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    Because I didn't know any better, I have also...

    Because I didn't know any better, I have also done the hack of renaming all the classes. What a pain! There has to be a smarter way!

    I'm very interested to hear how other people have dealt...
  18. The reference manual for the processor is not...

    The reference manual for the processor is not helpful...because the missing piece of information is which Teensy pins (which I2S lines) are used by the I2S_quad class. That's the part I can't figure...
  19. Thanks for the quick reply! Where do I learn...

    Thanks for the quick reply!

    Where do I learn which pins the i2s_quad class uses when using with teensy 4? The example sketches (when I looked) provide no hookup guidance.

    Or, to ask a maybe...
  20. Hi! Has anyone had any luck getting I2S quad...

    Hi!

    Has anyone had any luck getting I2S quad to run on the Teensy 4?

    Last fall, I2S_quad wasn't supported yet on the T4, but the T4 was brand new so that's totally understandable! I also see...
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    Oh, and I was surprised by the concern over what...

    Oh, and I was surprised by the concern over what to do about resampling WAV files that are in 44.1kHz when you want them to be in 48 kHz. I mean, resampling is noble, but the current audio library...
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    Based on all the great info here on the forum, my...

    Based on all the great info here on the forum, my floating-point re-write of the Audio Library has both a user configurable sample rate and a user configurable block size (less than or equal to 128)....
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    Frank, Since you've already got your code on...

    Frank,

    Since you've already got your code on GitHub, you can serve it live straight from GitHub using the "Pages" feature of GitHub.

    For example, I've got a floating-point fork of the Audio...
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    Yes! MTP! Chip

    Yes! MTP!

    Chip
  25. My code for computing the IEC1672 coeff is here:...

    My code for computing the IEC1672 coeff is here:

    https://github.com/Tympan/Tympan_Library/blob/master/src/utility/FreqWeighting_IEC1672.h

    And here:
    ...
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    Has there been any success in getting quad I2S...

    Has there been any success in getting quad I2S (quad for both inputs and for outputs) working with Teensy4? If so, has it been folded into the Audio library yet?

    (I tried searching the forum, but...
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    I support KurtE's desire to make a version that...

    I support KurtE's desire to make a version that is more Arduino-like. There is a difference between (1) being able to be compiled in the Arduino IDE and (2) being in the style and typical practices...
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    Definitely still paying attention to this! ...

    Definitely still paying attention to this!

    Thanks for the update,

    Chip
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    @WMXZ, I just got Chris's usb_desc.h entries...

    @WMXZ, I just got Chris's usb_desc.h entries working with your MTP library with SdFat-beta (as you describe) with your example sketch on a T3.6.

    I get both the SD card to appear in Windows *and*...
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    Has anyone been able to get the yoonghm MTP code...

    Has anyone been able to get the yoonghm MTP code to work recently?

    I'm on Arduino 1.8.10 and Teensyduino 1.49. I downloaded the latest Grieman SdFat (not the beta) to go with the yoonghm MTP...
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    So, if we're not overwriting the Teensy3...

    So, if we're not overwriting the Teensy3 usb_desc.h, we're going to get emulated serial, not real serial, right?
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    Also, for use with Teensy 3.6, I assume that I...

    Also, for use with Teensy 3.6, I assume that I copy the "copy-of-core" files over to the Teensy3 core?

    Assuming that this was the right thing to do (and after making the other changes that you...
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    >> Latest version is on GitHub...

    >> Latest version is on GitHub https://github.com/WMXZ-EU/MTP_t4

    Does this generate an emulated serial port or a real one? Browsing the code it seems to generate an emulated one...please correct...
  34. >> I'm an acoustics professor and consultant, and...

    >> I'm an acoustics professor and consultant, and have several Class 1 SLMs and calibrators at my disposal.

    Great! I have this kind of equipment, too. With this equipment, I thought that...
  35. However it is that you implement the software for...

    However it is that you implement the software for your sound level meter, the hard part (IMO) is calibrating the device. There are many choices:

    * You can decide to use a single-point pure-tone...
  36. I'm part of the team that makes Tympan...

    I'm part of the team that makes Tympan, which at its heart is a Teensy 3.6 with an audio codec (and bluetooth module, and LiPo battery plus charger circuit). I did a single-channel and two-channel...
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    Personaly, I always disable that ADC filter as I...

    Personaly, I always disable that ADC filter as I find that it adds unacceptable noise to the system. See my post on this issue here:
    ...
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    The most reliable approach would be to make one...

    The most reliable approach would be to make one oscillator class that has multiple oscillators within the one class. That way, you can do any combination of hard sync, soft sync, or cross-mod that...
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    (double post)

    (double post)
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    When I ported the Audio Library to be floating...

    When I ported the Audio Library to be floating point (for Teensy 3.6), I also added some classes to help with dynamic switching. Our library is under the name "Tympan" and is developed to work with...
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    Hey, this is super cool! It seems to work well...

    Hey, this is super cool! It seems to work well for me on my Teensy 3.6. Thanks for making it happen and for "MTP (Experimental)" getting pulled into the mainline Teensyduino that we all download by...
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    I want a MIDI shield. MIDI In/Out/Through. ...

    I want a MIDI shield. MIDI In/Out/Through. Along with the MIDI hardware, the board should have assorted through-hole solder points for attaching analog sensors or whatever. Nothing fancy, just...
  43. Or, instead of Tympan, you could consider buying...

    Or, instead of Tympan, you could consider buying the BC127 module that's available from Sparkfun and wiring it to your Teensy 4.0 + Audio shield. Or you could consider any other BT Audio capable BT...
  44. I think that the Tympan Rev D...

    I think that the Tympan Rev D will do this.

    The Tympan is aimed at open source hearing aid algorithms, but in reality, it is a general purpose digital audio platform. Full Disclosure: I'm part...
  45. No. But if you can point me to it, I'll learn...

    No. But if you can point me to it, I'll learn something!

    Chip
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    Lowpass filtering at Nyquist is not nearly as...

    Lowpass filtering at Nyquist is not nearly as important for the sigma-delta ADCs used in audio codecs (such as the Teensy Audio board). Try it for yourself...run a frequency sweep into the board, one...
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    Note in my blog post how I show the spectrum of...

    Note in my blog post how I show the spectrum of the self noise with and without the HP filter engaged. My two spectra reveal the chacteristics of the noise added by that HP filter: several very...
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    If you're curious, I did a self-noise analysis of...

    If you're curious, I did a self-noise analysis of the Teensy Audio board for a subset of the audible frequency range (not ultrasound)...
    ...
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    I love to see people getting quantitative....

    I love to see people getting quantitative. Fantastic.

    As some friendly improvements:

    * The term "signal to noise ratio" (SNR) is typically used instead of "contrast". You define what you...
  50. The input impedance to most audio ICs is in the...

    The input impedance to most audio ICs is in the 10-40 kOhm range, which is too low for the output of guitar pickups. Guitar pickups really expect to be plugged into something with at least 500 kOhm...
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