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  1. Replies
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    Personally, I like using Arduino/Teensy to *add*...

    Personally, I like using Arduino/Teensy to *add* functionality to old synths.

    Back when I got my Korg Polysix, they were pretty undesirable and inexpensive due to the leaking battery problem...
  2. I think that I found the issue. The OCT version...

    I think that I found the issue. The OCT version of AudioOutputI2S gave me an important clue...

    Here is the quad version:



    #if 1
    memcpy_tointerleaveQuad(dest, src1, src2, src3, src4);...
  3. Sweet guidance. Will do!

    Sweet guidance. Will do!
  4. Hi Paul, Yeah, I saw that. When I copied that...

    Hi Paul,

    Yeah, I saw that. When I copied that into my Float32 extension of this class, and adjusted all the data types, it doesn't work on T4. It successfully works fine on T3.6 and sounds fine....
  5. AudioOutputI2SQuad and memcpy_tointerleaveQuad

    I'm trying to understand the interleaving that is done with the audio samples in the AudioOutputI2SQuad class. Looking at the isr() method, I see that it calls the memcpy_tointerleaveQuad, which is...
  6. If you're using a teensy 3.5 or 3.6 (and possibly...

    If you're using a teensy 3.5 or 3.6 (and possibly T4.x), you can use one of the floating-point versions of the teensy audio library from the community. There are several out there.

    The two that...
  7. Replies
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    Paul's comments about price are spot on. Once...

    Paul's comments about price are spot on. Once you add all the features that you really want (a better audio codec, extension for more channels than stereo, audio jacks, BT module, LiPo recharging, a...
  8. I, too, have seem massive variation in write...

    I, too, have seem massive variation in write times to the SD card. It seems to depend a lot on the SD card itself. It is also affected by how they are formatted.

    So, after a bunch of experiments...
  9. CPU Cycle Counter Formula in AudioStream

    I love how the Audio library lets you see what fraction of the processor is being consumed by different blocks in your audio processing chain. But, in looking at the formula, I don't understand how...
  10. Replies
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    The OpenAudio library is a collaboration between...

    The OpenAudio library is a collaboration between me and Bob Larkin. Since I don't recognize the file "DSP_Teensyduino_32.h", I'm assuming that it's something that Bob added. If it fails to compile...
  11. Replies
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    496

    Formant shifting and pitch shifting are indeed...

    Formant shifting and pitch shifting are indeed different things. My links are for formant shifters that work in the frequency domain. They move the amplitude of the FFT bins up or down but leave...
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    Moving all the formants up and down isn't...

    Moving all the formants up and down isn't particularly difficult...if you've already got a frequency-domain processing algorithm stack going. Getting the round trip FFT/IFFT processing needed to...
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    If you're going to try to implement...

    If you're going to try to implement frequency-domain noise reduction, be aware that the Teensy 3.2 will probably not be fast enough to do a round-trip FFT->IFFT in order to do the frequency-domain...
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    Github (or similar) is definitely the way to go. ...

    Github (or similar) is definitely the way to go. If you've never used a version control system before, it's not a trivial thing to get into, but it is totally totally totally a skill worth having.
    ...
  15. Regarding SD recording, you can use the Tympan...

    Regarding SD recording, you can use the Tympan software library with anyone's hardware, as long as it is a Teensy 3.5 or Teensy 3.6. The library is a floating point extension of the Teensy Audio...
  16. Regarding the Tympan, it already has the Teensy...

    Regarding the Tympan, it already has the Teensy 3.6 built into it. We buy the Teensy 3.6 bootloader from Paul (the maker of Teensy) and use the same processor and all that. Therefore, it *is* a...
  17. While the Teensy Audio Shield is amazing for its...

    While the Teensy Audio Shield is amazing for its price, there are alternatives if you want better performance...

    * Blackaddr has his "Teensy Guitar Audio Shield". IMO, it sounds much better than...
  18. Replies
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    Oh, so we *are* talking about frequency domain...

    Oh, so we *are* talking about frequency domain processing. When I measured FFT vs FIR based processing on the T3.6 using the ARM CMSIS Float32 library, FIRs are more efficient up to around 96...
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    I'm a bit confused by your statement "in order to...

    I'm a bit confused by your statement "in order to substitute the standard FIR filtering with convolution filtering". When convolution is done in the time domain, convolution *is* FIR filtering,...
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    To partly answer my own question, I know that...

    To partly answer my own question, I know that long FIR filters can have a role in creating reverb/echo effects. For example, if you want to go out and actually measure the reverb/echo in a real...
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    Regarding this side-track about super-long...

    Regarding this side-track about super-long FIRs...why would someone want a 65536-tap FIR for audio processing? Even running at a 96 kHz sample rate, this gives a resolution of about 1.5 Hz (or maybe...
  22. Replies
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    You said that you wanted to be able to change the...

    You said that you wanted to be able to change the block size...

    In my Float32 extension of the Audio library (for our "Tympan" project), I made the blocksize adjustable. While I did not make the...
  23. The existing envelope class is written for fixed...

    The existing envelope class is written for fixed point math (as is the rest of the audio classes), which makes it hard for me to see what it's doing. It also makes it hard for a person like me to...
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    If you use a regular delay with a fixed dealt...

    If you use a regular delay with a fixed dealt time (like is currently in the library) you would get a more 'analog-style' delay if you could smoothly vary / modulate the sample rate of the whole...
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    The short answer (which is not helpful) is that...

    The short answer (which is not helpful) is that you can do anything you want...but it could take a lot of development and effort.

    The longer answer is that you could modify the delay class to...
  26. Hi folks, As usual, that version of my float32...

    Hi folks,

    As usual, that version of my float32 library isn't updated very often as all of my active development is in the Tympan repo:

    https://github.com/Tympan/Tympan_Library

    The Tympan...
  27. Thanks, everyone for the suggestions and the...

    Thanks, everyone for the suggestions and the photos. With this help, I got it to work!

    I disconnected my wiring for Pin6 and made my wiring look more like Paul's. Digital values were clearly...
  28. Both boards now have their 10K resistor removed. ...

    Both boards now have their 10K resistor removed. Sadly, I'm still not able to get the 2nd audio board to acquire audio. :(

    20406

    Any other suggestions for something that I can try?

    Or, if...
  29. Thanks for all the deep digging! I did remove...

    Thanks for all the deep digging!

    I did remove the one board's 10k resistor and it didn't work. I'll try removing the other board's resistor. Good idea. Sadly, I'm separated from my hardware and...
  30. Second attempt at attaching pics... 20351 ...

    Second attempt at attaching pics...

    20351

    20352
  31. For those more visually-inclined, here are the...

    For those more visually-inclined, here are the mods described in another form:

    20336

    20337
  32. Teensy 4.1 and 4-channel audio (AudioInputI2SQuad)

    I'm still trying to get my T4.1 (beta) to do 4 channel audio using two of the RevD Teensy Audio Shields. I'm successful in getting audio output of the system, but I can't seem to get audio into the...
  33. Signals with a wider bandwidth will definitely...

    Signals with a wider bandwidth will definitely help improve your resolution. But it might make detection harder (as a human trying to see what's going on while debugging).

    What would really help...
  34. This is a question of resolution vs accuracy. ...

    This is a question of resolution vs accuracy. Having a higher sample rate will give you an answer with more decimal places (ie, higher resolution), but those extra decimal places are not reliable or...
  35. 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...
  36. 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...
  37. 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...
  38. Replies
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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...
  39. Replies
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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...
  40. Replies
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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.
    ...
  41. Replies
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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...
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  47. 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. ...
  48. 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...
  49. 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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