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  1. Two possibilities: #1 When you adjust delay,...

    Two possibilities:

    #1 When you adjust delay, you are still jumping between discrete delay times (resolution 1/44100 seconds) which in itself causes aliasing. When people design chorus/flanger...
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    Many of the Teensy's have a built in ADC, though...

    Many of the Teensy's have a built in ADC, though it's only 12-bit. Many people use it for audio when they don't need high quality. Are you using a Teensy 3.5/3.6 and running out of pins? If not,...
  3. I'm actually a hardware guy. :) 5 years...

    I'm actually a hardware guy. :)

    5 years digital ASIC design, 11 years FPGA and electrical schematic/PCB design. It's only the last few years (about 3) I've shifted to software as the work I do...
  4. I see both shift operators and bit functions a...

    I see both shift operators and bit functions a lot, neither is particularly readable or less readable to me. The IMPORTANT thing is to not use magic numbers in your code.


    // GOOD, because the...
  5. Even with the pot not moving, the analog read...

    Even with the pot not moving, the analog read value will still be jumping around a lot due to noise, which is the same as twitching the knob back and forth randomly at high speed. Are you filtering...
  6. You can get distortion when adjusting the delay...

    You can get distortion when adjusting the delay because you are violating the Nyquist rate. It only occurs when changing the delay value?

    If so, this can happen because Nyquist sets a limit on how...
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    Thanks KurtE, I was not aware of that particular...

    Thanks KurtE, I was not aware of that particular transfer() function, I'll go look into it. As for the the cache issue, should not the pointers to the buffers be volatile? In fact, shouldn't this be...
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    @KurtE You're pretty knowledgeable about SPI and...

    @KurtE You're pretty knowledgeable about SPI and DMA. I think you also worked on the T4 beta? What do you think are the odds of us getting SPI DMA support built right in the teensyduino libraries (as...
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    Luckily, it can be changed on the fly! To explain...

    Luckily, it can be changed on the fly! To explain a little, the output driver (PAD register) settings are done on a per-pin basis rather than 'function' basis. Each pin can be configured for several...
  10. Be aware the 45 MHz parts have a dummy cycle...

    Be aware the 45 MHz parts have a dummy cycle between the address and the data. The 20Mhz parts don't have that
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    @DD4WH: The assignments can likely go anywhere...

    @DD4WH: The assignments can likely go anywhere after you've called Wire.begin() for I2C, during my testing I had them at the end of setup(). The I2S stuff starts up as soon as the I2S object is...
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    In general this is true. But you also need to...

    In general this is true. But you also need to consider PCB routing. Tracks with fast edges can couple into adjacent tracks where then run close and parallel. Thus, data lines that run right next to...
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    Hey Paul or anyone from the Beta who worked on...

    Hey Paul or anyone from the Beta who worked on I2C/I2S, question about this resistor. At first, I couldn't get my T4 working with my WM8731. As we already know, the WM8731 is sensitive to overly fast...
  14. There's actually a new 4Mbit SPI now so no need...

    There's actually a new 4Mbit SPI now so no need for FRAM if that's enough capacity. Check out ISSI IS62WVS5128
  15. Will it work? Yes and no. #1) They require a...

    Will it work? Yes and no.

    #1) They require a bit of startup work. You must hold SCLK low and CS# high during power on sequence, then issues a couple custom commands to reset the device. Not a big...
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    In this algorithm you are not using the same...

    In this algorithm you are not using the same values over and over again so they can't be precomputed like for wave synthesis. You are taking the input complex phasor and multiplying in by another...
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    I was working on a pitch shifter for the T3.6...

    I was working on a pitch shifter for the T3.6 that implements the Ocean's pitch shifting algorithm. It is a spin on the concept of the phase vocoder. The basic process is

    1) Use overlapping STFT...
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    Thanks Paul. Very much looking forward to using...

    Thanks Paul. Very much looking forward to using the Teensy 4.0 with my TGA Pro and this info will help me make an adaptor board. I presume the 100 ohm resistor on MCLK was to help absorb some...
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    Teensy 4.0 I2S Support

    I understand that the T4 is not direct pin compatible with the audio shield as the I2S pins are in different locations. Looking through the massive Beta thread, there was some discussion about an...
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    Assuming the SSOP part, Pin 22 (CSB) of the...

    Assuming the SSOP part, Pin 22 (CSB) of the WM8731 controls the I2C address. Pin 21 (MODE) controls whether it is I2C or SPI control interface. For two WM8731s, pull or tie the MODE pin low on both...
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    Kicad is great

    Kicad is great
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    Yes, use a sine wave. When I made my chorus I got...

    Yes, use a sine wave. When I made my chorus I got it working glitch free with a sinewave first, then moved on to investigating ways of bandlimiting the other waveforms like triangle.
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    Don't worry! We're hear to help. You might...

    Don't worry! We're hear to help.

    You might also want to try something dead simple first. Rather than designing a proper BiQuad IIR filter, what about just a 1st order IIR where you have



    //...
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    You can't use a raw triangle wave as a modulation...

    You can't use a raw triangle wave as a modulation source directly, it will cause glitching because a perfect triangle has infinite bandwidth due to discontinuities at the peaks/troughs. This infinite...
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    Earlier this year I was working on a chorus for...

    Earlier this year I was working on a chorus for my BALibrary. In order to get the chorus sounding right with no glitches, I had to do exactly what Chip says here. You cannot use a static delay value...
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    What types of sources to you plan to connect as...

    What types of sources to you plan to connect as audio inputs, and what you want to connect the output to?
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    Hi Paul, I'm not quite sure exactly which "ext"...

    Hi Paul, I'm not quite sure exactly which "ext" in the schematic you're referring to? Here's a summary of a couple items for Bob's benefit, but let me know if I'm stilling missing the "ext" you were...
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    I also did a WM8731 audio board for the Teensy....

    I also did a WM8731 audio board for the Teensy. Mine is significantly larger because I added a lot more functionality including a preamp (to support instrument/mic level inputs), MIDI and connectors....
  29. I went to great lengths to reduce all forms of...

    I went to great lengths to reduce all forms of noise when designing my Teensy Guitar Audio Board. It requires a lot of considerations including:
    - all audio grade, low-noise components in the audio...
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    I've used JUCE to interact with my Teensy. I've...

    I've used JUCE to interact with my Teensy. I've released an application for it and posted about it on this forum here.

    The application has nothing in it specific to Teensy, it's just a graphical...
  31. In the thread linked above, I had reported a...

    In the thread linked above, I had reported a trick for disabling and renabling the BCLK of the I2S bus. You can disable the bus, do your I2C config, then renable the I2S bus.

    // On the T3.6:...
  32. DerekR, Just to confirm, even if you use the...

    DerekR,

    Just to confirm, even if you use the I2C bus with no I2S elements in the code, you still see errors? I found I could eliminate the I2C errors by removing I2S entirely from the build.
    ...
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    Try running your Teensy at a lower frequency (96...

    Try running your Teensy at a lower frequency (96 MHz or less) via the IDE. I also found lots of problems with I2C errors on WM8731. Two things made a huge improvement.
    1. Turn the Teensy clock down....
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    I don't see any obvious difference vs my design...

    I don't see any obvious difference vs my design for the I2S/I2C lines other than the pullups for I2C. 4.7K is a little weak for 3.3V, mine are in the 2K range. This shouldn't be a big problem though....
  35. I've seen USB audio issues discussed at length in...

    I've seen USB audio issues discussed at length in a couple different threads including a detailed one with Paul and FrankB though that was addressing clicks, rather than high pitch noise harmonics....
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    As mentioned above, my BALibrary...

    As mentioned above, my BALibrary uses the WM8731 in slave mode. I provide a replacement for the default AudioControlWM8731 called BAAudioControlWM8731. It provides some robustness enhancement on the...
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    I've found use for the external memory for some...

    I've found use for the external memory for some more complex effects, particularly for Sound-On-Sound which is admittedly still delay based though. All the effects in BALibrary use DMA SPI for...
  38. Thread: Midi

    by Blackaddr
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    If the device only has USB, you would need...

    If the device only has USB, you would need something to act as a HOST and can recognize USB MIDI Class compliant devices in order to extract the data, then send it out a serial port instead.

    You...
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    Thanks! Paul did such an amazing job with his...

    Thanks! Paul did such an amazing job with his Audio library making it super easy for people to get started with audio projects in general, I was thinking what might the next step be?

    Having some...
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    New audio effect: TREMOLO

    I've added a new effect to BALibrary: Tremolo

    The effect has the following controls: bypass, rate, depth, volume.

    Like all the other effects in the library, AudioEffectTremolo supports runtime...
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    Just to reinforce what the others have said, if...

    Just to reinforce what the others have said, if you have the opportunity to adjust pitch when the sound is generated, DO IT! Pitch-shifting audio samples after synthesis is one of the most...
  42. To get decent performance you'll probably need to...

    To get decent performance you'll probably need to use DMA SPI to work with the serial memory. I modified crteensy's DmaSpi library to work with LC1023 memories here.
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    Looks pretty cool with the wood grain finish.

    Looks pretty cool with the wood grain finish.
  44. New convenience class for physical audio controls

    I've created a class BAPhysicalControls to make it easier to manage physical controls in audio projects including pots, rotary encoders, switches and outputs (LEDs/relays).

    By having controls...
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    What kind of issues arise with USB due the...

    What kind of issues arise with USB due the non-ideal sample rate? How do they manifest in the sound? I've tried USB before and had some fidelity issues but never delved to deep into why.
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    I've designed an advanced audio board (TGA Pro)...

    I've designed an advanced audio board (TGA Pro) for the Teensy using a WM8731. The codec is the slave, Teensy is the master so all the other Teensy peripherals work correctly. You can find the...
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    The way the author designed it, as is, no you...

    The way the author designed it, as is, no you can't. However, you can always modify it to your liking, by adding proper bypass control.
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    Regarding switches and lipo, as long as it it...

    Regarding switches and lipo, as long as it it doesn't change the size or increase the cost! The challenge Paul has I'm sure is he can't satisfy everyone. In general, I think people would rather have...
  49. Awesome! I love seeing Teensy guitar stuff! It's...

    Awesome! I love seeing Teensy guitar stuff! It's truly the best platform I've found for this type of realtime audio processing effects.
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    Finally getting back to this project while I wait...

    Finally getting back to this project while I wait for my next production batch of TGA Pro audio shields to come in.

    14394 14395

    I've mostly been writing platform code for the MIDI controller....
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