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  1. You can process the triangle or sawtooth with an...

    You can process the triangle or sawtooth with an IIR filter (look at the CMSIS biquads supported by teensy for accelerated filtering) or use the waveform approach. The latter is is certainly more...
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    Sorry for the very late reply, I missed this...

    Sorry for the very late reply, I missed this message a month ago. To answer you question, if you just want line in, the schematic in the datasheet is suitable. If you want really good noise...
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    The Teensy Audio library supports other codecs as...

    The Teensy Audio library supports other codecs as well. Take a look at any of the control_* files. Those are your options without having to write your own stuff....
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    I've not tried C++17 yet, but I know for sure...

    I've not tried C++17 yet, but I know for sure C++14 is supported fairly well by Teensyduino and for a while now so I would start with that to use something with some more maturity on Teensy. I use a...
  5. Yes, the Teensy 4.1 should be pin compatible with...

    Yes, the Teensy 4.1 should be pin compatible with the primary pins it shares with the Teensy 4.0. I've already ordered a few Teensy 4.1s so I'll be able to confirm everything works with the TGA Pro...
  6. If I recall correctly, you also have a TGA Pro. I...

    If I recall correctly, you also have a TGA Pro. I made an adaptor for people wanting to use the Teensy 4.0 with it.

    https://www.tindie.com/products/Blackaddr/tga-pro-teensy-40-adapter/
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    That number actually sounds spot on to me. The...

    That number actually sounds spot on to me. The SNR spec for the WM8731 is 90 dB on the ADC. Using the 6 dB-per-bit rule, this is 90/6 = 15 bits of usable noise-free bits in an ideal scenario. In...
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    I think you're being a little harsh on this...

    I think you're being a little harsh on this CODEC. All codecs from reliable manufacturers can meet their datasheet specs, but rarely do in a system because it's the design of the system around it...
  9. You are correct, the purpose of this is to fix...

    You are correct, the purpose of this is to fix the direct-DMA capability with the audio buffers which is only broken on the T4. There's no pressing need to make a similar change to the other...
  10. Let me know if you have any problems with the PR...

    Let me know if you have any problems with the PR and I'll look into it. If you also have any ideas on how to accomplish the same thing in a cleaner or more-portable, future-proof way I'd love to hear...
  11. You are right. If we wanted AudioStream to be...

    You are right. If we wanted AudioStream to be more future-proof, we need to have at least two objectives:
    - separate the control information (meta data) from the audio data. This could be done with...
  12. You can use my pull request for cores/teensy4...

    You can use my pull request for cores/teensy4 as-is and it should work for your user code, but you must also make a change in the Audio library, effect_freeverb.cpp to compile. There is a nasty bit...
  13. It's more than just a speed difference. My...

    It's more than just a speed difference. My particular issue is backwards comparability. Teensy 3.X permits to you DMA directly in and out of Audio buffer because that processer only as a 4-byte...
  14. Hey Paul, I created a pull request to illustrate...

    Hey Paul, I created a pull request to illustrate a potential solution to this problem. The method is to replace the audio data buffer array in audio_block_t with a pointer. This makes the change...
  15. I spent a lot of effort designing my Teensy audio...

    I spent a lot of effort designing my Teensy audio shield to be low noise, hi quality. It's a very difficult task to keep mixed signal (digital and analog) designs noise free on the analog side. You...
  16. Can you use a USB midi dongle connected to the...

    Can you use a USB midi dongle connected to the host? This will show up as an available USB MIDI device to JUCE, then talk to the Teeny over the usual MIDI connectors.

    Example USB midi dongle
    ...
  17. There is a way to restructure the metadata in a...

    There is a way to restructure the metadata in a fairly backwards compatible way. I tried this out and it it worked on my setup.

    1) Modify the audio_block_t to contain (int16_t*) instead of a fixed...
  18. The aversion to memcpy is every single word...

    The aversion to memcpy is every single word copied takes multiple CPU instructions from the various load-stores. At 44 Khz, you're talking a couple hundred thousand instructions per second for a...
  19. Thanks WMXZ for taking the time to read and...

    Thanks WMXZ for taking the time to read and comment, the help is appreciated.

    I looked over the output_i2s.cpp, you're right WMXZ, the output_i2s.cpp creating a local 32-byte aligned i2s_tx_buffer...
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    You might want to create your own separate...

    You might want to create your own separate project thread for discussing your mixer design, it may get more views that way.
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    I don't think you're missing anything. Memory...

    I don't think you're missing anything. Memory comes down capacity, latency and throughput (let's ignore power for now). So I guess it comes down to how much of your customer base needs something...
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    ISSI is probably the cheapest alternative (well,...

    ISSI is probably the cheapest alternative (well, a little bit cheaper than Cypress) ignoring all the Chinese-only market stuff. You can get 64Mbit for about $5 USD in production quantities. Would I...
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    FORM FACTOR - keeping the T3.6 form factor would...

    FORM FACTOR - keeping the T3.6 form factor would be great

    RAM - adding a big chunk of reasonably fast ram would be ideal. A single HyperRAM chip on board would be my suggestion in 64Mbit or...
  24. Once again, thanks for your time Paul. - just to...

    Once again, thanks for your time Paul.
    - just to be clear, please note my suggestion is the AUDIO_BLOCK_SAMPLE sized audio data buffers (audio_block_t.data) must be be 32 BYTE aligned for DMA, not...
  25. Hi Paul, thanks for the reply. I've looked at the...

    Hi Paul, thanks for the reply. I've looked at the cache functions in quite some detail as I've been investigating this issue for about 2 months so I'm happy to wait a few more weeks. I've also had...
  26. Any developers who contributed to the Audio...

    Any developers who contributed to the Audio library or DMA development care to comment on this? I'd like to get some validation or discussion before submitting a bug report on github.

    Once again,...
  27. I've been looking at lot at the T4 memory...

    I've been looking at lot at the T4 memory structure lately as i've been having problems with cache coherency.

    @defragster, perhaps you can clear up any misconceptions.

    I'm pretty sure the TCM...
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    You can also use SPI ram for delay. My audio...

    You can also use SPI ram for delay. My audio board uses 4Mbit chips. One of these chips gives about 6 seconds of single-channel delay, the equivalent of 2048 audio blocks. You can use the SPI...
  29. Cool! In order to use the built-in allocate() and...

    Cool! In order to use the built-in allocate() and release() functions (which would let you avoid implementing a pool manager) you must inherit the AudioStream class, otherwise you'll need to hack the...
  30. Okay, I was able to reproduce this issue with the...

    Okay, I was able to reproduce this issue with the Teensy Audio Shield. Maybe someone with a working Teensy 4.0 and audio shield using LINE IN left can give this a try?

    The sketch is written to...
  31. Teensy 4.0 problem with DMA to/from OCRAM interacting with Audio library

    After months of struggling to get DMA SPI memory working with the T4 OCRAM I think I finally found the problem, and I think it's in AudioStream.h. Basically, I'm getting audio buffer corruption when...
  32. SPI1 with DMA is only supported on 3.5/3.6/4.0

    SPI1 with DMA is only supported on 3.5/3.6/4.0
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    I'm not sure how you could possibly think you got...

    I'm not sure how you could possibly think you got scammed. Mixed signal (analog and digital) design is tough, period. The built-in ADC is not intended for high quality audio applications like guitar...
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    The schematic is available for free in the...

    The schematic is available for free in the datasheet found on the product page. You are welcome to take a look at the preamp and analog power design for use in your own circuit.
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    My TGA Pro audio shield has everything on board,...

    My TGA Pro audio shield has everything on board, ready to go, no soldering needed. Properly designed power and layout to isolate the analog from the digital stuff as much as possible. It recently...
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    You must have a ground between the boards...

    You must have a ground between the boards otherwise they won't be able to communicated with each other. Even if you cut the ground in the cable, they'll find a ground between them somehow, but it...
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    The link to the JAVA source code implementation...

    The link to the JAVA source code implementation is here.

    The rotation applied to the phaser in the paper is given as

    -i * (b-ma) * p * 2*PI / (m * O * N)

    The correct phase shift is


    //...
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    The paper published by the Ocean authors had a...

    The paper published by the Ocean authors had a typo in the phase calculation. The correct phase adjustment and demodulation function can be obtained from their public JAVA code of the algorithm, in...
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    Actually, now that I look closer, it's not the...

    Actually, now that I look closer, it's not the DMAMEM attribute that seems to make it work. Putting them in static memory works too. It's just the heap memory that doesn't work. So I guess the...
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    Well after weeks messing with the DMA I'm ready...

    Well after weeks messing with the DMA I'm ready to pull my hair out. I was able to get it to work with T4 only by declaring the buffers as DMAMEM instead of allocating off the heap. I tried using the...
  41. 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,...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  50. 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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