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  1. You could also add an inverting charge pump - the...

    You could also add an inverting charge pump - the AD8224 will run on 3.3V and -3.3V.
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    Now we need a PTP like protocol to exchange clock...

    Now we need a PTP like protocol to exchange clock rate information between hosts. Preferably one that is flexible about what the transport is. Serial, RF, ethernet, hardware pin, etc. Is there...
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    > no more sliding clocks now Just to be clear,...

    > no more sliding clocks now

    Just to be clear, your clocks are still sliding. But perhaps at such a low rate that you don't care.
  4. Your first graph has a scale that goes negative. ...

    Your first graph has a scale that goes negative. But in single ended mode, the output of the ADC is unsigned. Mix up signed and unsigned and you get strange jumps at 32767.
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    > allows 0%error for all std frequencies More...

    > allows 0%error for all std frequencies

    More precisely, 0% error from the source. But a crystal source always has error, so all you can ever do for the absolute rate is "close enough". Ie, a...
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    Sounds good. Change the clock setting code to...

    Sounds good. Change the clock setting code to use a large denominator and floating point. Then anyone wanting to tweak rate can a) change AUDIO_SAMPLE_RATE_EXACT at compile time or b) change...
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    I toggled CCM_ANALOG_PLL_AUDIO_NUM between 2240...

    I toggled CCM_ANALOG_PLL_AUDIO_NUM between 2240 and 2241 every second with no audible effect. This is with SPDIF output to an external DAC.

    For most use cases, only small changes are needed -...
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    Nice! Kudos for not trusting the manual. ...

    Nice! Kudos for not trusting the manual.

    Add something like PTP and you can get sync, even over wireless.
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    I see Frank's point. Not sure what I did wrong...

    I see Frank's point. Not sure what I did wrong when I tested it and got a better match between my PC and teensy rate. Perhaps a misleading random change in one of the clocks.

    Looks like it...
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    I suspect that your best bet is to use what you...

    I suspect that your best bet is to use what you have but add more buffering (to cover the gaps).
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    As Paul explains, the decimal portion of...

    As Paul explains, the decimal portion of AUDIO_SAMPLE_RATE_EXACT *is* used. On a T4, you can use it (at compile time) to get two asynchronous clocks to be close to the same rate. But clocks change...
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    You might be able to adapt the "flasher4" code to...

    You might be able to adapt the "flasher4" code to do this.

    https://forum.pjrc.com/threads/29607-Over-the-air-updates/
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    > We like to detect a clipped audio signal coming...

    > We like to detect a clipped audio signal coming from the mixer

    Remko wants to detect clipping that occurred in the mixer or upstream of it. The signal level is likely to be fine once it gets...
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    Another common problem is noise from ground...

    Another common problem is noise from ground loops. Don't reference to any noisy ground that you don't have to. Use outputs from an isolated teensy+audio adapter as balanced signals into...
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    Clipped signals produce more high frequency...

    Clipped signals produce more high frequency energy - which blows tweeters.

    The histogram method here sounds promising. Or do a FFT and compare 3khz and above energy to energy below 3khz.
    ...
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    It's easier if you make the Teensy/ESP a fixed ip...

    It's easier if you make the Teensy/ESP a fixed ip address web server on your wifi network and then have the PC poll it via http.
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    Do #1 - teensy headphone jack into mixer line...

    Do #1 - teensy headphone jack into mixer line input.
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    What is the feasibility of adding virtual files...

    What is the feasibility of adding virtual files to MTP? For example, "memory", which would provide read access to all memory in the teensy?
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    Any easy, standards based way for a PC to access...

    Any easy, standards based way for a PC to access non-volatile data (eeprom or other) in a teensy would be useful. Perhaps virtual files accessed via MTP?

    For example, I run audio convolution...
  20. Thread: i.MX RT1170 ??

    by jonr
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    The NXP i.MX RT1176 eval board should be more...

    The NXP i.MX RT1176 eval board should be more widely available in February.
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    Besides the clear need for more structure on top...

    Besides the clear need for more structure on top of teensy non-volatile storage, there is the barrier-to-change business issue. It should be easy to port software from ESP32 to teensy. The reverse...
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    Seems like such a library should be built on top...

    Seems like such a library should be built on top of teensy's EEPROM code. For many uses, far less than 64K is adequate.
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    This is worth reviewing: ...

    This is worth reviewing:

    https://arduino.stackexchange.com/questions/57645/trouble-configuring-arduino-due-spi-to-adc
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    > I need to acquire 200,00 samples to have a...

    > I need to acquire 200,00 samples to have a correct 100khz samplerate

    I'd word it as "the setting and library will cause the ADC to acquire 200,000 samples/sec to produce the correct output rate...
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    It tries to produce the derived sample rate that...

    It tries to produce the derived sample rate that you specified (100,000), no matter how much averaging you do. In your example, 200,000 samples/sec need to be taken which is then reduced to 100,000...
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    Did you try changing AUDIO_SAMPLE_RATE_EXACT as...

    Did you try changing AUDIO_SAMPLE_RATE_EXACT as suggested in #4?
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    Regarding clock rate sync between two...

    Regarding clock rate sync between two non-wired-together sources, just adding a GPS module to each one might be easier than implementing PTP.
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    I find the manual quite dense, but as I see it, a...

    I find the manual quite dense, but as I see it, a clock can be applied to the SPDIF_EXT_CLK pin and this can be used as the SPDIF clock, Then the SAIs can use the SPDIF clock as their clock (see...
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    > will that slow things down If you are...

    > will that slow things down

    If you are concerned about speed, then I encourage you to learn how to measure speed. Search this forum for "ARM_DWT_CYCCNT".
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    Other than using the hardware audio inputs (I2S,...

    Other than using the hardware audio inputs (I2S, spdif), I'm not aware of any way to get a teensy audio output to precisely sync with an asynchronous clock from another source. I think you could...
  31. The demo here sounds quite effective: ...

    The demo here sounds quite effective: https://www.seeedstudio.com/ReSpeaker-Mic-Array-v2-0.html

    On the other hand, if the source is at a fixed position, it would be interesting to hear how well a...
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    Try turning off interrupts with cli().

    Try turning off interrupts with cli().
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    Frequent overruns unless I patch the feedback...

    Frequent overruns unless I patch the feedback code in usb_audio.cpp.

    https://forum.pjrc.com/threads/61142-USB-Audio-Frame-Sync-on-Teensy-4-0
  34. Your plan is sound. I'd buy a toslink input...

    Your plan is sound. I'd buy a toslink input module and a relay module (to send the 12V amp on signal). Then it's just software.
  35. > The display then shows 1,178 to 1,182 V...

    > The display then shows 1,178 to 1,182 V (probably RMS).
    > My oscillator (AC coupling) shows me Ue = 352 mVpp / 123 mV RMS.

    I'll assume "oscilloscope". When a multimeter reads ~10x more than an...
  36. What does a multimeter read (at the input pin)...

    What does a multimeter read (at the input pin) for both AC and DC?
  37. What do you get with DC voltages?

    What do you get with DC voltages?
  38. Thread: TDM as slave

    by jonr
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    So you want a T4 to produce 2 TDM outputs that...

    So you want a T4 to produce 2 TDM outputs that are precisely time synchronized with each other. I don't know much about it, but will give my thoughts anyway. 6.15 us is a long time for a T4. If...
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    It's time to start putting parts on the bottom...

    It's time to start putting parts on the bottom side.
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    Typically more like this: ...

    Typically more like this:

    arm_rfft_fast_instance_f32 S;
    arm_rfft_fast_init_f32(&S, 32);

    Be careful, as I recall, the real fft had a funky format for the results.
  41. A slightly related thing I came up with. At...

    A slightly related thing I came up with. At first the "case function" doesn't look legal.


    constexpr unsigned hash(const char *string)
    {
    return *string == 0 ? 17325 : *string + (*string *...
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    Try using "unsigned volatile long" so the...

    Try using "unsigned volatile long" so the compiler doesn't optimize away your loop.
  43. Thread: TDM as slave

    by jonr
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    What do you mean by "not in sync"? What problem...

    What do you mean by "not in sync"? What problem does it cause? Input or output?
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    I use USB input and toslink output. Combined...

    I use USB input and toslink output. Combined with a high quality DAC, I have no noise.
  45. > utilize more IO (10 or so) pins of the chip ...

    > utilize more IO (10 or so) pins of the chip

    What kind of IO do you need? Digital input, output, analog? How fast?

    For example, a "PCF8575 IO Expander Module I2C To 16IO" might work at far...
  46. A few K resistor is often helpful for protecting...

    A few K resistor is often helpful for protecting inputs.
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    Define "noise free". IMO, the teensy4 ADC is...

    Define "noise free". IMO, the teensy4 ADC is pretty noisy. Oversampling + trimmed mean will help some.
  48. Your Master code doesn't even compile. Probably...

    Your Master code doesn't even compile. Probably better not to use SoftwareSerial. And think through timing issues.
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    Confirmed on Teensyduino 1.54 Beta #4. Some...

    Confirmed on Teensyduino 1.54 Beta #4. Some overruns/glitches with the stock code, none with the above changes. Using Linux Mint 19.1 with pulseaudio and a usb card that is about 200 ppm off from...
  50. Serial is probably best.

    Serial is probably best.
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