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  1. No. That would pull the opamp input to the rail....

    No. That would pull the opamp input to the rail. Capacitor is _across_ the lower resistor to short out noise voltage.
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    For something like this I'd always check with a...

    For something like this I'd always check with a multimeter and 1k resistor whether the LED already has current limiting
    resistor and double check the pin out and polarity (I usually do this for any...
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    There are many different chips in TFT screens -...

    There are many different chips in TFT screens - it really helps if you know which one yours has.
    I can't even see a make given for those boards.
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    You might want some RF filtering on the input and...

    You might want some RF filtering on the input and a resistor on the opamp output so it can drive long cables without
    the risk of oscillation. 1k series 470pF shunt for the input perhaps, and 100...
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    They are just alternative waveforms you select....

    They are just alternative waveforms you select. I'll look at index.html

    The issues that hold me back are:
    1) is it rock solid and tested
    2) does it have too much overhead (memory) to go into...
  6. Whoops! I had a look through the other...

    Whoops! I had a look through the other effects/synth classes for other mistakes like this and couldn't find any
    (I didn't do the inputs and outputs as they are quite complex with DMA and have no...
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    100k is rather high for a pot, which increases...

    100k is rather high for a pot, which increases sensitivity to noise pickup and may allow some crosstalk in
    the ADC. 10k linear is the go-to value for control pots, and often less than this for...
  8. A couple of things - adding a resistor of a...

    A couple of things -

    adding a resistor of a few k between the opamp output and Teensy pin will protect the teensy pin should it
    not be powered up when the opamp is.

    The virtual ground circuit...
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    I suggest testing the pull request branch and...

    I suggest testing the pull request branch and then feeback here and to the pull request comments. The changes are only on the teensy4 tree
    anyway, I don't know what the procedure is for merging...
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    No, certainly don't use the headphone jack. Its...

    No, certainly don't use the headphone jack. Its not ground-referenced and the sound quality is lower than the line-outs.

    The line-out pads are what you use to send to an amplifier.
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    I'd advise building the system up bit by bit, so...

    I'd advise building the system up bit by bit, so that its easier to diagnose the problems - or adding a debug mixer on
    the output that you can temporarily route a node in the graph to to check its...
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    This typically applies when the power amplifier...

    This typically applies when the power amplifier itself is clipping - in this case the DC offset can be
    substantial due to non-symmetric nature of the clipping (very much depends on the amp's...
  13. I think this is because otherwise you've got an...

    I think this is because otherwise you've got an audio stream component that's never been connected, so the program
    crashes on a null pointer when its update() is called on it - could be wrong, its...
  14. Thread: vtable problem

    by MarkT
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    Can't reproduce this - can you provide the...

    Can't reproduce this - can you provide the details needed to compile this - software version, teensy model, etc.
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    You need to check the mode is correct - that...

    You need to check the mode is correct - that means reading the timing diagrams in the datasheet
    usually as they don't like to make it easy for some reason. SPI has 4 modes and they are all...
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    SPI library docs?

    SPI library docs?
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    "volatile unsigned long" please - its confusing...

    "volatile unsigned long" please - its confusing to mix up qualifiers with the type like that. Qualifiers, then the type, is
    the norm and compatible with using typedef too :)
  18. If you directly connect AC or a negative voltage...

    If you directly connect AC or a negative voltage to any pin on any CMOS chip, you'll risk blowing it up
    if the signal goes below about -0.5V. Never do this.

    A good protection circuit on an...
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    You want about 50ms delay, try...

    You want about 50ms delay, try 8*AUDIO_BLOCK_SAMPLES

    With 2 blocks worth of delay that's about the same delay as speaker multipath in a standard room, so
    its probably just going to acoustically...
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    The T4 default SPI speed is way faster than most...

    The T4 default SPI speed is way faster than most Arduinos. The AS5047 has a max SPI rate of 10MHz...
  21. Not sure, think it was only on mic, could be...

    Not sure, think it was only on mic, could be something nearby in the electronic environment I suppose.
  22. Sounds amazing too - worth the headphones for...

    Sounds amazing too - worth the headphones for this one, not laptop speakers! Nice work.
  23. Not sure I have a photo - that was from an FFT...

    Not sure I have a photo - that was from an FFT direct to a TFT display on the Teensy. It was from when I was playing with
    coding higher resolution FFT than the audio lib ones and writing this to a...
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    I certainly would never trust any chip bought...

    I certainly would never trust any chip bought from eBay these days in the slightest unless I knew
    the reputation of the seller.

    I looked at the spectrum of the signals and the "distorted" one had...
  25. I would say its absolutely essential to add...

    I would say its absolutely essential to add protection if connecting direct to an external piece of equipment - most signal generators
    are capable of +/-15V or so, and modern ones without a physical...
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    Its very unusual to interfere with FM when its...

    Its very unusual to interfere with FM when its tuned to a station. Spurs can often be detected between stations though.
    My suspicion is you are tuned to a harmonic of some clock signal by chance.
    ...
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    If its distortion rather than noise, its not...

    If its distortion rather than noise, its not noise and we've been chasing our tails a bit!

    Have you seen this thread? https://forum.pjrc.com/threads/29284-Dual-channel-16bit-dac-PT8211/page3
  28. If you are trying to use a dynamic microphone...

    If you are trying to use a dynamic microphone then a series capacitor on the input is going to
    achieve this easily, say 10k to ground and 470nF series capacitor.

    I would have suggested removing...
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    I'd treat the Vdd on the PT8211 as an analog...

    I'd treat the Vdd on the PT8211 as an analog supply, use a separate supply for it from the digital ones (perhaps a 3.3V LDO regulator
    from the 5V?). At the very least it needs the filtering circuit...
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    Such as a separate Vdd from the Teensy?

    Such as a separate Vdd from the Teensy?
  31. This might be a possible cause: Incoming blocks...

    This might be a possible cause:
    Incoming blocks can be NULL, you should deal with this gracefully. Especially at start up before there's any AudioMemory allocated,
    then there are no blocks at all....
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    + isn't defined on c strings. the String class...

    + isn't defined on c strings. the String class can support that, not bare strings as concatenation
    involves memory management.

    You probably mean:


    const static char* INITPATCH =...
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    I got bored and had a go at doing this... ...

    I got bored and had a go at doing this...

    Created an AudioEffectWaveFolder class, here's the git hub links, but I've included at the end too.
    ...
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    effect waveshaper might be a possible approach,...

    effect waveshaper might be a possible approach, but I think this really needs a custom object to do the folding simply
    and efficiently.
  35. Can you set down your desired button behaviour as...

    Can you set down your desired button behaviour as a state-machine? That will make the coding straightforward as
    all the detail is in getting the state transitions as you want them - every part of...
  36. Search term "free windows DAW" perhaps? I...

    Search term "free windows DAW" perhaps? I immediately hit some reviews/comparisons from publications.
  37. Excellent - any issues I suggest report back to...

    Excellent - any issues I suggest report back to this thread.
  38. Thread: Oled i2c

    by MarkT
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    AVR microcontroller internal pullups are too weak...

    AVR microcontroller internal pullups are too weak for I2C (50k worst case), you definitely need pull up resistors for them too.
  39. There's a perhaps better approach to this - don't...

    There's a perhaps better approach to this - don't reset counts at all. Use it just like the output of millis() or micros() and
    subtract the previous value from the current value to determine how...
  40. You certainly don't need to build an amp from...

    You certainly don't need to build an amp from scratch, just snoop on the audio going into the active speaker as
    in your shortcut idea 1.

    FFT is an algorithm on an array of samples, how you...
  41. The sources aren't private, their open. ...

    The sources aren't private, their open. https://github.com/PaulStoffregen/Audio

    You can see the outstanding pull requests and changes, and the dates of last update for the files.

    And from the...
  42. I think you need to detect the button _changing_...

    I think you need to detect the button _changing_ state, not continually use its current state, and thus trigger the
    action when its pressed only.

    Then you simply need the state change code to set...
  43. What clock speed was that at? If at 600MHz...

    What clock speed was that at? If at 600MHz that's upto 2400 instruction issues (assuming dual issue fully utilized),
    That no longer appears particularly surprizing given there's no OS overhead to...
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    Just watch out for the high voltages if its using...

    Just watch out for the high voltages if its using a resonant transformer to drive the transducer, stick to the primary side!
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    You'd need an emulation layer for that, I think a...

    You'd need an emulation layer for that, I think a better approach is translate the code from direct port access
    back to digitalRead/digitalWrite calls, so its portable, then that should work on the...
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    Depends on the cutoff frequency desired and the...

    Depends on the cutoff frequency desired and the impedance. f = 1 / (2πRC), so
    C = f / (2πR)
  47. You know the T4 has hardware quadrature decoders...

    You know the T4 has hardware quadrature decoders built in and there's a library to use them?
    https://forum.pjrc.com/threads/58478-Teensy-4-x-H-W-Quadrature-Encoder-Library
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    A separate DDS module might be another approach -...

    A separate DDS module might be another approach - what do you want the 40kHz for? Pure tone or modulated?
    How accurate does the frequency need to be? What sort of jitter and noise is allowable?
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    KiCad is commonly recommended - I've not used it...

    KiCad is commonly recommended - I've not used it having started out with Eagle, but both are portable win/mac/linux AFAIK.

    You want auto-routing now, but having used these tools a while you'll...
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    The headphone output is floating above ground at...

    The headphone output is floating above ground at 1.56V or so deliberately so the chip doesn't need output capacitors
    nor a negative supply (the outputs are centred on 1.56V - measured with my Audio...
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