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  1. Replies
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    The MCP23017 datasheet says it supports 100kHz,...

    The MCP23017 datasheet says it supports 100kHz, 400kHz and 1.7MHz I2C, and has a section on timing requirements for each mode - that
    probably explains why 1MHz is problematic.
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    The Teensy 4 chip isn't rated for more than a few...

    The Teensy 4 chip isn't rated for more than a few mA per pin, I think you are just overloading it.

    However I've had a look at the Vishay datasheet for the 6N137 - you should be feeding it between...
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    24 bit filter coefficients, or 24 bit bit audio...

    24 bit filter coefficients, or 24 bit bit audio or both?
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    Its called MIDI because you just named it as...

    Its called MIDI because you just named it as such. MIDI_CREATE_INSTANCE is a macro that defines an instance
    with the name you give it (last argument to the macro).
  5. pdm input and i2s output ? Have you seen the...

    pdm input and i2s output ? Have you seen the audio lib design tool: https://www.pjrc.com/teensy/gui/
  6. If you are lucky the current was limited enough...

    If you are lucky the current was limited enough not to damage the protection diodes on the chip. 10k is
    a fairly large value and limits the current to 1.7/10k = 170uA.
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    Definitely rather noisy, dynamic mics are low...

    Definitely rather noisy, dynamic mics are low impedance and a good mic preamp is needed to get a good
    noise figure - otherwise there's little point moving to a professional microphone in the first...
  8. 34 and 35 are on the unpopulated microSD pads...

    34 and 35 are on the unpopulated microSD pads (light blue section - they are silk-screened with the light blue names).
    MISO1 is not brought out AFAICT - not every pin can be brought out on the T4.0
  9. There should be a definite noise reduction if...

    There should be a definite noise reduction if using a separate, linearly regulated, analog supply on any ADC or DAC for audio -
    digital supplies for a high speed CPU are typically attrociously noisy...
  10. Just have the pinout cards to hand, like I have! ...

    Just have the pinout cards to hand, like I have! Glad its flying now..
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    You will be seeing the battery voltage droop...

    You will be seeing the battery voltage droop under load - SDcards are very spiky loads as the internal erase cycles are
    heavy current users (there's a whole boost converter being run on the silicon...
  12. [ BTW I think what you have isn't technically a...

    [ BTW I think what you have isn't technically a network analyzer, as you are not measuring reflected power(?) - what you have is
    equivalent to a spectrum analyzer with tracking generator, only...
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    Set pin SS as an output - the Teensy SPI lib...

    Set pin SS as an output - the Teensy SPI lib doesn't do this for you. Look under "Basic Usage" here:
    https://www.pjrc.com/teensy/td_libs_SPI.html
  14. Pins 7 & 8 on the T4 are RX2/TX2, and are also...

    Pins 7 & 8 on the T4 are RX2/TX2, and are also I2S pins. Are you using either of these? On the T3.2
    RX2/TX2 are on different pins...
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    The way "thru" works in such devices is using...

    The way "thru" works in such devices is using software I think, since the use of the output port has to be shared
    between local output packets and "thru" packets without mangling either. I think...
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    BJTs are typically slower than MOSFETs if the...

    BJTs are typically slower than MOSFETs if the MOSFET is driven with enough current - however a
    large MOSFET can have a lot of capacitance and need quite high currents to switch fast - so it
    very...
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    If you do some testing you'll find they are...

    If you do some testing you'll find they are simply not reliable enough, fortunately, as a ceiling fire in a public space is about the
    worst-case scenario there is - you do not want to go there,...
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    Then you have no headroom for a regulator. I'd...

    Then you have no headroom for a regulator. I'd suggest separate supplies for Teensy and amp in that case.
    Digital and analog audio don't mix well as even a few mV of digital hash can be highly...
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    A low drop out linear regulator capable of the...

    A low drop out linear regulator capable of the current and with a suitable voltage. There are 1000's - I am not a search engine!
    Digikey/Mouser/Farnel - they have search facilities.... What battery...
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    As I said use a separate linear regulator for a...

    As I said use a separate linear regulator for a quiet supply - this means you need enough voltage headroom in the first place.

    You may still have the issue that the source isn't clean - do you...
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    Ah, the TDA2822 has only 24--30dB of PSRR, so it...

    Ah, the TDA2822 has only 24--30dB of PSRR, so it definitely needs a linear voltage regulator all to itself to be "quiet"...
    Even the PAM8403 class D chip does a lot better than that (59dB PSRR)
  22. The FFT utilizes a factorization of the DFT...

    The FFT utilizes a factorization of the DFT matrix and divide-and-conquer to calculate the DFT more efficiently,
    its just algebraic simplification at heart.
    Its common, but not necessary, to...
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    I can't see a reference design - the datasheet...

    I can't see a reference design - the datasheet does explain about noise-reducing components on the digital signals,
    but you seem to have used 100nF for a noise-reducing capacitor value which is far...
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    Can't find a datasheet for the TDA1822 - is that...

    Can't find a datasheet for the TDA1822 - is that the correct part number? what sort of amp is it?
  25. In the arm_cfft_radix4_q16 call, part of the...

    In the arm_cfft_radix4_q16 call, part of the CMSIS library provided by ARM:


    arm_cfft_radix4_q15(&fft_inst, buffer);

    You can look up the docs for these arm routines by googling the function...
  26. Or is shorted, or lacks proper pull-up resistor -...

    Or is shorted, or lacks proper pull-up resistor - I suggest using a multimeter and turning the encoder very slowly to check the
    voltages are changing as expected on either signal.
  27. That's odd as processor usage should be...

    That's odd as processor usage should be independent of memory use really?!
  28. Thread: ADXL mm/s

    by MarkT
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    First an accelerometer gives acceleration...

    First an accelerometer gives acceleration readings, m/s^2, not m/s

    Secondly magnitude _is_ amplitude (without the phase).

    To calculate totals you have to add magnitude-squared, which is...
  29. Ditto AudioProcessorUsage and...

    Ditto AudioProcessorUsage and AudioProcessorUsageMax() then. If the processing is taking 100% of the CPU, same
    problem...
  30. The problem is that buffer is actively...

    The problem is that buffer is actively overwritten everytime there's enough new samples, so you can't
    guarantee to read a consistent set of frequency data without taking a snapshot like the code...
  31. Are you using physical pull-ups on the encoder...

    Are you using physical pull-ups on the encoder lines? internal pullups are weak and wouldn't usually be enough
    for a signal that goes off some distance in a cable run. 4k7 is a good general value...
  32. Have you used AudioMemoryUsage() and...

    Have you used AudioMemoryUsage() and AudioMemoryUsageMax()? You have a lot of objects, 20 blocks sounds stingy to me.

    You are perhaps hearing every other block being missing due to an inadequate...
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    The IM69D130 has an acoustic overload point of...

    The IM69D130 has an acoustic overload point of 130dB (hence the 130 in the part number??). Thus for normal levels around 60--70dB you'd
    expect it to be 60-70dB down from full-scale, suggesting an...
  34. It doesn't currently return complex values. It...

    It doesn't currently return complex values. It wouldn't be hard to create a version that produced complex though.

    The code uses dual 16 bit operations on the two halves of the complex value for...
  35. Thread: Gate

    by MarkT
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    I think I'd prefer AudioEffectNoiseGate so its...

    I think I'd prefer AudioEffectNoiseGate so its clear what sort of gate it is (for instance CV/gate interface is a thing in modular synthesis).
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    Not a great idea to have long wires with fast...

    Not a great idea to have long wires with fast logic signals - if you have to run longer
    cables, twist each logic signal with a ground wire return to reduce high-speed crosstalk perhaps?
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    Stuff's in...

    Stuff's in /Applications/Teensyduino.app/Contents/Java/hardware/teensy/ for me....
  38. Typical fast processors like the iMXRT1062 you...

    Typical fast processors like the iMXRT1062 you need to keep edges really fast - for instance unless the GPIO
    is set to hysteresis mode the datasheet says a max transition time of 25ns is required -...
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    see this thread:...

    see this thread: https://forum.pjrc.com/threads/46866-string-help

    Also posting an image of your code makes it impossible to copy and paste the code into an IDE window - few are going
    to help you...
  40. A slowly varying signal will also create multiple...

    A slowly varying signal will also create multiple transitions, logic inputs require fast edges for correct operation.
  41. By far the most likely explanation is the...

    By far the most likely explanation is the interrupt pin is changing multiple times. How are you driving the
    PIN_IN ? If by a mechanical switch or button you will see bouncing.

    use...
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    I thought I'd do a bit of proof-reading myself...

    I thought I'd do a bit of proof-reading myself and found this, also on the Audioshield page:
    Actually isn't 'sub-audible' referring to volume level, not pitch? Infrasonic perhaps?
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    Well I saw an Adafruit webpage about a motor...

    Well I saw an Adafruit webpage about a motor controller module talk about "active breaking" today, so maybe
    that's not so bad!
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    Did you read the part about having to have the...

    Did you read the part about having to have the Teensy plugged in? Its not clear from your account.
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    You probably need to firm up your notion of "some...

    You probably need to firm up your notion of "some sort of vision system" - this tends to suggest OpenCV on RPi is needed?
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    Note that on the faster Teensy's the AccelStepper...

    Note that on the faster Teensy's the AccelStepper generates pulses that are too short, unless you call setMinPulseWidth(10) or so.
  47. A few weeks/months ago there was a thread about...

    A few weeks/months ago there was a thread about someone having trouble with this library, you might
    want to hunt it down and see if you've addressed the issues from that thread, I suspect so.
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    Find a tutorial on DDS perhaps?

    Find a tutorial on DDS perhaps?
  49. No, higher bandwidth will help with narrow pulses...

    No, higher bandwidth will help with narrow pulses of course, but you should see something with that bandwidth even for pretty fast pulses.
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    The IM69D130 is a PDM microphone, not I2S.

    The IM69D130 is a PDM microphone, not I2S.
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