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  1. Just came across this. Reminds me of the...

    Just came across this. Reminds me of the mechanized feeding machine in Charlie Chaplin's "Modern Times", only
    rather better behaved!
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    You can just ask the compiler, using sizeof(). ...

    You can just ask the compiler, using sizeof().


    void setup ()
    {
    Serial.begin (...) ;
    Serial.printf ("char is %d bytes\n", sizeof(char)) ;
    ... etc etc
    }
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    You need an audio analyser, not a 'scope, to...

    You need an audio analyser, not a 'scope, to measure an audio system - 'scopes are mainly 8 bit resolution
    with high noise floors and so-so linearity (the front end typically has to work from DC to...
  4. Have you tried changing AUDIO_SAMPLE_RATE_EXACT...

    Have you tried changing AUDIO_SAMPLE_RATE_EXACT in AudioStream.h to 7.68e5 ?

    You might be able to sample that way (don't know though) - however you can't simultaneously handle 768
    and 48kSPS at...
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    Well for starters the key needs to be set once...

    Well for starters the key needs to be set once only, but I don't think that's your problem - with encryption
    code you have to make zero errors in the code otherwise the result is inpenetrable...
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    There's a whole thread about playback speed,...

    There's a whole thread about playback speed, probably worth a look: https://forum.pjrc.com/threads/63212-Pitch-control-of-sample-playback-current-state-of-things
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    You should do this anyway I think, since any such...

    You should do this anyway I think, since any such constants should have been defined in terms of AUDIO_BLOCK_SAMPLES
    from the get-go?
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    If you know the signal is only a 40kHz signal you...

    If you know the signal is only a 40kHz signal you dont need to sample that fast - you can simply compensate for the
    aliasing.

    Perhaps the signal isn't really a pure tone at exactly 40kHz, but is...
  9. Thread: Support

    by MarkT
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    Certainly sounds like the button is shorting the...

    Certainly sounds like the button is shorting the supply - the host computer is monitoring the USB power and detecting this.
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    Its all too common for MISO not to be connected...

    Its all too common for MISO not to be connected on cheap displays - and its annoying as most if not all COGs allow pixel values to be read
    back from the frame buffer, so omitting it reduces the...
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    I totally disagree, C is a low level language and...

    I totally disagree, C is a low level language and even the best programmers shoot themselves in the foot with
    it sometimes, life is too short to use such a rough edged tool for general purpose...
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    Both these things happen already as the static...

    Both these things happen already as the static initialization proceeds AFAICT. Disabling interrupts is absolutely essential to prevent
    the datastructures being corrupted during the connection...
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    It's in AudioStream.h, in cores/teensyX: For...

    It's in AudioStream.h, in cores/teensyX:

    For instance: https://github.com/PaulStoffregen/cores/tree/master/teensy4
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    Different tools for different purposes - C is not...

    Different tools for different purposes - C is not suited for programming in the large or for high-level coding.
    The lack of array-bounds checking in C and C++ is partly responsible for the huge...
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    SPI is for short distances only, same PCB or a...

    SPI is for short distances only, same PCB or a nearby module. Thus there's no connector standard for it.
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    From what I've seen of the codebase (T4 only) it...

    From what I've seen of the codebase (T4 only) it might work to use new and delete, I've not tried myself. I suspect
    there's been little testing so some things may work, others not... On the T4 the...
  17. Input protection diodes only apply to inputs! ...

    Input protection diodes only apply to inputs!

    For an output you need to avoid cooking the pad driver FETs by sticking to the max output
    current specification. For complex chips with lots of GPIO...
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    I suspect a heat gun is not going to be a good...

    I suspect a heat gun is not going to be a good experience, you need accurate temperature control and
    low airflow speed, or all the little parts are blown off the board.

    Hot air rework stations...
  19. Probably to clear the instruction pipeline while...

    Probably to clear the instruction pipeline while the clocks are stabilizing?
  20. You've read the forum rule ?

    You've read the forum rule ?
  21. Yes, its simple, you must prevent currents larger...

    Yes, its simple, you must prevent currents larger than IIC flowing in the protection diodes, either by a limiting resistor
    or other means (like schottkys). The restriction is only < -0.3V. The pin...
  22. The cables are insulated, they can rest on the...

    The cables are insulated, they can rest on the ground happily, seeing absolutely nothing from the static as they are shielded and insulated.

    The problem from static would be if someone walks...
  23. I would hope cli() and sei() clear and set the...

    I would hope cli() and sei() clear and set the global flag, which doesn't affect interrupt state,
    merely defers handling. From what I gather with ARM interrupts there's a register for deferring...
  24. The USB power comes from the RPi?

    The USB power comes from the RPi?
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    Are you trying to do half-duplex on a single...

    Are you trying to do half-duplex on a single wire, as opposed to full duplex using two signals, each uni-directional?
  26. The problem with ambient noises is they are very...

    The problem with ambient noises is they are very directional, and the human auditory system does a very good job of
    isolating each noise spatially (two ears). A single small microphone will not do...
  27. The headphone output is as I understand is not...

    The headphone output is as I understand is not ground referenced, ie HPVGND is a DC level that must
    not be connected to 0V ground (well not at DC for sure).
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    Yes, I reckon, but make sure the trace between...

    Yes, I reckon, but make sure the trace between the pin and cap isn't too skinny and runs over ground-plane
    to keep the inductance low.

    They are probably in the chip itself, I'd check the...
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    Really? You are allowed to populate the region...

    Really? You are allowed to populate the region of your pcb between the header rows, so you only lose those
    rows of connectors, and if you use surface-mount connectors you only lose pcb area on one...
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    In that case I'd suggest rather than editing...

    In that case I'd suggest rather than editing AudioStream.h, just touch it before compiling if you have overridden the sample
    rate - that way the sources to the library aren't changed, just the...
  31. Nice! Is the audio handled?

    Nice! Is the audio handled?
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    6 foot run is too long for reliable single-ended...

    6 foot run is too long for reliable single-ended fast logic signals. 6 inches is more normal :)

    You'd need to use something like RS485, LVDS, or an old fashioned line-driver / line-receiver pair...
  33. Second that - its a low-impedance stepper so...

    Second that - its a low-impedance stepper so requires current drive, DRV8825 modules and A4988 modules are the
    way to go, and you'll need to set to _0.35A_ max current setting for that motor. If...
  34. Thread: audio clock slip

    by MarkT
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    I don't know if you can still get bargains, but...

    I don't know if you can still get bargains, but you used to be able to pick up a used rubidium atomic clock module for
    $100 or so (typically these come from mobile phone base station upgrades).
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    I think you just have to #define the constant...

    I think you just have to #define the constant before #including AudioStream.h, as it doesn't override the define if already set.
  36. Thread: audio clock slip

    by MarkT
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    0.2ppm is the sort of accuracy you might see in a...

    0.2ppm is the sort of accuracy you might see in a brand new RF spectrum analyzer!

    Perhaps this is the future and will finesse the issue:...
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    Breakout boards with an I2S DAC on them do...

    Breakout boards with an I2S DAC on them do exist...
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    Should be fine. An LED + resistor is a load, not...

    Should be fine. An LED + resistor is a load, not a short circuit, so it won't overcome ground which will be 0V
    whatever. I'd double check there's no internal connections with a multimeter though -...
  39. The problem with that would be the Teensy isn't...

    The problem with that would be the Teensy isn't able to switch the optocoupler through the resistors...
    Open drain is the acknowledged way to do something like this, its often used for chip reset...
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    For the popping are you sure the audio stream to...

    For the popping are you sure the audio stream to the SGTL is getting all zeroes when you change volume? If so and the
    RH channel is popping that's the chip itself, not a discontinuity in data. Not...
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    You clearly haven't checked this in the source...

    You clearly haven't checked this in the source code - I'd recommend getting upto speed with the Audio lib internals
    to gain a deeper understanding of what goes on, AudioStream.h & AudioStream.cpp...
  42. Simple reversal is by definition not realtime. ...

    Simple reversal is by definition not realtime. You could process short samples and reverse each one, but
    then you have to have a delay. You also have to have some algorithm for breaking the...
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    Not sure what you are asking.

    Not sure what you are asking.
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    I suspect there's a uint16_t method for println. ...

    I suspect there's a uint16_t method for println. Note that int16_t and int32_t will not implicitly cast
    to unsigned types as negative values cannot be represented.
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    Are you talking to the display (ie using SPI bus)...

    Are you talking to the display (ie using SPI bus) when the high pitched noise is audible? Or could it be
    the PWM for the LED backlight?

    The pops will be a DC offset on the right hand channel I...
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    You aren't getting 32 bits, its just that println...

    You aren't getting 32 bits, its just that println only has a method for int, not int16_t, so the value is implicitly converted from
    16 bit to 32 bit (the natural size of int) by the compiler so it...
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    Actually its complex (maths joke...)

    Actually its complex (maths joke...)
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    Then you need to have your frequency variable i,...

    Then you need to have your frequency variable i, and cos and sin to convert that into position on the unit circle,
    all that remains is to evaluate that z value for all the poles and zeroes,...
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    You may be able to work in-place if using...

    You may be able to work in-place if using receiveWritable() and the endianness is correct for the algorithm,
    if copying out and back you simply copy back into the writeable audio block for each...
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    Filter responses are calculated from the poles...

    Filter responses are calculated from the poles and zeroes of the filter. Are we talking about
    analog filters or digital?
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