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  1. Replies
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    Use high value resistors in the divider so...

    Use high value resistors in the divider so current is limited? 100k or so ought to be benign. A few nF of capacitance might be
    needed to eliminate noise pickup, note.

    The sure-fire approach is...
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    Probably still has most of its capacitance -...

    Probably still has most of its capacitance - unless its actually shorted I'd leave it as is. These caps
    are a stack of parallel plates, losing some of the plates just reduces the capacitance. ...
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    There is some driving circuitry suggested for the...

    There is some driving circuitry suggested for the AD8885 ADC (high speed SAR 18 bit) in its datasheet,
    using an OPA350 opamps and 10 ohm resistors:
    https://www.ti.com/lit/ds/symlink/ads8885.pdf
    ...
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    Well for the T4 you'd be looking for a true...

    Well for the T4 you'd be looking for a true rail-to-rail input & output opamp capable of running at 3.3V supply,
    so that it can't damage the T4. Other than that nothing special for a low...
  5. You could use the same system, but have some...

    You could use the same system, but have some objects that treat the audio blocks as arrays of float
    rather than int16_t. You'd need two blocks per stream as sizeof(float) = 4 and sizeof(int16_t) =...
  6. If you connect a capacitor between mic and gnd...

    If you connect a capacitor between mic and gnd inputs, do you still get static?
  7. Arbitrary image rotation can be done without any...

    Arbitrary image rotation can be done without any trig, you decompose the rotation into 3 othogonal shear transforms
    and implement these shears directly on the pixel data, snapping to the nearest...
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    One capable of being powered from +/-12V, and...

    One capable of being powered from +/-12V, and which can swing to within 2V of the rails. Precision might be important
    since you'll have a gain of 17 or so, each 1mV of input offset translates to...
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    Yes, you can configure a AudioFilterBiquad as...

    Yes, you can configure a AudioFilterBiquad as three 1st-order sections for the 3 poles/zeros needed - you'd
    use setCoefficients explicitly.

    The RIAA curve has a lot of attenuation at high...
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    Have you tried calling the frequecy() method...

    Have you tried calling the frequecy() method after setup()?
  11. By output block you don't mean TDM output? It...

    By output block you don't mean TDM output? It would be possible to use 16 AudioRecordQueue objects (clearly not
    ideal for this situation, but certainly possible).

    The initializers for audio...
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    To understand digital PCB groundplanes, this is a...

    To understand digital PCB groundplanes, this is a good tutorial: https://www.maximintegrated.com/en/design/technical-documents/tutorials/5/5450.html
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    I wouldn't have expected a PNP to be useful for...

    I wouldn't have expected a PNP to be useful for level conversion to a higher voltage - NPN common-emitter inverter
    circuit is what's used - in other words low-side switching. Since BJTs turn on at...
  14. On the contrary a 4k7 pullup is standard for...

    On the contrary a 4k7 pullup is standard for OneWire devices. Parasitic power mode also requires the 4k7 pullup and a FET hard pullup as
    well during the conversion phase. I've used 20 DS18B20 's...
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    Normally you'd keep OE asserted, the LE is what...

    Normally you'd keep OE asserted, the LE is what clocks the data onto the latches. in normal mode
    shifting happens on every rising clock edge, and the shift register state is only copied to the...
  16. Its because its 2-times oversampled.

    Its because its 2-times oversampled.
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    I can't see the circuit being discussed... ...

    I can't see the circuit being discussed... Different opamps have different decoupling requirements, so
    which opamp?
  18. You are returning a pointer to a local array from...

    You are returning a pointer to a local array from inside the function via the path pointer. This is undefined, the storage for
    ldNumber is reclaimed when getLogicalDeviceNumber returns.

    I think...
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    Use schottky diodes to the (analog) rails with a...

    Use schottky diodes to the (analog) rails with a 1k series resistor in front - that will protect the CMOS protection diodes
    already inside the SGTL5000 chip (standard practice for externally...
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    You upload the wrong sketch which sets that pin...

    You upload the wrong sketch which sets that pin as an output for instance?
  21. 3.3V logic signals like SCLK/MOSI/MISO/#CS will...

    3.3V logic signals like SCLK/MOSI/MISO/#CS will be completely fine driven from any 3.3V microcontroller or any 3.3V CMOS logic family,
    logic signals are designed to interwork universally like this. ...
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    AFAICT by default the library uses interrupts (if...

    AFAICT by default the library uses interrupts (if you give it pins that support interrupts). If you look
    at the NoInterrupts example you'll see it explicitly prevents interrupts being used.
  23. Fine - although its pretty rare to damage a part...

    Fine - although its pretty rare to damage a part by overheating if you have the right equipment (ie temperature controlled).
    Its probably helpful if there's a lot of rework going on as it will be...
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    Not inside them, that's to create a critical...

    Not inside them, that's to create a critical section for communicating with the ISR from the
    rest of the program.

    You shouldn't be doing serial I/O inside an ISR, that could deadlock the...
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    Why are you disabling interrupts?

    Why are you disabling interrupts?
  26. Best not to inhale the solvent vapours then ;)

    Best not to inhale the solvent vapours then ;)
  27. Replies
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    If its not in the datasheet, I imagine you'd have...

    If its not in the datasheet, I imagine you'd have to measure this yourself. Typically separation decreases with increasing
    frequency, but it may not be a big issue at audio frequencies.

    The...
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    I'd reiterate the avoidance of pow(), which...

    I'd reiterate the avoidance of pow(), which returns double, as you shouldn't rely on exact floating point
    behaviour.

    You need to buzz out your circuit to check for shorts between adjacent pins I...
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    Have you tried WAVEFORM_BANDLIMIT_PULSE ? Takes...

    Have you tried WAVEFORM_BANDLIMIT_PULSE ? Takes more processing power but removes aliasing artifacts.
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    Yup, found an old HEF4051B, which I think is...

    Yup, found an old HEF4051B, which I think is equivalent to CD4051B, and the on-resistance rises rapidly below
    5V supply to about 2.5k or more at 3.3V. (Sample size of 1 pin on 1 chip, note). The...
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    The more I think about it the less I like the...

    The more I think about it the less I like the idea of the CD4051 at 3.3V supply - nowhere in the datasheet does it
    give any performance data for this low a voltage, and the on-resistance for 5V...
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    Pin 22 is sandwiched between the high speed I2S...

    Pin 22 is sandwiched between the high speed I2S clock pins so will pick up some capacitive coupling - as the pots have their
    wipers held at low impedance by those caps I suspect the issue is stray...
  33. First step is get a metal enclosure or wrap you...

    First step is get a metal enclosure or wrap you existing enclosure in something conductive, and ensure your wiring is all shielded.

    http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
    ...
  34. Very nicely put together!

    Very nicely put together!
  35. Rather than '' or 'boo' which could actually be...

    Rather than '' or 'boo' which could actually be handy in some circumstances. High level languages with exception
    handling normally fix all these awkward corners by throwing an exception.
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    Yes, consider a square wave. It's spectrum...

    Yes, consider a square wave. It's spectrum technically goes on forever, all the odd harmonics (in practice
    the first few 1000 are easily powerful enough to be audible if in the range of hearing). ...
  37. I submitted a bug to the Arduino bug report...

    I submitted a bug to the Arduino bug report system about this, WString seems to have been in error like
    this for a while, but no-one noticed as most microcontrollers let you deference NULL without...
  38. Perhaps: void String::move(String &rhs) {...

    Perhaps:


    void String::move(String &rhs)
    {
    if (buffer) {
    if (capacity >= rhs.len) {
    if (rhs.buffer)
    strcpy(buffer, rhs.buffer);
    else
  39. I can confirm this - but it doesn't happen on the...

    I can confirm this - but it doesn't happen on the T3.2 despite the printing and String
    code seeming identical where it should matter.
  40. You do realize that the chip has a high speed...

    You do realize that the chip has a high speed FPU, and clocks at 600MHz? CMOS power consumption goes as

    N x f x C x V^2 where N represents the number of clocked gates (complexity), f the clock...
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    We definitely need to see your circuit to...

    We definitely need to see your circuit to investigate further.
  42. No, I very much doubt an optical mouse is...

    No, I very much doubt an optical mouse is anything like fast enough as it has to do computation on the chip
    to correlate optical image movement - and the optical image is supposed to be focussed on...
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    A separate 3.3V regulator will be needed for the...

    A separate 3.3V regulator will be needed for the LED circuit - the T4.1 has more devices on it that
    use power than the T4.0, so less is available for off-board use. One of the compromizes on a...
  44. Shielding for everything in a high-noise...

    Shielding for everything in a high-noise environment is a given - in fact there's rarely an excuse not
    to shield enclosures and cables...

    Good decoupling for supply rails can prevent transients...
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    To look inside applications on MacOS using the...

    To look inside applications on MacOS using the finder try right-click "show package contents" to see the internals.

    Then its Contents/Java/hardware/......
  46. I think I erroneously assumed from "recorded"...

    I think I erroneously assumed from "recorded" that this was audio (been doing a lot of this recently) -
    if this a data-logger style application then the 1/f noise knee would be more important than...
  47. Yes, SDcards get hot, they dissipate a lot of...

    Yes, SDcards get hot, they dissipate a lot of power for a small device. [ especially when writing them ]
  48. My observations on this circuit. Firstly the...

    My observations on this circuit.

    Firstly the AD8225 and OP2177 aren't rail-to-rail, which can be very limiting operating from a single 5V.
    Have a look at devices like the OPA1692 or AD8586 for...
  49. I annotated my T4.0 pin-out card with dots on...

    I annotated my T4.0 pin-out card with dots on each of the pins used by the AudioShield
    so I don't have to keep pulling up the schematic of the shield. Might be a useful addition to
    the cards in...
  50. Input_Start needs to be declared volatile.

    Input_Start needs to be declared volatile.
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