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    Yes, the T4 processor cannot tolerate 5V at all,...

    Yes, the T4 processor cannot tolerate 5V at all, you have to be super careful if any 5V signals are around. Its always worth buzzing out a circuit before powering up for supply shorts and stuff life...
  2. For a clock you'd probably need the...

    For a clock you'd probably need the battery-backup facility of a RTC chip/module anyhow so you'd pick one of those with the desired accuracy in practice

    It's pretty common for microontroller based...
  3. BTW I use the Python module scipy.signal, it does...

    BTW I use the Python module scipy.signal, it does a similar job to MATLAB for these filtering calculations, all open source and free. https://docs.scipy.org/doc/scipy/reference/signal.html
  4. For large FIR filters one approach is to use...

    For large FIR filters one approach is to use uniformly partitioned convolution, which allows FFT to do the heavy lifting and the partitioning allows close to real-time response, depending on the size...
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    Fresh flux is a reasonably good insulator, the...

    Fresh flux is a reasonably good insulator, the problem is as it ages it can oxidize, blacken and become conductive, and it can be very slightly conductive due to moisture (not usually a problem for...
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    Use an array of pointers or references to the...

    Use an array of pointers or references to the stepper objects, or else define the steppers as an array in the first place (there is some C++ syntax for initializing an array of objects with their...
  7. You need separate grounds for power and signals. ...

    You need separate grounds for power and signals. Power grounds carry high currents and for motors like this very high dI/dt values, which means a great amount of noise voltage across the ground...
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    I've always used around 18pF crystals and 18pF or...

    I've always used around 18pF crystals and 18pF or 22pF load caps on ATmega's without issue. I believe its not super critical. Note the load caps are effectively in series from the crystal's...
  9. The datasheet for the SGTL5000 suggests it uses...

    The datasheet for the SGTL5000 suggests it uses upto about 6.5mA, its not an issue AFAICT.
  10. Processors generally produce a large amount of...

    Processors generally produce a large amount of digital noise into their supply rails, which is why its common to have separate analog and digital supplies and grounds. Another thing you have to...
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    And thinking some more it may be that most of the...

    And thinking some more it may be that most of the time in your interrupts is register dumping and restoring - can you make the ISR just write the value to the buffer and do nothing else, without...
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    One way to debug interrupts is use a digital pin...

    One way to debug interrupts is use a digital pin (with fast writes or low-level register manipulation) so you can monitor the entry/exit using a 'scope.
  13. With the loop that's not what I call 'empty', its...

    With the loop that's not what I call 'empty', its busy-looping, stealing the CPU until pre-emption occurs.
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    Some frequency to voltage converters might be one...

    Some frequency to voltage converters might be one approach, then you can use ADC inputs.
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    The FFT is not a panacea - this sounds more like...

    The FFT is not a panacea - this sounds more like a problem for correlation/convolution techniques. (Having said that you can use the FFT to implement fast correlation/convolution, even with...
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    I think you just have to hold off reporting...

    I think you just have to hold off reporting noteOff to the envelope till isSustain() returns true. The releaseNoteOn parameter may also have an effect on this behaviour.
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    Piezoelectric crystals are current sources...

    Piezoelectric crystals are current sources (strictly speaking charge sources), so you can just put a low value resistor across the output to reduce the output voltage. Without any load they drift a...
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    This might be that you are grounding the...

    This might be that you are grounding the _headphone_ output "ground" pin - you mustn't do this, its not at ground potential at all.

    If that's not the issue (the line ground pin should be OK), the...
  19. The step down regulator is likely the predominant...

    The step down regulator is likely the predominant source of the noise (I presume its a switch-mode converter). I suggest using a clean supply for the amplifier not shared with anything digital. ...
  20. Datasheet of the mems mic?

    Datasheet of the mems mic?
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    Most encoders are open-collector, so try changing...

    Most encoders are open-collector, so try changing


    pinMode(ChannelA_LEFT, INPUT);
    pinMode(ChannelB_LEFT, INPUT);
    pinMode(ChannelA_RIGHT, INPUT);
    pinMode(ChannelB_RIGHT, INPUT);

    to
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    You don't want sharp edges with a graphic...

    You don't want sharp edges with a graphic equalizer normally, you want smooth transitions. The Q of the individual stages needs to match their geometric spacing. Sounds like you have one control...
  23. Well it appears to be a variable low pass filter...

    Well it appears to be a variable low pass filter and a power amp output. The LM386 hasn't been made for years, doubt you'll find one that's not a fake, perhaps a small class-D chip would be a...
  24. The fast I2S signals (especially MCLK) might not...

    The fast I2S signals (especially MCLK) might not be reliable with long jumpers like this, especially with all that loop area - bundle them all together if you can to improve signal quality. A large...
  25. If you use only the full voltage from the battery...

    If you use only the full voltage from the battery and buck converter(s) you'll be able to change to a different power
    source flexibly, as well as not unbalancing the cells.
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    Stencils are designed to be stretched taut in a...

    Stencils are designed to be stretched taut in a stencil frame, the fact the stainless came off a roll (which is why they
    have a curve) wouldn't normally cause issues used with a frame (might make...
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    Perhaps a link to the datasheet for the parts in...

    Perhaps a link to the datasheet for the parts in question? - better than trying to guess what "high definition"
    might mean to you, 1000 PPR, 10000 PPR, or even more?

    How many encoders are likely...
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    What are you interfacing to that needs so many...

    What are you interfacing to that needs so many interrupt inputs?
  29. Python3 bytestrings are not the same as unicode...

    Python3 bytestrings are not the same as unicode strings (Python3 strings are unicode). A bytestring is notated b'xxxxxxxx'
    Python3 strings can be interconverted <-> bytestrings if you give the...
  30. IIR isn't used for oversampling normally due to...

    IIR isn't used for oversampling normally due to the phase error, and the fact polyphase FIR filters can be _much_ faster.
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    ILI9341 is a chip, not the actual TFT display. ...

    ILI9341 is a chip, not the actual TFT display. This sort of thing is why you should try to find something with a decent datasheet.

    I'm sure there's a lot of difference between different displays....
  32. What bit depth are you assuming? Why double...

    What bit depth are you assuming? Why double floats if only sampling 16 bits (the Audio lib is 16 bit)
  33. Thread: Mushroom Music

    by MarkT
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    No, those signals are way too small to be fed...

    No, those signals are way too small to be fed direct to the ADC and get anything meaningful out.

    An instrumentation amp is probably the way to go, though you'd need to ensure the potentials fall...
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    Forum rule? This is a software problem I think,...

    Forum rule? This is a software problem I think, the dropout is one audio block I suspect, ie 2.9ms, although
    your 'scope shots omit timebase info so that's a guess.
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    The pin probably has bus-hold enabled. See...

    The pin probably has bus-hold enabled.

    See this thread:
    https://forum.pjrc.com/threads/69671-Teensy-4-0-4-1-web-pages-need-a-warning-about-INPUT_DISABLE-on-Analog-Inputs?highlight=bus-keeper
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    Just to clarify, 400kHz. 2.5Ás clock cycle, not...

    Just to clarify, 400kHz. 2.5Ás clock cycle, not 2.5ns! 100kHz and 400kHz are the commonest I2C rates.
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    Clearly visible 7.68MHz xtal, so good!

    Clearly visible 7.68MHz xtal, so good!
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    Well you have the circuit... Can you post the...

    Well you have the circuit... Can you post the schematic? Is this a module? Does it have a xtal on it?
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    I second that - its essential for a sigma-delta...

    I second that - its essential for a sigma-delta chip like this has a good quartz-controlled clock - is it actually running at 7.68MHz?
  40. When begin_v2_b2() returns all the audio objects...

    When begin_v2_b2() returns all the audio objects have their destructors called and cease to exist. This won't be useful, and won't
    work at all because audio objects that do I/O set up DMA and...
  41. That's the point - the signal "bypasses" the...

    That's the point - the signal "bypasses" the diodes unless the input voltage strays out of range, in which case one of the diodes
    conducts and clamps the voltage.
  42. Two Schottky diodes and a Teensy (or any CMOS...

    Two Schottky diodes and a Teensy (or any CMOS logic chip at all). This is the standard voltage protection - for surface mount people
    generally use a dual Schottky in a SOT23 package for this.
    ...
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    To get precision timing the #SYNC line probably...

    To get precision timing the #SYNC line probably should be driven in hardware from, say, a PWM output set to the right speed.
    Then the code to read the data can be interrupt driven from #DRDY going...
  44. Zeners are not really the answer (they can have...

    Zeners are not really the answer (they can have pretty soft knees in their response too), the way to do this is with a pair
    of Schottky diodes to the rails and a series resistor:

    28183

    The...
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    I believe the range depends on which FFT window...

    I believe the range depends on which FFT window is used as they are not normalized for level IIRC.

    Perhaps connect a AudioSynthWaveformSine into AudioAnalyzeFFT1024 to find out? A full-scale...
  46. 20MHz is just about doable on a breadboard, but...

    20MHz is just about doable on a breadboard, but you must use good layout - short direct cut-to-length wires, form a ground-plane
    (well, ground-grid) using regularly spaced ground links. Decoupling...
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    Maybe use star-grounding for the various power...

    Maybe use star-grounding for the various power supplies? I see several loops in the ground including high-current paths, which isn't a
    great plan. Try to ensure any signal wire only runs alongside...
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    The audio shield socket does not have microphone...

    The audio shield socket does not have microphone connection, and is definitely intended for a TRS cable. If you need a microphone connection
    you'll need a splitter.

    Thinking about the SGTL5000...
  49. A 'scope allows you to check the signal integrity...

    A 'scope allows you to check the signal integrity on the bus - needs to be reasonable bandwidth for high speed logic, 100MHz+ really.
    This is the sort of problem a logic analyzer will not help with...
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    Do you have a TRS-TRS cable? Try that in the...

    Do you have a TRS-TRS cable? Try that in the first instance, shouldn't be any issues.
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