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  1. Its likely to be worth figuring out if some...

    Its likely to be worth figuring out if some clever mechanism can drastically reduce costs - 500 is 20 x 25 array or so.
    Any way to common up the mechanical drive to a whole row may be a winner - a...
  2. Clamping signal lines to the rails with Schottky...

    Clamping signal lines to the rails with Schottky diodes is standard really - for any logic signal going off-board.
    I've seen BAT54S and QSBT40's and similar used for this. Some series resistance...
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    I think the white silk-screened arrow indicates...

    I think the white silk-screened arrow indicates the wiper starts at the right hand pad for fully anticlockwise...
  4. An output low isn't a hard ground, might even be...

    An output low isn't a hard ground, might even be better due to the small output resistance reducing reflections,
    I can see that would make pinouts simpler.

    It allows for future expansion of...
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    Every relay coil must have a snubber diode -...

    Every relay coil must have a snubber diode - otherwise you risk blowing up a transistor. Can you share your
    circuit for the relay driving? Perhaps you have commoned up the relays in pairs? That...
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    No, because "resampler" is still an opaque black...

    No, because "resampler" is still an opaque black box. I'd just like a map of the processing (sample rates,
    bit widths, individual steps like "downsample", "LPF (fir N taps, halfband)" etc) and how...
  7. Hopefully I'll get round to looking at this -...

    Hopefully I'll get round to looking at this - perhaps I misremembered what the bandlimited stuff does for DC offset.
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    A think you need an I2S object in their to start...

    A think you need an I2S object in their to start the audio interrupts.
  9. For high speed logic you normally make every 2nd...

    For high speed logic you normally make every 2nd or 3rd wire ground, so that every signal is next to a ground return.

    But how fast are the signals involved? You can probably just distribute the...
  10. I suspect the "pop" is mainly the low frequency...

    I suspect the "pop" is mainly the low frequency component of a discontinuity - as I remember it the standard pulse waveform
    has DC offset unless at 50% duty cycle - the bandlimited implementation of...
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    No, thats not really what I meant. The schematic...

    No, thats not really what I meant. The schematic of some DSP follows the signal, as in "signal processing", showing the
    flow of information through functional blocks (a schematic or high-level...
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    This is how I'd do it: long bpm =...

    This is how I'd do it:


    long bpm = encoderCount ;
    float tempo = 1e6 / (bpm / 60.0); // beat period in microseconds
    unsigned long interval = (unsigned long) (round (tempo / 24.0));

    ...
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    I think this is just memory use, I see it jam...

    I think this is just memory use, I see it jam with 2 copies of the bandlimited waveform - it works with only one copy,
    and the memory is very tight:


    It works with two bandlimited waveforms and...
  14. Thread: Pwm

    by MarkT
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    184

    You know how to get twice the bit depth by using...

    You know how to get twice the bit depth by using two PWM pins? http://www.openmusiclabs.com/learning/digital/pwm-dac/dual-pwm-circuits/index.html
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    Schematic of the DSP ought to be clear - an...

    Schematic of the DSP ought to be clear - an overview of how it all connects together as orientation - its hard work
    just reading code from cold.
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    It was probably getting out of step because some...

    It was probably getting out of step because some interrupts were dropped as they came in while the previous one
    was still being handled, like I said. You don't get indefinite length queues for...
  17. The first thing to do is check the pinout of the...

    The first thing to do is check the pinout of the encoder by buzzing it out with a multimeter or
    continuity tester. You need to start by being certain which pin is which and connect to A, B, gnd....
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    The datasheet at least draws the schematic the...

    The datasheet at least draws the schematic the right way round(!) And it has a PCB layout which you would
    do well to follow verbatim.

    Maybe add schottky protection diodes on the audio lines. ...
  19. Can you explain why this would be advantageous to...

    Can you explain why this would be advantageous to you?
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    Looks great - I'm very tempted to build one - I...

    Looks great - I'm very tempted to build one - I don't really need one, but I'm still very tempted!
    One thought is that by replacing the opamps with something like the AD8656(*) you'd have enough...
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    On the ATmega328 multiple interrupts of the same...

    On the ATmega328 multiple interrupts of the same interrupt vector are discarded - not queued. It
    only queues interrupts of different types (in other words the queue has one entry per vector).
    ...
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    Could you put a block schematic for the DSP used...

    Could you put a block schematic for the DSP used in the README file, and it needs high-level comments
    and API spec. - this all goes in gui/index.html ultimately of course.
  23. You need to programmatically change the data used...

    You need to programmatically change the data used for touch event mapping when you change which form is
    presented on the screen. If you make this data-driven this will be more straight-forward. ...
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    Digital isolators, not opto-isolators. They are...

    Digital isolators, not opto-isolators. They are 1Mbps and up and logic inputs/outputs. They are becoming affordable and available
    in a mix of directions per chip.

    For instance:...
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    I did notice somewhere in the LiquidCrystalFast...

    I did notice somewhere in the LiquidCrystalFast code something like:


    digitalWrite (pin, HIGH) ; // pulse for at least 450ns
    digitalWrite (pin, LOW) ;

    which will obviously break on the...
  26. You are flushing every sample to SD card,...

    You are flushing every sample to SD card, flushing may involve several segment writes, segments are 512 bytes each.

    Better to flush regularly in time, such as every second, than every sample.
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    This sounds like a job for digital-isolators,...

    This sounds like a job for digital-isolators, galvanic isolation for motor drivers is good to have anyway.
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    You haven't posted your code so we can't see...

    You haven't posted your code so we can't see where the problem is. You also need to show the connections you are using
    as there's more than one way to connect and some are inherently slower. The...
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    T4 GPIO pins programmable output drive is from...

    T4 GPIO pins programmable output drive is from 1mA to 4mA... That's why I said 5mA is a tad high.
    I'm fairly sure it can handle 5mA with some voltage droop, but I wouldn't want to risk heavily...
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    The datasheet mentions 5mA a lot in the specs,...

    The datasheet mentions 5mA a lot in the specs, which is a tad high for T4, but ought to work at that level. I wouldn't try to push it harder
    per pin. Never connect an LED without limiting resistor...
  31. Thread: BOM Teensy 3.2

    by MarkT
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    They aren't, there's just some part numbers or...

    They aren't, there's just some part numbers or values on the layout image. For instance the USB connector has no part number
    and I wouldn't like to have to search through the many available to try...
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    Ah, those prominent caps must be decouplers...

    Ah, those prominent caps must be decouplers then...
    I think there is indeed a gap for a DC analysis object, AudioAnalyzePeak takes the absolute value, and of course
    RMS cannot be negative.
    ...
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    Place in a metal box with ferrite toroid on the...

    Place in a metal box with ferrite toroid on the USB cable?

    A different T4 with audioshield and HX8357D TFT attached:
    23891

    I think that one was programmed for 150MHz
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    Link to the display details?

    Link to the display details?
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    Spectrum from my SSA3021X using small B-field...

    Spectrum from my SSA3021X using small B-field probe 1cm above T4.0:
    23890

    background level from same probe:
    23889

    These are 0 -- 2.1GHz range, with T4 running at 600MHz clock.
  36. Circuit, code. Otherwise we've no information. ...

    Circuit, code. Otherwise we've no information. This could easily be either hardware or software problem from the description,
    so both are needed.
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    The inputs are likely to be AC coupled.

    The inputs are likely to be AC coupled.
  38. No, I said _without scrolling_ - just output line...

    No, I said _without scrolling_ - just output line by line (its quite so nice, but its usable).
  39. I think I did measure the performance of the...

    I think I did measure the performance of the various FFT types a while back on the T4, though I guess it matters more
    on slower chips - I only have T4.0 and T3.2 at the moment to play with.

    The...
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    Well I guess you just have to assume they are the...

    Well I guess you just have to assume they are the same, or close enough, and apply the equations anyway - the
    test circuit is ratiometric so the absolute resistance isn't important.
  41. You can implement a waterfall without scrolling...

    You can implement a waterfall without scrolling...
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    Because chips like this are synthesized from...

    Because chips like this are synthesized from hardware description libraries shared between many other chips, the
    silicon foundaries don't start afresh for each design, they have libraries of...
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    Resistive touchscreens are an overlay, typically...

    Resistive touchscreens are an overlay, typically having a 4 wire flat-flex cable going the PCB in a different place to the
    main CoG flatflex.
  44. Hard to guess if you don't follow the forum rule...

    Hard to guess if you don't follow the forum rule and post your code... What kind of noise? Do you have any
    data/graph/spectra to show?
  45. A and #A form a pair, B and #B form a pair -...

    A and #A form a pair, B and #B form a pair - those can be routed as twisted pairs, but twisting A with B will risk
    crosstalk between the quadrature channels.

    Each RS422 pair needs termination...
  46. Comparisons of the generic fft v. the existing...

    Comparisons of the generic fft v. the existing FFT1024, for several windows, with
    input being 5 test tones at -1dB, -20dB, -40dB, -60dB and -80dB compared to full scale sine.

    23877

    Notable is...
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    Unplug it, stick a multimeter on X-/X+, and...

    Unplug it, stick a multimeter on X-/X+, and Y-/Y+...
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    Had another look at the XPT2046 library code and...

    Had another look at the XPT2046 library code and it doesn't calculate Z values as per the datasheet, so its
    sentitivity is inherently poor in one corner. The raw readings of x, y, z1, z2 have to be...
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    The T4 is a dual issue processor so you can get...

    The T4 is a dual issue processor so you can get upto 1200 million instruction cycles per second with luck,
    but yes the clock period is 1.67ns = 1/600000000s, so 9 clocks is 15ns
  50. Timer1.initialize(10000000); // 1 Hertz ...

    Timer1.initialize(10000000); // 1 Hertz

    That's 10 million, not 1 million.
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