Forum Rule: Always post complete source code & details to reproduce any issue!

Search:

Type: Posts; User: MarkT

Page 1 of 10 1 2 3 4

Search: Search took 0.01 seconds.

  1. Replies
    15
    Views
    218

    Programmers learn to be precise and methodical. ...

    Programmers learn to be precise and methodical. C++ was chosen I suspect because it uses very little runtime resources,
    and allows bare-metal control which is important for a microcontroller. Not...
  2. There are single pixel wide arrays that might be...

    There are single pixel wide arrays that might be relevant from what I recall. Due to the small number of pixels these
    are probably easy to use at high frame rates. Using IR illumination might be...
  3. 1) The Teensy should not be powering the motors. ...

    1) The Teensy should not be powering the motors. Separate supply is needed to prevent spikes/dropouts on the sensitive power rail.
    Motors draw much higher currents at stall (ie from standstill), so...
  4. The limiting factor is typically inductance - you...

    The limiting factor is typically inductance - you ideally want to run a ground wire between every pair of signal wires to provide
    low inductance return paths for each. Otherwise you'll get strong...
  5. Replies
    7
    Views
    96

    EMI absorbing sheets might be another approach,...

    EMI absorbing sheets might be another approach, such as Kemet FX5. Place behind the GPD antenna...
  6. The low-down on C literal syntax:...

    The low-down on C literal syntax: https://www.tutorialspoint.com/cprogramming/c_constants.htm

    (Although it only mentions the f suffix in an example of incorrect floating point, sorry about that! ...
  7. Linear regulators, not switch-mode. Decent...

    Linear regulators, not switch-mode. Decent decoupling for audio (ceramic 100nF + 100uF electrolytic for instance).

    For sudio signal pots use low values, 10k to 1k sort of range, to keep Johnson...
  8. Replies
    14
    Views
    243

    For transmission quality I don't think direct...

    For transmission quality I don't think direct from a microcontroller is clean enough, all that digital noise on the rails...

    Something like a DDS-60 module might be more reasonable, but with...
  9. Its saying the control voltage can be 3V to...

    Its saying the control voltage can be 3V to 10VDC. What can that mean other than input 4 can be upto 10V more positive than input 3?
    If that's the case, you don't have to worry.
  10. Replies
    14
    Views
    243

    BTW what signal quality requirements do you have?

    BTW what signal quality requirements do you have?
  11. "Control voltage range 3V to 10V" - that's pretty...

    "Control voltage range 3V to 10V" - that's pretty clear to me.
  12. Yes I think so, the risetime of the signal is not...

    Yes I think so, the risetime of the signal is not instantaneous, and the thresholding will likely be different for each microphone
    due to signal level variation. Cross-correlation uses all the...
  13. Replies
    23
    Views
    444

    This is the correct link,...

    This is the correct link, https://www.ap.com/blog/fft-spectrum-and-spectral-densities-same-data-different-scaling/

    The basic insight is that a discrete spectrum is measured differently from a...
  14. Replies
    7
    Views
    163

    3V is possibly not safe on low voltage CMOS...

    3V is possibly not safe on low voltage CMOS chips. Many standard multimeters use 0.2V full-scale except on diode mode.
    The 56k you see on the powered down chip is because you are back-driving the...
  15. Replies
    14
    Views
    243

    I've not played with the T3.6, but I wouldn't be...

    I've not played with the T3.6, but I wouldn't be surprized if you can generate suitable square waves from the PWM units in it?

    This thread seems relevant. ...
  16. I think you mean correlation, not convolution...

    I think you mean correlation, not convolution (very different things), and secondly its cross-correlation,
    an autocorrelation cannot be between two signals!
  17. Replies
    23
    Views
    444

    Let me say it again, FFT plots of signal spectrum...

    Let me say it again, FFT plots of signal spectrum are not useful for measuring noise floor, you need a PSD plot for that.
    Noise is measured in W/Hz, or V/√Hz, and an FFT bin is typically not exactly...
  18. Audio is an ac signal, typically I2S audio ADCs...

    Audio is an ac signal, typically I2S audio ADCs have a DC-removal filter built in so the result is strictly zero-centred.
    Oddly typical audio DACs are not DC-blocking, which is a problem (if the...
  19. Replies
    10
    Views
    236

    Hmm, perhaps that level shifter isn't able to...

    Hmm, perhaps that level shifter isn't able to drive the opto-coupler LEDs properly - can't see any
    datasheet for it. Opto coupled inputs probably want 15mA or so, which is more than some logic...
  20. Replies
    14
    Views
    243

    Sounds like a job for a DDS module, not a...

    Sounds like a job for a DDS module, not a microcontroller. Cheap AD9833 module perhaps?

    Or you could use square wave output and a high-order low-pass filter on the output to kill the harmonics.
  21. Replies
    14
    Views
    243

    Sounds like a job for a DDS module, not a...

    Sounds like a job for a DDS module, not a microcontroller. Cheap AD9833 module perhaps?
  22. Replies
    10
    Views
    236

    That's not a small motor. This is the small type...

    That's not a small motor. This is the small type of stepper: https://www.hackster.io/news/drive-a-tiny-stepper-directly-with-arduino-911571f8cd0e

    Try with AccelStepper library and 1000...
  23. Replies
    4
    Views
    155

    SDRAM needs about 26 pins to connect to it,...

    SDRAM needs about 26 pins to connect to it, several control lines and an 8-bit databus and 12 or so address bits.
  24. Replies
    5
    Views
    154

    You mention an existing diode, but don't...

    You mention an existing diode, but don't explain...
  25. Replies
    57
    Views
    3,139

    For a strain-guage wheatstone bridge...

    For a strain-guage wheatstone bridge configuration you need an instrumentation amp to boost the differential mode signal.
    There are many instrumentation amps you can get, its basically 3 opamps in a...
  26. Replies
    24
    Views
    974

    If you want to integrate pulses, use an...

    If you want to integrate pulses, use an integrator before sampling. Then you need a much lower sample rate.
    The pulse time can be captured with a comparator, the pulse energy by differencing the...
  27. This is the classic scheduling problem, and a...

    This is the classic scheduling problem, and a good data-structure to use is a heapsorted list, aka binary heap.

    inserts and extracts are O(log(N)) so it scales well to 100's or 1000's of entries,...
  28. I guess I was saying either use a standard...

    I guess I was saying either use a standard Bressenham's or write something cleaner without the arbitrary mix of global variables and
    passed arguments. For me a nice clean interface would be a...
  29. Replies
    10
    Views
    236

    Indeed you'll never get a stepper to jump to high...

    Indeed you'll never get a stepper to jump to high speed from standstill without speed ramping, unless its a really tiny motor.
  30. Replies
    23
    Views
    444

    Most 'scope front-ends aren't linear enough for...

    Most 'scope front-ends aren't linear enough for any kind of audio quality measurement work! They are designed for a large bandwidth with constant group-delay,
    and are typically 8-bit so only have...
  31. Replies
    24
    Views
    974

    10MSPS ADC needs a separate (presumably parallel)...

    10MSPS ADC needs a separate (presumably parallel) ADC chip and you need a datapath for it too, this is high speed acquisition.
    FPGA's are often used once you get to these kinds of speeds as the...
  32. Replies
    15
    Views
    410

    All pn junctions are photodiodes and LEDs, if the...

    All pn junctions are photodiodes and LEDs, if the material is transparent at the relevant wavelength, since photons generate
    electron-hole pairs and recombination can emit a photon (although the...
  33. Replies
    13
    Views
    325

    I think you'll need to do some low-pass filtering...

    I think you'll need to do some low-pass filtering then. Try an RCRC to start with, that might have enough roll-off and
    is very simple. For differential RC filter you have two resistors and one...
  34. The logic doesn't look good in...

    The logic doesn't look good in linearInterpolation... First you are not dealing with any edge cases, such as when X_old == pTS.x.
    Second you are overwriting wave1Values[Xold] the first time round...
  35. The default volume is 0.3 and 4 x 0.3 > 1.0 so...

    The default volume is 0.3 and 4 x 0.3 > 1.0 so your mixer output is clipping I think. Try 0.25.

    Ah, but I think your oscillators are at 0.3 already so that won't be it....

    Ah, looked again,...
  36. Replies
    14
    Views
    466

    I'd say should use, not must use :) For low...

    I'd say should use, not must use :)
    For low voltage circuitry many old style opamps are bad news as they require dual rail supplies - a modern
    true rail-to-rail audio spec'd opamp is a better...
  37. Replies
    13
    Views
    325

    Absolutely not, you'll be driving them into...

    Absolutely not, you'll be driving them into slew-rating limiting which is massively distorting (the feedback loop
    completely loses lock). Also the step change in input may destroy the front-end of...
  38. Replies
    13
    Views
    325

    That 33uF on the output of the buffer should...

    That 33uF on the output of the buffer should definitely not be there! Opamps don't drive capacitive loads!
  39. Replies
    14
    Views
    466

    Inductance is measured in henries, not farads... ...

    Inductance is measured in henries, not farads... 33ÁH perhaps?

    If you drive audio amp from a switch-mode supply (not recommended), then make sure its one with an
    ultrasonic switching frequency...
  40. Replies
    13
    Views
    325

    Ah, xyproblem again. You can't process the...

    Ah, xyproblem again.

    You can't process the output of a class D amplifier in the analog domain as its a digital signal.

    First you need to low-pass filter the signal.
  41. Replies
    13
    Views
    325

    The MCP6002 won't do audio, far too slow(*). ...

    The MCP6002 won't do audio, far too slow(*). Its an ultra low power opamp, so the bandwidth and slew-rate are woeful.

    Your virtual ground reference network, the two 47k resistors, lacks...
  42. Replies
    9
    Views
    198

    Is this a layout issue? Cables too long? ...

    Is this a layout issue? Cables too long? Missing or misrouted ground return wire?
  43. Replies
    91
    Views
    6,496

    If you want to find out more, this is the paper...

    If you want to find out more, this is the paper that inspired me: https://holometer.fnal.gov/GH_FFT.pdf
  44. Replies
    25
    Views
    6,326

    The PCM1808 datasheet clearly shows the analog...

    The PCM1808 datasheet clearly shows the analog supply is 5V and digital 3.3V. If a module doesn't have a separate regulator
    on it then both voltages need to be brought into the module.

    Its...
  45. No, you want to reduce the sampling rate or...

    No, you want to reduce the sampling rate or increase the number of FFT bins or both.
  46. The FFT output is always equally spaced frequency...

    The FFT output is always equally spaced frequency bins, nothing you can do to change that, you simply want
    to present that information recscaled logarithmically. For each x position map to an...
  47. Then you'll need to map your x coord to frequency...

    Then you'll need to map your x coord to frequency through an exponential function, and use that to decide which FFT bin corresponds
    to that frequency. And you'll probably want to interpolate...
  48. Replies
    91
    Views
    6,496

    I'm just trying to correct the common...

    I'm just trying to correct the common misconception about noise-floor measurements using the FFT - its very
    rarely appreciated that noise isn't measured the same as a single tone. Noise is measured...
  49. Replies
    91
    Views
    6,496

    Noise floor is measured as power spectral...

    Noise floor is measured as power spectral density, that plot is showing the power spectrum w.r.t. the loudest tone, so the
    -78dB isn't meaningful as a measure of noise, since changing the FFT number...
  50. These are CMOS isolators, not opto-isolators, so...

    These are CMOS isolators, not opto-isolators, so standard CMOS input and output behaviour. Outputs good to 4mA from
    what I can tell, fine for any logic input. The WS2812 input is just CMOS logic...
Results 1 to 50 of 500
Page 1 of 10 1 2 3 4