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    • M
      MarkT replied to the thread Teensy 4.1 Inputs and Outputs.
      Do you mean the audio adapter? That has one microphone input, but two two line inputs. There are other options for interfacing to microphones, and yes that would be a separate board - any I2S compatible audio chip pretty much can work. Or you...
    • M
      You need to get knobs on those pots! Watch out for loose wires if you remain with it breadboarded - a more permanent construction will pay off the first time it gets dropped perhaps! I suspect your volume issue is the pots are linear and you...
    • M
      Mmmm, some nice sounds - perservere! Kickstarter?
    • M
      MarkT replied to the thread FlexCAN_T4 - FlexCAN for Teensy 4.
      That's a good excuse in my book.
    • M
      MarkT replied to the thread Teensy 4.1 stalls?.
      You'll need to protect the teensy and its wiring from the EMI produced by the blower motor. Is the teensy in a grounded metal box? That's the bare minimum you need to do.
    • M
      On a modern logic chip 2pF is a lot of area. The usual unit for measuring component capacitances on a VLSI chip is the femtofarad!
    • M
      Many more much smaller decoupling caps (10nF 0402?), one for each via that needs it? - that's how its usually done. 4- or 6-layer boards are typically needed for BGA devices. Large decoupling caps typically are further out as they can afford a...
    • M
      Can you expand those traces so we can see the edges in more detail please?
    • M
      The TL431 is a reference, not a logic level converter, its probably a 100 times too slow on the edge transitions to produce reliable clocking - go with suitable 5V tolerant logic families like 74LCX, 74LVC with strong hysteresis, the 74LVC14 hex...
    • M
      MarkT replied to the thread Humidity issues.
      Seriously consider a hermetic enclosure for the teensy in a marine environment, no connectors handle salty air well, unless you pot them and put them beyond use! For everyday rain exposure the push button needs to be IP68 or similar I think...
    • M
      MarkT replied to the thread FlexCAN_T4 - FlexCAN for Teensy 4.
      mHz is millihertz, MHz is megahertz, megax...
    • M
      And the simpler solution for a slow-changing analog input is to put 100nF or so to ground on the input pin - this will present a low impedance on the timescale of an ADC conversion, and is one extra component. Typical sampling caps in modern...
    • M
      MarkT replied to the thread 5-DRV8825 Questions.
      Microstepping reduces the tendancy to miss-step, so it usually increases the _usable_ torque. 60 rpm is within most stepper's power band (torque can drop off very rapidly with speed at a few hundred rpm). Dynamic torque is a lot less than...
    • M
      I'm pretty sure there's only one ground on the audio adapter. The SGTL grounds are normally star grounded together to a single ground plane - at least that's the datasheet recommendation. (Well to be precise there is a separate headphone analog...
    • M
      I thought CMSIS had all the relevant vector operations like complex magnitude? I do know T4 only out of the box supports a certain version of CMSIS, perhaps that's the issue?
    • M
      FIR filters don't have to be linear-phase though - its not clear if there is a requirement for linear-phase, but the phrase real-time suggests its not such a priority? Partitioned convolution can give upto 0 sample latency if done the right way...
    • M
      Which rather rules out the naive FFT/zeroing/IFFT approach as its not real-time, suggesting you require either a FIR filter (limited by performance as number of taps increases), or a filter done with fast convolution (partitioned convolution for...
    • M
      For large numbers of FIR taps its best to use FFT based convolution - there are various threads here about this, I doubt there's a particularly simple one - try searching "partitioned convolution" perhaps?
    • M
      MarkT replied to the thread Realistic max SPI clock rate?.
      Much higher so long as you have signals over a groundplane at a reasonable impedance, and you can add good (low inductance) decoupling to chips with SMT caps and low-value series resistors on datalines to reduce ringing.
    • M
      MarkT replied to the thread I think my Teensy 4.1 is broken.
      Please give measurements in numbers, rather than "none in 3V3" - is this 0.00V, 0.0V, 0.1V ,0.5V? This level of detail is usually very revealing. If its 0.1V or less I'd suspect a hard short somewhere, you have to find it and fix it - the...
    • M
      MarkT replied to the thread Realistic max SPI clock rate?.
      And working on a breadboard its wise to stick to below 30MHz anyway - I never got anything digitls to work reliably above 40MHz in that environment (due to lots of parasitic impedances).
    • M
      Magnetic field strength falls as the inverse-cube of the distance from a magnet, once far enough away for it to look like a dipole. To the best of our knowledge magnetic monopoles don't exist - if they did they would have an inverse-square law...
    • M
      The MAX4466 is not low noise by any criterion, it has a whopping 80nV/√Hz, whereas a run-of-the-mill low noise opemp will get you to more like 4nV/√Hz, a full 26dB quieter. Just because the marketing department put "low noise" or "microphone...
    • M
      MarkT replied to the thread Hookup Teensy 4.1 to Tda 2030.
      The line out connections from the audio adapter are the correct ones to use - do not use the headphone output except for headphones/earphones, it needs to isolated from ground. With one speaker just use one channel, don't short them together.
    • M
      Keepers pull both up and down, depending on what the voltage is. That's how they "keep" the pin voltage (stop oscillation or floating behaviour).
    • M
      Yes water soluable sounds good, or just use a no-clean flux?
    • M
      Its a strong alkali. (NH4+/OH-), strong acids and bases have no place in electronics, they can permeate the PCB material and hang around for ages too, especially acids which liberate free protons that can diffuse through almost any material...
    • M
      I suspect those cheap chinese buck converters don't have great layout and the result is instability, especially with the great reduction range you are needing, 12:1 or so. SMPS are very sensitive to layout.
    • M
      Can you point to the datasheet or pages about the buck converter you have? Some require minimum load and are not happy without this.
    • M
      MarkT replied to the thread JLCPCB Teensy Headers?.
      Conversely I find the turned pin sockets hard to use and often they bend an IC pin - the standard type seen better as they have a very wide path to accept a pin.
    • M
      Excellent to hear its useful and being used!
    • M
      MarkT replied to the thread Creating custom waveforms.
      It's called rate conversion, but its important to get it accurate to avoid artifacts, which means accurately measuring the sampled frequency. Hopefully whatever software you use for the rate conversion also has this as an option. Basically you...
    • M
      MarkT replied to the thread Small bandwith FFT analysis.
      You need a small FFT for faster analysis, maybe the FFT256 class. An FFT has to process all the samples however much of the spectrum you are interested in. Another approach is using a filter bank if you are only interested in.a few specific...
    • M
      Same SCLK defines it as one SPI bus surely?
    • M
      BTW it has 8 parallel SPI datalines, not "serial" in its usual meaning.
    • M
      Sounds like a job for the MQS feature. It uses noise-shaping to improve resolution and reduce quantization noise.
    • M
      Yes it works well for me - and QA are fast to respond to questions/suggestions
    • M
      Just use an external resistor driven from a different pin...
    • M
      That datasheet lists the bridge resistance as 350 ohms, so at 10V you'll see about 30mA.
    • M
      Internal pullups aren't resistors, they are FETs, they are non-linear and the value varies a lot between different chips - basically no use for measurements like this. On a CMOS chip a FET is perhaps 1000's of times smaller than a resistor....
    • M
      The green squares don't appear in the legend...
    • M
      This thread might be useful: https://forum.pjrc.com/index.php?threads/sample-code-using-gpio.61816/#post-246152
    • M
      Search for AudioMemoryUsageMax and AudioProcessorUsageMax for examples of logging memory and CPU usage. Band limiting consumes more resources (quite a lot more) than the plain waveform generation, so be suspicious of running out of CPU, not just...
    • M
      For 3.3V use try 240R and 120R for the divider. However this might be pushing T4 pins rather hard as they have limited current drive. A better solution might be this which only loads the pins with 7mA ohms, not 9mA, and relies on the receiver's...
      • P1050764.JPG
    • M
      MarkT replied to the thread Teensy 4.1 - NXP MIMXRT1062DVJ6B.
      Well 2007 is the standard year/week date code I think, I've a T4 U1 with DVL6A, 0N00X, CTBP1941E - CTxx may be a batch code, then YYWWD perhaps?
    • M
      So some chip that has an internal noise gate? Possible I suppose.
    • M
      Doesn't seem to be anything to do with the chip, which only enters power-save if the I2S clocks go away or are wrong. Adding a constant fixed offset to output _after_ the envelope shouldn't have any effect on the sound as the output is AC...
    • M
      You know the clear arrays code is absent? Could that be the issue? Can't see anything obvious otherwise.
    • M
      MarkT replied to the thread PWM Causing Jitter - Teensy 4.1.
      Firstly you cannot expect analog inputs to stay rock steady, if the voltage falls close to an ADC step it can jump back and forth by one count, this is a fundamental property of digitizing any signal. So normally hysteresis is added in the code...
    • M
      MarkT replied to the thread U2 and D4 hot, 3.3v shorted to GND.
      You can't measure resistance when the circuit is powered up. Measure the _voltage_ when a circuit is powered. 19 ohms is not a hard short, suggests a failed semiconductor, not a metal-to-metal short circuit.
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