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    FWIW, apparently my PMS5003 sensor (also used in...

    FWIW, apparently my PMS5003 sensor (also used in the "PurpleAir" monitor) yields numbers around 2x higher than the official EPA PM2.5 values for woodsmoke particulates specifically:...
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    Interesting to see how things change over time,...

    Interesting to see how things change over time, with the sensor in one location in the living room. Inside reading peaked this morning near 300 around 5 am. If I had a continuously running outside...
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    Using a T4.1 with its handy built-in SD card...

    Using a T4.1 with its handy built-in SD card holder, I made a data-logging version in a cardboard box, and it went on a trip in the car to DG's ("doting grandma") place and back, and sure enough...
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    You show a very nice setup and some great data!...

    You show a very nice setup and some great data! Right now I'm making a portable logging setup with another Teensy and PMS5003 to compare readings at my place with my mother-in-law's. We have a HEPA...
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    Happily it's cold and foggy just south of...

    Happily it's cold and foggy just south of Portland right now, which is helping slow the fires. Looking at the satellite map, changing winds are pushing the brownest-looking smoke more into western...
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    PM2.5 air quality monitor - Oregon fires

    Photo shows a T3.1 hooked up to a Plantower PMS5003 air quality particulate sensor https://aqicn.org/sensor/pms5003-7003/ and a small OLED display to graph the reading vs time. I had it inside, took...
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    Teensy 4.x are more powerful but Teensy 3.x have...

    Teensy 4.x are more powerful but Teensy 3.x have lower noise ADCs, due to the usual design tradeoffs about processor speed and high-current switching noise.

    When I first got a Teensy 3.0 this...
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    Well, I am cherry-picking the best few hours I've...

    Well, I am cherry-picking the best few hours I've seen so far, but the concrete block is pretty effective in slowing down temperature changes. It appears to me if I had a high-resolution temperature...
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    After a few days of sitting in a concrete block,...

    After a few days of sitting in a concrete block, which is in turn inside a large styrofoam box, the T4.1 temperature and frequency drift has mostly stabilized. Its reported CPU temperature is around...
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    With more data, I see my wild surmise about my...

    With more data, I see my wild surmise about my GPSDO was wrong, and your more obvious suggestion was correct. Almost all the variation I saw was explained by air movement over the T4.1 PCB, as well...
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    I have done no investigation yet, so I certainly...

    I have done no investigation yet, so I certainly don't know the cause of that behavior. Normally you expect a GPSDO to be much more stable than a simple SMT oscillator that isn't even temperature...
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    Thank you for that reply. Plotting the drift and...

    Thank you for that reply. Plotting the drift and chi-sq values over two hours, I see the drift is nothing like the random-walk noise I expected. Instead it is dominated by sudden dramatic shifts, as...
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    I've got a start, at least. The code runs on my...

    I've got a start, at least. The code runs on my T4.1, and ping to it from another host shows a smaller RTT than anything else on my LAN (avg = 0.186 msec). I have a Trimble 57964-80 GPSDO with roof...
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    PTP client possible?

    Is it correct to say that this code acts as a PTP server only, and not a client? For example, if I have two T4.1 boards and I want board #2 to receive time over a LAN from board #1 and blink a LED at...
  15. A good implementation of PTP "should" be able to...

    A good implementation of PTP "should" be able to achieve sub-microsecond timing synchronization over a LAN. Agilent said in 2005 their experience with PTP / IEEE1588 is ~ 0.1 microsecond accuracy...
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    I would expect almost any un-corrected crystal...

    I would expect almost any un-corrected crystal oscillator to have better short term jitter than a raw GPS PPS signal, although of course worse over some longer term, but when the oscillator is...
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    This is amazing work, thanks for posting this! I...

    This is amazing work, thanks for posting this! I noticed the 1588 hardware features listed for the T4.1, and I wondered if they would be supported in some way.
    On the first graph in your first...
  18. If you want high-quality ADCs for audio signals,...

    If you want high-quality ADCs for audio signals, you do not use anything inside the Teensy (and the Teensy 4 ADCs are worse than T3.x; as you'd expect from the noise coupling from higher-current high...
  19. What resolution and sample rate or bandwidth do...

    What resolution and sample rate or bandwidth do you need? You could simply put a 1M resistor in series, that would make your sensor happy, but the Teensy ADC unhappy (either extremely high noise,...
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    Two possibly worthwhile changes I made to the...

    Two possibly worthwhile changes I made to the basic logger. In the setup() part:

    pinMode(A0, INPUT_DISABLE); // 4 ADC inputs without digital "keeper" drive on pin
    pinMode(A1, INPUT_DISABLE);...
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    DataLogger.h file capitalization seems to matter, on Linux at least

    Just getting started trying out this interesting project.
    My first issue: provided examples fail to compile because #include <Datalogger.h> file is not found.

    Reason: capitalization. Actual file...
  22. I did try the same program & setup with the...

    I did try the same program & setup with the processor set to 528 MHz. The results look about the same, with the same comb-filter spikes spaced 16 units apart at 15, 31, etc.
    I also tried without...
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    Sorry to be slightly off-topic, but do you...

    Sorry to be slightly off-topic, but do you data-acquisition folks have a type or brand of SD card you're happy with? In my experiences with other hardware (Raspberry Pi) it seems these memory cards...
  24. Teensy 4.0 ADC histogram without averaging

    Running the same code as in my previous post, on Teensy 4.0 board shows a different pattern than on T4.1. On the Teensy 4.0 board, every 16th ADC value, that is ADC readings of the form (16*n - 1) or...
  25. histogram test of 12-bit ADC on T4.1

    I tried out a new Teensy 4.1 that came in the mail today, with Arduino 1.8.12 and Teensyduino 1.52-beta6.
    I accumulated a simple 4096-bin histogram of raw samples without averaging, for 200k samples...
  26. At the time I was testing T4beta1 the ADC library...

    At the time I was testing T4beta1 the ADC library wasn't supporting T4 yet so I didn't use it, and I did not see the 8-sample gap each 256 steps that you describe. I had averaging on, but I believe...
  27. FWIW here is what leaving the "keeper" port...

    FWIW here is what leaving the "keeper" port setting on looked like on my T4.0 beta: https://forum.pjrc.com/threads/54711-Teensy-4-0-First-Beta-Test?p=198315&viewfull=1#post198315
    It had the effect...
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    I remember playing with an Exidy Sorcerer one...

    I remember playing with an Exidy Sorcerer one summer, on loan from a family friend. That was the first computer we had in the house; maybe a year before we got our own Apple II. I remember the...
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    I am curious what amount of gyro drift is...

    I am curious what amount of gyro drift is considered OK. Recently I was playing around with the Lego Mindstorms Gyro Sensor, which connects to their EV3 controller. I don't know what gyro chip they...
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    As far as I know, getting data at a high, fixed...

    As far as I know, getting data at a high, fixed rate of speed is what DMA is intended for.
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    I believe that is exactly what I did, 100 kHz...

    I believe that is exactly what I did, 100 kHz sampling on both ADC_0 and ADC_1 using the "adc_pdb" library example and modified as I showed in my last post. However this code simply reads the data...
  32. > "...There are many devices that transfer...

    > "...There are many devices that transfer continuously over the USB bus at high-speed and do not hang..." I'd be interested if there are any examples using the USB device type Teensy 4 currently is....
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    I think T4 GPIO pins are on a 150 MHz clock,...

    I think T4 GPIO pins are on a 150 MHz clock, meaning sequential writes might be 6.67 nanoseconds apart.
    Choosing a random NEMA17 stepper, I find coil R,L specs at R=1.1 ohm and L=2.6 mH. The time...
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    Using a modified adc_pdb example from the ADC...

    Using a modified adc_pdb example from the ADC library and setting 100kHz sample rate, with the LED pin 13 toggling each sample. I am using a scope triggered on the pin 13 signal, and then zooming in...
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    checking out the new T4 ADC library

    Thank you very much for getting this going! I think I installed it as directed, but I am wondering which examples should work.

    "adc_pdb" only works if you comment out the pdb_isr() function,...
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    If you need a DAC for DC level output there are...

    If you need a DAC for DC level output there are plenty of outboard options to choose from, with various interfaces, speeds and accuracy.
    For example just DACs that have 12 bit resolution, Vcc in the...
  37. I'm curious, there's a cesium clock that's very...

    I'm curious, there's a cesium clock that's very low power? Also, I would have thought underwater is the one place that a 30 C limit wouldn't be a problem.
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    Correct, analogRead() is a blocking call in my...

    Correct, analogRead() is a blocking call in my example, just as in all other Arduino-alike devices AFAIK. The return value is the ADC reading just made. It is not a terribly long delay on T4; less...
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    If you're curious, here's the implementation of...

    If you're curious, here's the implementation of ADC in the Teensy 4 core code: https://github.com/PaulStoffregen/cores/blob/master/teensy4/analog.c
    To (not) answer an earlier question, the adc.h...
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    You can use the A/D in the same way as with other...

    You can use the A/D in the same way as with other Arduino-style boards without a separate library. For example the below program compiles and runs on Teensy 4. Note that T3.2 has a nominally 16-bit...
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    There is no ADC library for the T4 yet that I...

    There is no ADC library for the T4 yet that I know of. I think what you want to do is relatively straightforward however. By the way, as I understand it, even the T3.2 ADC library did not do strictly...
  42. I was not aware of this idea before, it is very...

    I was not aware of this idea before, it is very impressive that it can be done very simply and relatively cheaply! Interesting to see your 3D printed wood PLA structure, which is also something new...
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    Which one is "that page" ?

    Which one is "that page" ?
  44. I understand your request was for an absolute...

    I understand your request was for an absolute time, or "time stamp" for each rising edge. What I read about that library https://github.com/PaulStoffregen/FreqMeasureMulti is that you get the count...
  45. (FWIW, reason the "Uno" did not work is it was a...

    (FWIW, reason the "Uno" did not work is it was a knockoff board "OPEN-SMART UNO" and actually used a ATmega168 instead of 328p, and the bootloader was set at 19.2kbps.)
  46. teensy_post_com at 100% CPU after closing out everything

    Maybe not helpful as I don't have much debug info. I'm running Arduino 1.8.9 / Teensydino 1.47 under Linux Mint on an Intel-based "fitlet2" mini-PC.
    Linux john-fitlet2 4.15.0-58-generic #64-Ubuntu...
  47. The Teensy boards were not designed for parallel...

    The Teensy boards were not designed for parallel I/O, I don't think there are 8 adjacent bits available. You could piece together things in software but don't know how it would work under DMA...
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    It does? I didn't even realize it. Ah, I guess...

    It does? I didn't even realize it. Ah, I guess you mean this: https://www.pjrc.com/tech/8051/index.html
    You might also note the bottom of that page: Last updated: February 24, 2005

    I don't know...
  49. The formula changes by vendor and this was...

    The formula changes by vendor and this was several years ago, but I think it was proportional to PCB area for a fixed number of layers, and some more complicated formula on total layers. I'm pretty...
  50. T4 ADC speed tests

    Running this code on a T4, it reports 174825 samples per second as shown with 12 bit resolution and analogReadAveraging(1). That works out to 5.72 microseconds per sample. It is also calculating...
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