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    Here is some measured data on noise performance...

    Here is some measured data on noise performance at Gain = 1.
    I was looking at RMS noise on Ch.0 (differential input pins AD0 and AD1) with 10 ohms across them.
    The high side goes through 10k to the...
  2. Just for reference, today I made a sketch without...

    Just for reference, today I made a sketch without using any library beyond the plain SPI device, that does achieve 19.2 kHz reads with this chip. That post is here:...
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    AD7124 code example at maximum speed

    I'm sure people have done it, but I did not find a code example to demonstrate using the 24-bit ADC chip AD7124 in its "continuous read" mode at the maximum speed.
    Normally the data is read out by...
  4. experiment with removing 1 msec delay

    I was able to get 4.4 kHz readout at a filterWord of 2, by simply removing the 1 msec delay in ad7124-private.cpp Ad7124Private::waitForSpiReady and waitForConvReady
    Using the simple continuous read...
  5. detailed timings on AD7124 SPI bus

    In case of interest, my Saleae logic analyzer says the reading loop in my test code goes like this, on the SPI bus:

    1) wait a millisecond
    2) read the 1-byte status register 0x00 (3 bytes, 25.4...
  6. Thanks for having a look Paul. Still can't...

    Thanks for having a look Paul. Still can't believe how much of your life must be debugging random other people's problems.

    Yes, that's the one I'm using, AD7124-8. Good point about the SPI clock,...
  7. AD7124 (24-bit ADC) and epsilonRT library : how fast will it go?

    I'm just curious if anyone has used this AD7124 24-bit ADC at higher data rates, for example 1 kHz or above. The Analog Devices AD7124 datasheet claims it is capable of sampling rates up to 19200...
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    Here is a plot of my Teensy's onboard crystal...

    Here is a plot of my Teensy's onboard crystal drift during 34 hours after a restart. (At least, I think this TeensyNTP-reported value is the onboard clock drift). Total change over that time was less...
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    Your solution is great; thank you! I wasn't even...

    Your solution is great; thank you! I wasn't even aware of 'jq' prior to this.
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    I'm running the T4.1 NTP server and it has been...

    I'm running the T4.1 NTP server and it has been working well. I can load the server webpage and see the charts and the text stats at the bottom of the page OK. I'm wondering if there's an easy way...
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    "This problem works running the sketch from...

    "This problem works running the sketch from 150Mhz to 600Mhz at the same temperature, and it seems to not be related to the frequency." If it's independent of the CPU setting, I wonder if there is...
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    Teensy 4.1 on AliExpress ?

    I'm guessing this is not a regular distributor?
    https://www.aliexpress.com/item/1005003039780539.html
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    If both the noise and the 60 Hz pickup change by...

    If both the noise and the 60 Hz pickup change by a factor of 2, that sounds like the different sampling configurations are somehow either changing the effective impedance of the ADC input at those...
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    I had not been keeping track of developments; I...

    I had not been keeping track of developments; I only just saw the T4.1 NTP server code was updated to include the webserver with some plots and numbers. In case of interest here are my current...
  15. pins soldered to Teensy board

    I did a sloppy job of soldering the pins on this old Teensy board (and by now it's also covered with dust) but hopefully you see how the pins are soldered to the board here.
    25660
  16. Glad you have a scope, that is the right tool for...

    Glad you have a scope, that is the right tool for this job. Have you probed the metallized ring around the hole at each output of the T4 board itself to see if the signal is present there?

    From...
  17. Using a phone camera to see IR is kind of a...

    Using a phone camera to see IR is kind of a "hack" or a cheat, which sometimes works, but it will probably not work in this case.

    I see from your datasheet you are using 940 nm LEDs. I have done...
  18. I'm more used to seeing NPN transistors drawn...

    I'm more used to seeing NPN transistors drawn with the emitter pointing down, but I guess it's just a tradition. If you connect the base of the transistor directly to the output pin of the Teensy...
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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...
  33. 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...
  36. 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...
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    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...
  40. 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...
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  50. > "...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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