Search results

"The Free Software Foundation urged developers to choose or any later version..." [gnu.org] but if developers did not so choose, are the terms not precisely as they are written? While FSF may consider it bad, I'm not sure I see an ambiguity in that language itself. If there is ambiguity, it...

On the T3.2, the large numbers near 4M would make sense if instead of + pulse width, it was counting - pulse width (duration from falling edge to next rising edge). It works out to be about right for the typical interval between pulses, which often come about 10 to 20 per second.

Update: I found my T4.1 board and ran the same code on it, with the same source signal of pulses. The T4.1 has higher resolution by counting a faster-running clock. It still has the too-large-number glitches described above, but they are far more rare; only two cases out of over 30000 samples...

In case of interest, here's a histogram of pulse lengths captured by the above code. In this case, pulse length is some function of gamma ray energy, and the rightmost peak around 580 counts on the horizontal axis is due to a small Cs-137 test source emitting gammas near my detector. The...

I'm wondering if you might comment on what I'm seeing. I have pulses typically around 5 microseconds in length, on average about 20 of them per second, but each one arrives at a truly random time (this is a gamma scintillator, timing is random like a geiger counter). My code nominally works as...

Very helpful, thank you! It appears I am looking for the MARK version:

I'm wondering if there is some example Teensy 4 code that demonstrates how to measure a positive-going pulse width (as distinct from either pulse position, or frequency) with the best available accuracy, which I presume would mean hardware input capture to avoid uncertain interrupt latencies. In...

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 Vref Out of the chip (2.5 V) and the low side goes through 10k to ground. So I have R1, R2, R3 in...

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: https://forum.pjrc.com/threads/71064-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 first putting the 0x02 data register address into the COMMS register for each read, but in the...

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 mode would get you faster still, but this is actually...

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 usec) 3) wait a millisecond 4) read the 3-byte error register...

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, I think the chip can take SCLK up to 5 MHz (minimum t3 = t4 = 100 ns). Also, the chip has a...

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 sps. Using the "continuous conversion" mode and whether or not I wait for a sample to complete, I...

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 than 0.4 PPM so that looks reasonably stable to me. The data plotted comes from running curl...

Your solution is great; thank you! I wasn't even aware of 'jq' prior to this.

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 to programmatically retrieve one of those stats, every so often. My first thought was to simply...

"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 something to do with the crystal frequency stability vs. temperature, causing an external I/O data...

I'm guessing this is not a regular distributor? https://www.aliexpress.com/item/1005003039780539.html

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 frequencies, or simply the actual overall gain of the channel. Is it possible there is a...

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 results, with a rooftop antenna. My receiver is limited to the original US GPS constellation only, but...

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.

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 what I can see in the photo, you have used the header pins in a non-standard way. If you have not...

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 similar experiments and found my cellphone camera can see 850 nm LEDs, but it will NOT see 940 nm...

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 you will be clamping that digital output pin at 1 diode-drop (0.7 V or so) above ground and it will...

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: https://www.lrapa.org/DocumentCenter/View/4147/PurpleAir-Correction-Summary With that correction factor, my...

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 one as well, I guess I could figure out how much external airflow gets into the house.

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 there is a reason that her eyes are watering.

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 filter unit on order, as do I think a lot of other people right now. It's interesting to see how...

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 WA, than OR where perhaps most of it came from. Sorry about that! Of course PM2.5 is only one...

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 it outside briefly and then back inside. When I first tested it a few months ago, the reading...

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 forum didn't yet exist, or at least I didn't know about it, so I posted my test ADC code and results...

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 sensor, and the temperature gradients and rate of change with time are low enough, that it may be...

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 61.2 C and the frequency drift is near +8.612 ppm, with stability near 0.005 ppm in one hour...

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 as the ambient temperature. When I left the office with the door closed overnight, the error was a...

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 stabilized. I'd expect the main contribution to frequency drift for a simple crystal source to be...

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 if my GPSDO has far too little low-pass filtering to smooth out the timing shifts as individual...

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 antenna, providing a stable PPS signal. Unfortunately, that model speaks its own UCCM protocol...

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 the exact top of each NTP second, is that possible? To get up to speed...

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 with a lightly loaded LAN and whatever hardware they think of as "inexpensive oscillators". BUT I...

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 controlled in a PLL then I don't know. I have a GPSDO fed from a roof-mount antenna, and a Teensy 4.1...

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 post "Phase offset: Teensy vs PPS" ...if you are taking a PPS signal direct from a GPS, especially...

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 frequency switching going on all over the T4.x chips). Using an external ADC makes it much...

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, and/or slow response with a filter capacitor, due to RC time constant). Normally with such a high...

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); pinMode(A2, INPUT_DISABLE); pinMode(A3, INPUT_DISABLE); This made a BIG difference to sensor...

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 is named DataLogger.h with a...

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 intermediate Serial.print() statements, just incrementing the histogram array internally and...

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 tend to be the weakest link in a system if you do a whole lot of writing to them.

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 specifically values 15, 31, 47, 63 and so on) is...

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 around 1 kHz using this code: // testing Teensy 4.1 ADC...