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Type: Posts; User: ddrown

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    My two have a tempco of 0.154ppm/C and...

    My two have a tempco of 0.154ppm/C and 0.206ppm/C, so that fits with your 0.195ppm/C.

    Wander being 0.005 ppm in an hour is pretty impressive.
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    Nice! Good idea with the cinderblock, that should...

    Nice! Good idea with the cinderblock, that should add a lot of thermal mass
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    I'm curious why you assume the frequency changes...

    I'm curious why you assume the frequency changes are coming from the GPSDO and not from the Teensy's crystal. Could you explain why you suspect the one but not the other?
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    chisquare values are in counts (25MHz) so 42.9...

    chisquare values are in counts (25MHz) so 42.9 counts = 1.7us. Those values look reasonable to me.

    I'm considering dropping old samples when the chisq value is high. This usually happens when...
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    This code is only built as an NTP (not PTP)...

    This code is only built as an NTP (not PTP) server. But I do have different code for the esp8266: https://github.com/ddrown/esp8266-clock

    It uses an NTP client to keep the local clock in sync, and...
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    I let this run for 5 days, and these are...

    I let this run for 5 days, and these are interesting results. I have two different Teensy 4.1 boards running this code.

    Temperature vs frequency over 256 second intervals:
    ...
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    I've added this line to updateTime:...

    I've added this line to updateTime:
    Serial.printf("PPS: %u %u %.2f\r\n", gpstime, lastPPS, tempmonGetTemp());

    I've collected this type of data in the past for other crystals, so I'd like to redo...
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    That looks good, thanks for trying it out!

    That looks good, thanks for trying it out!
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    Sure, the short term phase noise from the crystal...

    Sure, the short term phase noise from the crystal will be much lower than the GPS. But I think what is causing the larger offsets are the frequency change due to temperature changes. It would be...
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    The phase offsets happen at the same time as the...

    The phase offsets happen at the same time as the frequency changes, which has me thinking that my synchronization code needs some tweaking. I suspect PPS from a GPSDO wouldn't change much unless the...
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    The RMC message taking more than 1s would...

    The RMC message taking more than 1s would generate those lag error messages. The LAG messages can also be caused by no pps due to signal lock loss.

    I'm surprised you're getting B (bad time)...
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    Yes, I'm using the firmware defaults for the...

    Yes, I'm using the firmware defaults for the adafruit GPS, which is 9600 and no ZDA message. I'm also using an external antenna on a windowsill. Without an external antenna, I get bad reception.
    ...
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    I setup a second teensy with an Adafruit GPS. I...

    I setup a second teensy with an Adafruit GPS. I added the GPS_USES_RMC define to settings.h to support it. Originally I took the timestamp of the GPRMC message, but it would often be delayed into...
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    The columns from that output: T41 raw counter...

    The columns from that output:

    T41 raw counter value at PPS (25MHz)
    seconds offset between GPS PPS and virtual T41 clock (which is the first graph). The third graph is the measurement over the...
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    I wanted to use the teensy_loader_cli but the...

    I wanted to use the teensy_loader_cli but the soft reboot option wasn't working for me. I didn't dig very far into why it wasn't working, but I put together a workaround. If you send the character...
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    Teensy 4.1 NTP server

    I ported the embedded NTP stratum 1 server that I originally wrote for the stm32f407. It uses the 1588 ethernet hardware for RX and TX timestamps. I'm also using the 1588 event input capture to...
  17. Teensy 4.1 Ethernet and bandwidth delay product

    I went the osh park + digikey route to get an Ethernet connector for the Teensy 4.1, and I can report that it does work that way :)

    After getting the lwip_iperf example working, I had to tune lwip...
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    Looks good, thank you!

    Looks good, thank you!
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    I just noticed this too. D2 is EMC_25 and D1 is...

    I just noticed this too. D2 is EMC_25 and D1 is EMC_28, which are also on the schematic.
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    When sending to a windows machine, the bit-mapped...

    When sending to a windows machine, the bit-mapped keys above 0xFF (Search and Home in my case) work, but the bytecode ones (range 0x0-0xFF) do not work under windows (volume,...
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    sending USB HID page 0xC key codes above 0xFF

    Hello! I have a Teensy 2 using the Arduino environment. I want to use it to send key codes to an Android device. Specifically, I want to send keycode 0x223 (Android calls it KEYCODE_HOME) under the...
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