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  • JBeale's Avatar
    08-06-2020, 06:02 AM
    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,...
    35 replies | 675 view(s)
  • JBeale's Avatar
    08-02-2020, 06:35 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    08-01-2020, 04:13 PM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-30-2020, 06:07 PM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-30-2020, 07:18 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-30-2020, 05:41 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-30-2020, 04:10 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-29-2020, 01:52 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-29-2020, 01:30 AM
    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...
    7 replies | 294 view(s)
  • JBeale's Avatar
    07-17-2020, 04:29 AM
    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...
    29 replies | 1259 view(s)
  • JBeale's Avatar
    07-17-2020, 02:32 AM
    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:...
    29 replies | 1259 view(s)
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10-25-2012