Hi
> On Oct 31, 2020, at 9:45 PM, jimlux <jim...@earthlink.net> wrote: > > On 10/31/20 4:46 PM, Bob kb8tq wrote: >> Hi >> Looking at the data sheet for the MCU, they really do want 24 MHz and that’s >> about it. I suspect you would >> do better to take your 10 MHz OCXO and run it into one of the frequency >> converter chips to get the 24. >> Then feed that into the board. One more chip, but you now don’t have a bunch >> of stuff to hack up. > > > Yeah.. you can spin the dial on the signal generator and move the frequency > up and down, but.... Nothing is guaranteed to work right. Who knows what > sort of little DPLLs are on that chip that have narrow ranges, etc. > > This experiment was with a Teensy 3.1 - I had a lot of them, so I wasn't > afraid to hack it up. Your OCXO will have a much narrower tuning range at the extreme’s of it’s EFC than the tolerance on the typical crystal. The MCU PLL’s will run over the OCXO tune range …. Bob > > >> Bob >>> On Oct 31, 2020, at 7:17 PM, jimlux <jim...@earthlink.net> wrote: >>> >>> On 10/31/20 11:42 AM, Bob kb8tq wrote: >>>> Hi >>>> …..errr….. >>>> Can you pull the clock oscillator off the Teensy board? (Yes, the soldering >>>> iron would be involved). >>>> Will the clock input to the MCU accept something like 10 MHz? If so solder >>>> on a cable …. >>>> At that point whatever the Teeny does is locked to the 10 MHz. If that >>>> comes >>>> from one of the $3 eBay OCXO’s, steer that with a DAC output … now you >>>> have a WWVB GPSDO. >>>> Indeed, if the Teensy needs 28 MHz, then the OCXO will not be quite as >>>> cheap. >>>> Bob >>> >>> I've tried this - It will run just fine, but *all the UART and USB speeds >>> change*. So, basically, the USB stops working, and you need to set your >>> serial port to something like 112.8 * 10/28 (and it takes a bit of fiddling >>> to get it to work right).. I sort of cheated, and switched back and forth >>> - signal generator to 28MHz, load and debug software, start it, then switch >>> generator to 10 MHz. >>> >>> And of course, all the functions that are time based, like delay() are the >>> wrong length. >>> >>> One could probably figure out a relatively few patches to the Teensyduino >>> code base that would fix all this (clock rate is a variable - you can run >>> the teensy at multiple clock rates, even with the same crystal) >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
