[time-nuts] WWVB teensy BPSK early experiments

[jimlux]

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.


> 
> Bob
> 
>> On Oct 31, 2020, at 7:17 PM, jimlux <jimlux at 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)
>>
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