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 <[email protected]> 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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