[time-nuts] Frequency Counter using OCXO and MCU

cfo xnews3 at luna.dyndns.dk
Wed Mar 12 12:10:48 EDT 2014

On Wed, 12 Mar 2014 11:48:04 -0400, d0ct0r wrote:

> LCD connected to the same MCU. And it has relation to the core clock
> too. So, nothing on LCD before I reset entire MCU. I think initial
> incorrect core clock reading cause a lot of issues. Probably my only
> option will be to implement some external relay and timer to turn on MCU
> few seconds after OCXO. Or may be to put 10Mhz oscillator to PCB and
> connect OCXO output in parallel to it (not sure if its good idea or it
> will works).

You could start the MCU up on the internal clock , write to the lcd , 
wait 5 sec. And then switch to the external clock.

Is the Ext clock input on the STM fed directly from the OCXO ?
Can the STM handle the OCXO voltage swing ?

If you have a conditioning circuit betewwn the OCXO and the STM , i'd 
like to see it. As i have the need for one , trying to interface a 5v OCXO 
to a NXP 1114 Arm , that wants max 1.8v in the clockinput.


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