[time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

Pretty basic approach:

1) Get a Rb standard. 

2) Grab any of the various conversion chips to take the 10 MHz to 54
(= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
and pull the 54 off of it. (Yes, the chip needs to be programmed and 
there will be various bits and pieces connected to it)

3) Rip the oscillator (or crystal) off the RPi board. 

4) Figure out which pin is the drive to the crystal and which is the return.
(or which is the output if it’s an oscillator)

5) Wire the 54 MHz into the return / osc out pin. 

6) Power it all up off of a common supply ( = power the conversion 
chip off the RPi’s regulator.

Yes there is a lot of research needed to complete all of that. 

When done you would need to figure out how to ( … if you can ) disable
the spread spectrum stuff on the clock. You still would be stuck with
the normal issues related to clock frequency stepping ( turbo mode …).
How much of that actually gets you on an RPi 4 … who knows. 

Bob

> On Feb 4, 2021, at 5:20 AM, Avamander <avamander at gmail.com> wrote:
> 
> Hi,
> 
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?
> 
> Here's where I got my inspiration from, someone replacing the oscillator on
> a Pi 3 with a TXCO:
> https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
> 
> 
> Yours sincerely,
> Avamander
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