[time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

> On Feb 4, 2021, at 11:37 AM, Avamander <avamander at gmail.com> wrote:
> 
> > 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)
> 
> Do you have any recommendations as to which chip would let me achieve this?

Only because you can get it as a pre-assembled dev board:

https://www.silabs.com/timing/clock-generators/cmos/device.si5350c-gm1

at a semi-rational price. 

Most modern chips are a bit difficult to deal with. That makes finding a
dev board important. If you are set up to layout and assemble SMT PCB’s
then there are a lot of choices ( as in several hundred devices). 

Bob


> 
> In any case, thanks for the help. I will try and document the process when I start it and share it here, might be interesting for some.
> 
> On Thu, Feb 4, 2021 at 5:15 PM Bob kb8tq <kb8tq at n1k.org <mailto:kb8tq at n1k.org>> wrote:
> 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 <mailto: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 <https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3>
> > 
> > 
> > Yours sincerely,
> > Avamander
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