Re: [time-nuts] Ebay Huawei Ublox M8T Modules Warning

[Bob kb8tq]

Hi

Again, in case anybody else is interested ….

https://www.ebay.com/itm/ON-SALE-U-BLOX-ublox-LEA-M8T-0-10-HUAWEI-GPS-Timing-Module-Board/333778776570?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Turns out to be a bit more than what the listing implies. The parts I got
also came with a cable that goes from the round connector on the assembly
to an HDMI connector. That explains the HDMI connector pinout information
in the listing. 

The big ugly “plate” turns out to be easily removed from the assembly. 
That leaves you with a nice die cast box that is roughly 3 x 2.5 x 1”. It 
mounts to the plate via 4 small screws. 

Since you have a cable that fits the round connector, wiring it up to this or
that should be pretty easy.

Yes, the price keeps climbing ….

Bob

> On Jan 19, 2021, at 2:43 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> I don’t know if anybody else bought any of these or not. 
> 
>> On Jan 9, 2021, at 10:20 PM, Bob kb8tq > > wrote:
>> 
>> Hi
>> 
>> Just for the sake of listing all the variations:
>> 
>> https://www.ebay.com/itm/ON-SALE-U-BLOX-ublox-LEA-M8T-0-10-HUAWEI-GPS-Timing-Module-Board/333778776570?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
>>  
>> 
>> 
>> Is the M8T on what I would *guess* is the original board. Simply from 
>> looking at the picture I think 
>> you can guess pretty well what’s what on the board.  
>> 
>> Hint: If you buy quite a few …. errr … 10 … there s a pretty good chance 
>> that something more than 
>> 20% might get knocked off the price …. I bought a pretty large pile of stuff 
>> so it’s not clear if that 
>> had some impact on what offers got accepted …..
>> 
>> If that’s not your favorite RF connector on the board, there are SMA’s that 
>> likely fit in the same footprint.
>> 
>> Bob
> 
> If you did, the link now goes to a new auction (at a higher price). 
> That auction shows the board in it’s proper enclosure and provides a bit
> more ( but not quite all) information on the module. Since they are now 
> free shipping a much heavier gizmo, that might explain some of the 
> price increase. 
> 
> If you look at the box, the connector on that box most certainly is not an 
> HDMI connector. However it *does* tell you what signals are running around.
> You have the PPS out on RS-422. You also get the serial out of the module
> on another RS-422 pair. 
> 
> The clock in / clock out stuff … no idea. The EXT-INT pin on the M8T is 
> driven 
> by the 8051 CPU on the board. It’s a good bet that’s what those clocks are 
> getting to.
> 
> The TI switcher chip on the board has it’s input clamped at 20V. It puts out 
> 6.2V. No
> idea what the correct input is. It seemed to be very happy with the 15V I put 
> on it. 
> Pin 1 on J1 is power in. Pin 6 on J2 is ground. Ground also shows up on one 
> of 
> the mounting holes. The other pins on J2 appear to be 3 RS-422 pairs. 
> 
> All of the I/O lines are protected with clamp diodes. The antenna has 
> multiple 
> layers of protection. The debug pins on the C8051F320 come out to a connector
> that may or may not be populated on this or that board. There is a flash chip 
> on 
> the back side and an EEPROM on the front. If somebody was more ambitious 
> than I am, reprogramming the MCU to do fancy stuff might be possible. 
> 
> Fun !!!
> 
> Bob

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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Trent Piepho]

On Thu, Feb 4, 2021 at 4:09 PM Hal Murray  wrote:
> In case anybody isn't familiar with ARM SOC chips, they typically have a layer
> of muxes between the external pins and the internal I/O devices.  I don't know
> if the chip used in the Pi-4 works this way.  Quite likely.
>
>
> The system designer has to find a combination of mux settings that works for
> the application.  Leftover pins can be used as GPIO.  And the clocking is
> tangled up in there.

While true for many pins, usually quite a few are not muxed.  Those
deemed necessary for all designs or with specialized drivers.  So
typically there will be no mux for power pins, dram interface, xtal
inputs, and high speed differential data, like USB3, PCIe, SGMII, MIPI
CSI or DSI.  Or perhaps muxing between different high speed serial
interfaces.

It seems to be very common for ARM SoC chips to be designed to be
clocked by either an XTAL and a built in oscillator, or via an
external clock generator connected to the same pin.  But, I've never
seen a SoC where this pin could be muxed.

I've not seen one where the input clock frequency had much of a range.
It might be 24-26 MHz, but never 10 - 52 MHz.  At least documented.
But the clock is invariably an input to a programmable PLL or PLLs,
and those PLLs are likely programmable with a rather wider range of
multipliers and dividers than required for the limited documented
input frequency range.

One might have better luck with a chip from Ti or NXP, since, unlike
Broadcom, they have documentation on how their clocks and PLLs work.

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[time-nuts] Symmetricom uccm module

[paul swed]

Some years ago these modules were mentioned on Time-nuts. They were typical
Ebay stuff. I purchased one and really didn't do anything with it. Time
goes by. Was organizing stuff and had forgotten I even had it. Fired it up
and have to say its a pretty impressive little unit.
Like the fact that when warm it consumes 4 watts. LadyHeather works great
with it. All of this has been known and well documented. Just very nice to
see and most likely use as a small free standing GPSDO with a
reasonably fast warm up time. I also added a small battery for backup. The
advantage of this is it eliminates the automatic survey on power up that
takes some 3 hours.
Anyhow a very belated thanks for mentioning these units.
Regards
Paul
WB8TSL
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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Poul-Henning Kamp]

Hal Murray writes:
> 
> p...@phk.freebsd.dk said:
> > I dont know if the datasheet for the Rpi4 is available to check what the
> > requirements are, but you should probably expect to need some kind of PLL
> > chip to deliver a clean 54 MHz on the RPi4, locked to your external
> > frequency. 
>
> Plan B would be to avoid the 10=>54 PLL chip by reprogramming the software 
> that sets up the internal PLLs to run off 10 MHz rather than 54MHz.  That may 
> not be possible.  It depends on how the clocking inside the ARM chip is setup.

One of the big problems with the RPi family is that only a skeleton
datasheet has been made available - because: Qualcom magic sauce
recipe or similar verbiage..

I've heard a lot of gripes about precisely the clock circuits being
underdocumented, but I have deliberately stayed well clear of the
details.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Hal Murray]

p...@phk.freebsd.dk said:
> I dont know if the datasheet for the Rpi4 is available to check what the
> requirements are, but you should probably expect to need some kind of PLL
> chip to deliver a clean 54 MHz on the RPi4, locked to your external
> frequency. 

Plan B would be to avoid the 10=>54 PLL chip by reprogramming the software 
that sets up the internal PLLs to run off 10 MHz rather than 54MHz.  That may 
not be possible.  It depends on how the clocking inside the ARM chip is setup.

If you are lucky, you won't need to change the kernel.  If you are half-lucky, 
you have to make a few tweaks to the kernel software and rebuild.

-

In case anybody isn't familiar with ARM SOC chips, they typically have a layer 
of muxes between the external pins and the internal I/O devices.  I don't know 
if the chip used in the Pi-4 works this way.  Quite likely.

It's a chinese menu sort of deal, only more complicated.  If you get the beef 
from column A, you can't get the chicken from column B.

The basic idea is that there are more I/O devices on the chip than there are 
pins.  After reset, all the pins are setup as GPIO input so they don't 
accidentally drive an input pin.  There is a mux in front of each input signal 
to an I/O device that picks the signal from one of several pins.  There is a 
mux on the output side of each pin that selects from an output of several I/O 
devices.

The system designer has to find a combination of mux settings that works for 
the application.  Leftover pins can be used as GPIO.  And the clocking is 
tangled up in there.


-- 
These are my opinions.  I hate spam.




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[time-nuts] TimeHat setup & walkthrough video

[John Miller via time-nuts]

Hello again everyone!
I wanted to send out another message regarding the TimeHat to let you all know 
that I made a short video that includes some more information about it, 
including what all you get and how to set it up and use it. Even if you don’t 
get one of these modules from me it may help inspire your own projects!

https://www.youtube.com/watch?v=VrDRAVy_bg4 


Thanks,
John M.
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[time-nuts] LEA M8T boards

[Matthias Welwarsky]

Dear all,

When the availability of some surplus Ublox M8T modules was announced, I 
ordered a few of them and started designing a small breakout board for them. 
The design meanwhile had a little cool-down period and matured somewhat. Since 
I realized that for most people it can be quite daunting to un-solder the LEA 
modules from the PCB cut-off they come delivered on, I ordered a few more of 
them and had a small batch of the breakout boards assembled as well.

So, in a few days I'll have about 22 LEA modules and 25 breakout boards 
waiting to be mated. Since the LEA modules are all pulls (or rather cut-outs) 
and are still on their carrier PCBs, I'm not sure what the final yield will 
be.

If anyone's interested in buying a module + breakout board (assembled and 
tested), drop me an email off-list.

Best regards,
Matthias



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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Matthias Welwarsky]

On Donnerstag, 4. Februar 2021 11:20:23 CET Avamander 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-osci
> llator-on-a-rpi-2-3

Feeding a 10MHz (suitably conditioned) clock signal directly from a Rb into a 
Beaglebone Black's external clock input (available on the extension header) 
and adding a small driver module to use a timer driven by this external clock 
as system clocksource is _way_ easier.

Just my €0.02

BR,
Matthias



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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[David Taylor via time-nuts]

On 04/02/2021 10:20, Avamander 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


I would likely use one of these:


http://www.leobodnar.com/shop/index.php?main_page=product_info_id=301

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv

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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[ASSI]

Avamander wrote:
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard?

The same things as replacing the XTAL on an RPi 1…3 I'd guess.  So, you need 
to remove the XTAL (hot air rework station), figure out which pin you need to 
feed the external clock into (the "return from XTAL" path), and actually 
create a rubidium stabilized 54MHz (using a clock synthesizer like the SiLabs 
SI53xx series, for which you can get breakout boards rather easily).

> An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?

Not much, see above.

However you'll probably find that it really is overkill and you can get much 
of the same end result more easily or much cheaper.  For instance a good OCXO 
or even TCXO would already get you the sort of stability that the other 
sources of timing uncertainty produced by the whole SoC / OS interaction start 
to dominate.  I haven't gotten myself a Pi4 yet, but I expect that self-
ovenization would still work more or less the same as with the earlier models, 
so you might not even need to touch the XTAL.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds




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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Poul-Henning Kamp]

Avamander writes:

> 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?

This trick has gotten a lot harder over the decades.

Higher and higher PLL ratios in the chips means they demand more of their clock 
signal.

I dont know if the datasheet for the Rpi4 is available to check
what the requirements are, but you should probably expect to need
some kind of PLL chip to deliver a clean 54 MHz on the RPi4, locked
to your external frequency.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

> On Feb 4, 2021, at 11:37 AM, Avamander  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  > 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  > > 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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Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Avamander]

> 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?

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  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  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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>
>
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Re: [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  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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[time-nuts] Raspberry Pi 4 oscillator replacement

[Avamander]

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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