[time-nuts] Ublox 8T

Wed Dec 9 22:58:51 UTC 2020

Hi

What you want around the uBlox depends a lot on what you are trying to do. 

These days, putting an MCU directly on this or that is a pretty cheap option.
(very much so if you are using JLPCB). 

Do you isolate / buffer this or that?  Full RS-232 I/O adds a chip and a few parts. 

Do you regulate this and that on the board? Is the antenna supply independent of
the module? Do you have full sensing on the antenna supply? 

For some, part of the mix is a delay chip to handle the sawtooth correction. Very 
much a “that depends” sort of thing. 

Do you put a counter / TDC of some sort on the board to do a compare to an external 
PPS? (At this point this list just about has a full GPSDO buried in it ….)

Lots of choices and lots of directions you could go.

One of the reasons I really like JLPCB is that you can do up 5 of a board like this, 
with a lot of parts populated and still not have spent $100 (delivered ….).  As long 
as you have confidence in the footprints, the risk is pretty small. 

One note: JLPCB is the only “fab + assembly” outfit I’ve tried. Their boards are 
no better / no worse than a lot of other board fab outfits. I have no idea how they
compare to other assembly houses. My selection criteria: “ are they the cheapest
I can find?” :) 

Bob

> On Dec 9, 2020, at 5:35 PM, Matthias Welwarsky <time-nuts at welwarsky.de> wrote:
> 
> On Mittwoch, 9. Dezember 2020 21:46:25 CET Philip Gladstone wrote:
>> I have used the assembly service from jlcpcb a few times for small runs --
>> it is absurdly cheap *if* you are using common surface mount components and
>> cheap for the less common ones. I then hand solder the connectors on when I
>> get the boards.
> 
> That's what I typically do as well. But you don't need a lot of support 
> components for a M8T, it's almost not worth it. Effectively, you have
> 
> 3 parts for the antenna power feed-in
> 1 decoupling cap for the module itself
> 1 resistor or ferrite bead for each signal you need to break out
> 3(4) parts for the power supply (LDO)
> 
> USB needs just a few more parts, two resistors, a protection chip and a 
> receptacle.
> 
> 
>> 
>> Philip
>> 
>> On Wed, Dec 9, 2020 at 3:27 PM Matthias Welwarsky <time-nuts at welwarsky.de>
>> 
>> wrote:
>>> On Mittwoch, 9. Dezember 2020 14:57:55 CET Bob kb8tq wrote:
>>>> Hi
>>>> 
>>>> I think the key point is:
>>>> 
>>>> *IF* somebody wants to do a layout using the M8T, Bert already *has* a
>>>> “known good” PCB layout footprint in his inventory of useful stuff.
>>>> Since
>>>> the uBlox is a really odd part, you aren’t going to find that footprint
>>>> built into the standard layout programs.
>>> 
>>> I have a known-good footprint and symbol for KiCAD, if anyone is
>>> interested. I
>>> also have KiCAD project for a small breakout board. It's not too
>>> featureful,
>>> no antenna power switching or monitoring, no support for antenna power
>>> other
>>> than from the built-in LDO. However, it has been successfully used in a
>>> GPSDO
>>> project. All components are hobbyist-friendly 0805, except for a LDO with
>>> SOT-23-5 footprint.
>>> 
>>>> Bob
>>>> 
>>>>> On Dec 8, 2020, at 6:26 PM, Bill Notfaded <notfaded1 at gmail.com> wrote:
>>>>> 
>>>>> That's a really old board though.  An 8 series isn't pin compatible
>>> 
>>> with
>>> 
>>>>> say LEA-6T is it?  The picture had a 5 series in it.
>>>>> 
>>>>> Could you use something like this?
>>> 
>>> https://github.com/PaulZC/NEO-M8T_GNSS_FeatherWing/blob/master/LEARN.md
>>> 
>>>>> Bill
>>>>> 
>>>>> On Tue, Dec 8, 2020, 10:30 AM Gregory Beat via time-nuts <
>>>>> 
>>>>> time-nuts at lists.febo.com> wrote:
>>>>>> There are various Breakout (bare) Boards for the uBlox modules posted
>>> 
>>> on
>>> 
>>>>>> Internet.
>>>>>> SparkFun has carried them, in the past, and sometimes sold the bare
>>>>>> boards
>>>>>> without the uBlox module.
>>>>>> https://www.sparkfun.com/products/15005
>>>>>> 
>>>>>> StuartsProjects (Stuart Robinson, Cardiff, UK) has a bare board for
>>> 
>>> the
>>> 
>>>>>> Ublox MAX M8Q module.  Sold on Tindie, used in high-altitude balloon
>>>>>> projects.
>>> 
>>> https://www.tindie.com/products/stuartsprojects/ublox-max-8mq-gps-breakou
>>> 
>>>>>> t-board-x-2/
>>>>>> 
>>>>>> Contact Limor “Ladyada” Fried at Adafruit, she might have bare boards
>>> 
>>> OR
>>> 
>>>>>> Gerbers for earlier or future products.
>>>>>> https://www.adafruit.com/?q=gps+breakout&p=1&sort=BestMatch
>>>>>> 
>>>>>> Dan Watson designed one, for the 6-series five years ago.
>>>>>> He sometimes posted Gerber files.
>>> 
>>> http://syncchannel.blogspot.com/2015/09/a-nearly-perfect-u-blox-gps-break
>>> 
>>>>>> out.html
>>>>>> 
>>>>>> greg
>>>>>> w9gb
>>>>>> ==
>>>>>> Date: Mon, 7 Dec 2020 09:47:55 -0500
>>>>>> From: paul swed <paulswedb at gmail.com>
>>>>>> To: Discussion of precise time and frequency
>>>>>> 
>>>>>>  measurement <time-nuts at lists.febo.com>
>>>>>> 
>>>>>> Subject: Re: [time-nuts] Ublox 8T
>>>>>> 
>>>>>> Bert Very attractive price. They appear to be on a cut out circuit
>>> 
>>> board.
>>> 
>>>>>> How are you connecting to them please?
>>>>>> Regards
>>>>>> Paul.
>>>>>> WB8TSL
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>>>>> 
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