[time-nuts] Ublox 8T - breakout board

[Peter Reilley]

May I suggest not populating the DIP header.   If it is put on top of
the board then that prevents it from being plugged into another
board, the SMA connectors get in the way.

If you want to use the board separately then the DIP can be put on
the top.   If you want to plug your board into another board then
you would put the DIP header on the bottom.

DIP headers are easy to solder in but hard to remove.   Let the
customer put it in as they may choose.

Pete.

On 12/15/2020 7:57 AM, Matthias Welwarsky wrote:
> Time-nuts,
>
> I've updated the repository on github with the latest design files. The
> breakout board is now final as far as I'm concerned.
>
> I managed to implement all the requested features, this includes the backup
> battery and also the buffered PPS output with SMA footprint.
>
> Next step on my side will be to order a small batch of PCBs. There's not much
> on them and I guess I will end up with around 25€ for 5 boards fully
> assembled, shipping not included.
>
> I eventually removed the I2C pull-ups again, thanks to Patrick Tudor for the
> hint. The footprints are still there, I only removed them from the BOM.
>
> Schematic and a screenshot of the top and bottom sides attached.
>
> BR,
> Matthias
>
> On Montag, 14. Dezember 2020 10:16:32 CET Matthias Welwarsky wrote:
>> Dear all,
>>
>> I've received quite a number of emails with feedback, thank you very much
>> for your interest and participation. I'll not respond to the individual
>> mails so here's a summary:
>>
>> * Will the design files be public: Yes, you can find a Work-In-Progress
>> state of the complete development project here:
>> https://github.com/thinkfat/ublox-breakout. It's a KiCAD 5 project, but
>> there's a "fab" folder that contains Gerber files and BOM and CPL files for
>> JLCPCB SMT. THIS IS NOT THE FINAL DESIGN REVISION!
>>
>> * Thanks for the LDO suggestion, I'll have a look at them.
>>
>> * Buffered PPS output + SMA footprint: While it may not appear so, the board
>> is quite densely populated and SMA connectors are rather large. I'm
>> checking if I can afford to make the board a bit larger. Thanks for
>> suggesting the 74HC244.
>>
>> * Symmetric mounting holes: I reshuffled the layout a bit, that will work
>> out fine.
>>
>> * Backup battery: I consider that not a priority for a timing receiver.
>> However: a Keystone mounting bracket for a CR1220 battery would fit on the
>> backside, but I need to find out how to make that optional, the backup
>> supply pin must be connected to the main power supply if not equipped.
>> Maybe a couple of diodes are sufficient to prevent back-feeding the battery
>> from the main 3.3V.
>>
>> * Pull-Up resistors for the I2C: OK
>>
>> * D_SEL on the pin header: OK
>>
>> Attached a screenshot of the current layout.
>>
>> BR,
>> Matthias
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.