[time-nuts] Ublox 8T - breakout board

[Matthias Welwarsky]

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

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