Alternative Gnuk token board design

Rigas, Evangelos e.rigas at cranfield.ac.uk
Mon Mar 25 11:57:21 CET 2019


Hi Mike,

I had a look on weblight, the trick with diodes is realy nice.
As for the ProtoProg, I had a similar design in mind.

Thanks, for the links.

Evangelos

On Thu, 2019-03-21 at 16:18 -0700, Mike Tsao wrote:
Evangelos:

I did a project a few years ago that has a similar form factor to yours: https://github.com/sowbug/weblight

A notable difference is that the Weblight board can be inserted in either top or bottom orientation in the Type A slot, a little like Type C but through the magic of diodes rather than symmetric design of the female connector. This was more important for my project because it had a visual component to it, but I'm sure users would appreciate the flexibility. Plus you're already solder-masking both sides of the PCB, so it's no additional manufacturing cost except for the diodes.

As you can see in the board order I did<https://github.com/sowbug/weblight/blob/master/hardware/mfg/production/1.0/pcbcart-pcb-order-160930.pdf>, I chose ENIG finish with 2.0mm thickness. We ended up ordering another 1,000 in addition to that order, and we've never had a complaint about proper fit in USB ports.

I also took the ProtoProg<http://protofusion.org/wordpress/2013/05/open-hardware-pogo-pin-programmer/> concept for the pogo programming, ordering the PCBs from OSH Park<https://oshpark.com/shared_projects/fqvxyzoH> (I'm in the US, so that was a perfect option for me). That tool is AVR-based, so it's not applicable to your project except to the extent you might want to copy that design and alter it for STM32 programming.

Mike

On Thu, Mar 21, 2019 at 7:37 AM Rigas, Evangelos <e.rigas at cranfield.ac.uk<mailto:e.rigas at cranfield.ac.uk>> wrote:
On Thu, 2019-03-21 at 13:43 +0100, Peter Lebbing wrote:
> And a nice touch to include a design for the pogo pins.

Thanks Peter.
I plan to design a PCB (some sort of a jig) for programming. That way
it will be easier to make, instead of relying on expensive 3D printers.

As for the gold platting of the connector, you are right. That is why I
ordered the PCB with ENIG (Immersion Gold).
Is not the same quality as hard gold, but an order of magnitude
cheaper.

In addition, ENIG offers better planarity on the exposed pads which
helps with SMD soldering; compared to the default hot air solder
leveling (HASL) process.

Cheers,

Evangelos
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