[onerng talk] The world's (other) most secure TRNG

[Bill Cox]

On Sat, Oct 11, 2014 at 10:18 PM, Paul Campbell <paul at taniwha.com> wrote:

> On Sat, 11 Oct 2014 21:55:54 Bill Cox wrote:
> > It's very low-speed, but I think secure.  I'm sure anyone with any
> > experience could tell me the 100 things I got wrong on this tiny
> design.  I
> > welcome such feedback.
>
> so some minor suggestions:
>
> - the circuit board etch USB pug  idea is cheap and cool - but it's is
> terribly unreliable (everyone with one of my programmers that use this
> rightly
> complains) - I've switched to proper plugs (SMT plus 2 thru holes) - for
> what
> you're doing you need to tape your board out in 2mm thick board (2.2-2.4 if
> you can) with ENIG plating, and even then you'll usually need a bit of
> masking
> tape on the back of the connector to stop it falling out of some sockets
>
> - I prefer to lay down ground planes on both sides and have Eagle take
> care of
> them- in Eagle create a polygon on each side then name it 'gnd' the click
> the
> flow (ratsnest) button - personally for my RNG there are NO traces on the
> bottom under the analog portion, it's all shield - drop vias where
> possible to
> stitch the two planes, and drop vias next to ground pins on ICs
>
> (your analog world may require more of an audio approach to grounding - you
> can create split ground planes pretty easily using this technique)
>
> - you can likely get away with much much smaller vias (check the eagle
> layout
> file you got from your board house - I typically use .35mm) - ideally you
> want
> them small enough that they get tented with solder mask
>
> - looks you probably don't have the layers on that handle component
> restriction layers - that's OK for something you're planning on assembling
> by
> hand - a P&P machine might run into trouble (just a guess from eyeballing
> it)
>
>         Paul
>
> --
>
> View topic http://lists.onerng.info/r/topic/5PgQzXiqfCdbNqpS0CA7PL
>
> Leave group mailto:onerng-talk at lists.onerng.info?Subject=unsubscribe
>
> Start groups http://OnlineGroups.net
>

Thanks for the tips.  I made the changes you suggested, except the
component restriction layer.  Is that just the tDocu layer were we draw the
outline of the parts?

Thanks,
Bill
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ourshack.com/pipermail/discuss/attachments/20141012/2d653a6c/attachment.html>