Anelok: the journey towards V1

Felix sucotronic at gmail.com
Mon Jun 2 01:54:26 EDT 2014


That last iteration its incredible! Yeah, it has lot of via, but as long as
it doesn't interfere with RF part I also think is a nice layout.

One question about the capacitive sensor, does it works with the thick
player of plastic that will be the case? I know there are some capacitive
sensors able to work as far as 1cm, but don't know how this chip will
perform :P


On Mon, Jun 2, 2014 at 4:16 AM, Werner Almesberger <werner at almesberger.net>
wrote:

> I'm working towards the V1 board which will, among smaller changes,
> replace the wheel with a capacitive sensor and the AT86RF231 with the
> CC2543.
>
> I tried a few different component placements for this. An overview
> drawing can be found here:
> http://downloads.qi-hardware.com/people/werner/anelok/tmp/v1s.pdf
>
>
> First, I tried the approach where the CC2543 helps the KL26 with its
> GPIOs, so that a smaller package with fewer pins can be used with the
> KL26. This is in the branch "puppet". The memory card would be
> ejected into the battery compartment.
>
> This is nice and compact, but routing the control signals from the RF
> SoC promises to be difficult. I also had second thoughts about having
> the two chips interact so tightly, especially since the CC2543 would
> not only have to handle control outputs (power on, etc.), but also
> some interrupt lines.
>
>
> I then tried to see what would happen if I just adapted the version 0
> design. I also gave the KL26 its own crystal (more about this in a
> separate post).
>
> A first try - branch "large" - looked somewhat promising but I ended
> up with very long traces and a few problems with the pin assignment.
>
>
> Next was a more radical attempt to put all major components on the
> top layer, to avoid vias. This is in the "coplanar" branch. It looked
> pretty good, with one problem: with components as tall as about 2-2.5
> mm on the top, the FPC of the OLED would get bent quite a bit.
>
> I also moved the battery to the center, to allow for better holders.
> More about this later. Last but not least, I tentatively added the
> "hard" rfkill switch.
>
> I almost made this board, but then I chickened out, fearing it might
> become too much of an FPC killer.
>
>
> The next attempt, "split", moved everything but the OLED FPC and the
> LED to the bottom. I could make it all fit but had to share some
> signals, had other pin assignments that were far from optimal, and
> the traces to the capacitive sensor took a rather epic journey.
>
> Naw, too many concessions.
>
>
> Then I decided to face my fears and made a design that wouldn't try
> to avoid vias. It's in the "dftv" branch, "Don't Fear The Vias".
>
> This one places the large chips on the top layer and tall components
> (USB, switch, memory card holder) on the bottom. It also places the
> memory card such that it ejects into the battery compartment again.
>
> This worked surprisingly well and I could assign all the signals to
> "good" pins and keep delicate traces short. Since the card holder
> eats up a lot of space, there was very little room for the USB side,
> which also has some of the power supply circuit. Things got too
> crowded with the OLED FPC in the same area, so I flipped the OLED and
> the FPC now connects at the top edge.
>
>
> I think this looks good enough to try. I therefore merged "dftv" into
> the master branch. If anyone wants to have a look, the schematics are
> here:
>
> http://downloads.qi-hardware.com/people/werner/anelok/tmp/anelok-20140601.pdf
>
> The layout is here:
>
> http://downloads.qi-hardware.com/people/werner/anelok/tmp/anelok-20140601.png
>
>
> More details about the various designs can be found in
> https://gitorious.org/anelok/anelok/source/hw/NOTES
>
> - Werner
>
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-- 
Felix
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