[Ovmsdev] V3 size and arrangement

[Mark Webb-Johnson]

I'm still trying to work out the stackable/side-by-side issue.

The thing I didn't like with the stackable option is the height (assuming each expansion module is also stackable). Every time I look at Arduino / Raspberry / etc, I think it is too tall. My problem is that top-most stackable connector that is _always_ empty. I know why it is there - but it just increases the height for the enclosure.

I am thinking that perhaps there is a way out. 

What if we used a stackable design, but just have the modem modules non-stackable? The modem always goes on top. That way, the height of a normal system (without expansion modules other than the modem) is mostly unaffected. If an expansion module is required, then it must be stackable and placed between the main board and the modem. The non-stackable modem always on top. So for the 5% of users who use in-the-box expansion, they need a bigger case, but the 95% of other users can go with something slimmer.

Kind of like this: Base board on the bottom, stackable expansion boards in the middle, and non-stackable modem board on top. The top picture shows the 5% case (with stackable expansion module sandwiched), the bottom picture shows the 95% case (with just base and modem).

Size wise, we could go with something more like an Aurduido Due. Wider than OVMS v2, but about the same height and depth.

Thoughts?

Regards, Mark.

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> On 19 May 2017, at 2:23 PM, Mark Webb-Johnson <mark at webb-johnson.net> wrote:
> 
> I've got the first OVMS v3 development board in my hands now. The components seem fine, and I'm finalizing the QC program that checks everything to make sure all is ok. 16MB flash with OTA capability, Wifi, Bluetooth, 3xCAN bus, lots of GPIO, switched 12V, power by USB/12V, SD card reader/writer, optional 2G/3G/4G modem (with GPS), two expansion slots, USB, and an external expansion connector - all look good.
> 
> Both 3G and 4G development expansion boards are also being made now, and I should have those next week.
> 
> But, having seen it and held it, I'm now having second thoughts about the layout. As you can see from the attached pictures, the expansion slots are each about 60mm x 45mm. Putting two of those on the board makes it about 9.5cm x 9.5cm square. Height will be similar (a little bit taller) than the current OVMS v2. This is a first draft run only, just to confirm the components, but as you can see there is quite a lot of blank space and traces for the two expansion slots. That, and the sheer number of connectors we have, dominate the board. Let's call this arrangement (A).
> 
> There was an alternative arrangement that I considered a while back. That would be to have just one expansion slot, but use stackable connectors (so multiple boards could be piggybacked on each other). In that arrangement, the expansion slot could be either vertical or horizontal, with a vertical arrangement being close in size to the existing OVMS v2 (but the height would need to be much taller to accommodate the piggybacked expansion boards). Let's call this arrangement (B).
> 
> It doesn't change the wiring. Just the size and arrangement of components on the board, as well as the box housing this all. (A) ends up with a 1" wider+taller box of about the same thickness, while (B) ends up with a box about the same width and height, but significantly thicker. To me, it seems that (A) is more automotive, and (B) more hobbyist.
> 
> What do people think?
> 
> In the meantime, on with development (now that at last I have a target in my hands).
> 
> Mark
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