[Ovmsdev] V3 size and arrangement

HONDA S-2000 s2000 at audiobanshee.com
Sat May 20 12:47:57 HKT 2017

I'm a bit of an odd customer. I have both the V1 and V2, but have never activated a SIM for either of them. My interest is in discovering what is on the CAN bus, and having a familiar programming platform like the PIC as a way to investigate. I'm perfectly willing to use on-board storage and read out the data manually rather than hassle with activation, accounts, and periodic payments.

For me, the main advantage of the V3 is the second CAN bus. I imagine that adding a second CAN connector necessarily makes the V3 larger than the V1 & V2, but it's worth it for that feature. I'm personally less interested in having two expansion boards, especially if the second expansion makes the case significantly larger than it would be just for the second CAN bus connector.

Then again, I may be the only customer not interested in the SIM communications abilities. If I ever get a stable firmware and stop investigating, then I probably would jump on a SIM and enable remote data gathering.

My application is the Tesla Roadster, so I have similar size constraints as Stephen and others.


p.s. The upgrade from PIC to ARM is a welcome advantage. I'm familiar enough with PIC to not count that processor as much of a negative, but ARM is a solid positive feature. I'm currently working on a Texas Instruments (Stellaris) Cortex-M4 for another design project.

On May 18, 2017, at 11:23 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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