[Ovmsdev] Prototyping expansion board

[Mark Webb-Johnson]

Craig,

What is the reason to use newer/better cell modems? I presume you are talking about 4G, but given that 3G is currently well supported, and we have a 115200bps link to the modem, what is the purpose?

Our modem board design does follow SIMCOM’s recommendations for layout compatibility, and you may be able to find a 4G SIMCOM module that is a drop-in replacement for the SIM5360 we use. We did make a prototype for the 7xxx series 4G NB iot chips, but that was a different size and the layout was quite different. Perhaps the pure LTE 7100/7500/7600 would work better?

The modem board is relatively complex and tightly packed. For example, it requires it’s own power supply circuitry as it doesn’t operate from either 3.3v or 5.0v (I think it uses 3.6v, but can’t remember exactly). We don’t use BGA, but it is surface mount technology. Overall, it is probably easier to just take our schematics and board layouts and make your own.

The J1850 may be simpler. You could use one of these new prototyping boards to implement it relatively easily. You could also do it externally off the DA26 port, but the I/O is more flexible in the internal expansion area.

Regards, Mark.

> On 18 Apr 2019, at 5:03 AM, Craig Leres <leres at xse.com> wrote:
> 
> Both I and my friend (who has a roadster) would like to use the newer/better cell modems. And the extra cost of the module that causes you guys to choose not to mass produce and sell isn't a barrier for us.
> 
> If bare modem boards were available how hard would it be to populate some with newer cell modems? If everything has exposed pins I'm sure I could do it (I've built a few small boards of my own design and have a stereo microscope). But if there are any BGA involved I wouldn't want to attempt it. (Looking at the pictures on fasttech.com I don't think this is will be a problem.)
> 
> And at some point I also want to use ovms in my J1850/Class 2 C6 Corvette. I'm very familiar with the J1850 side. But I don't know which approach would be best: either adding a custom board internally or making an external j1850 to can bridge (could it plug into the HUD port?)
> 
> 		Craig