[Ovmsdev] V3 size and arrangement

Tom Parker tom at carrott.org
Sun Jun 11 09:21:43 HKT 2017

On 09/06/17 19:29, Mark Webb-Johnson wrote:
> Yep, that’s the idea now. We’ll probably make another couple of 
> ‘final’ boards to make sure all is ok. Check those, and if no problems 
> then hand make another twenty or so for developers. If no problems 
> reported, then make a large first production batch. Getting close now.

I would be keen to get a developer board.

The Leaf has 3 CAN buses (CAR, EV and Chademo) on the OBD2 connector and 
I really want to get the odometer value which isn't available on the EV 
bus we're on at the moment. I've also discovered that the 2016 model 
moved the TCU to the CAR bus, which may mean that we cannot do remote 
climate control on the EV bus -- the old messages on the EV bus don't 
work, I haven't had a chance to try them on the CAR bus.

Are you going to make new cables for the OBD2 port now or later? I can 
make one up for the Leaf and verify it works on all the buses. I haven't 
looked at what is on the Chademo bus, but watching the battery current 
and voltage reported on the EV bus as we currently do seems sufficient 
for knowing what is going on during DC Quick charging. Hence I feel we 
should supply a cable for the CAR and EV bus, leaving the 3rd bus for 
future expansion, for example to MitM a component by connecting it to 
the 3rd bus and having the OVMS gateway messages to the rest of the car, 
or the currently discussed OBD2 HUD or other dongle.

Can anyone recommend a source of low profile OBD2 plugs or a low profile 
extension cord that includes all the pins? I have plugs that are too big 
for use while driving and low profile extension cords that don't pass 
through all the pins :(

>> I hope there will be fewer bugs on the software side…
> At least those can be fixed by over-the-air software update. I’m more 
> worried about the bugs that need a soldering iron to squash.

We'll have to think very carefully about security for the code upload -- 
being careful not to implement risky functionality is moot when you can 
upload new code. The PIC's Harvard architecture and out of heap stack 
also made it pretty safe in the face of memory corruption bugs. Is the 
esp32 a von Neumann architecture? Is the stack in the same address space 
as the rest of system ram? Can pages be marked read only or no execute?

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