[Ovmsdev] OVMS V2.5 production / Renault Zoe support

Tue May 9 08:21:40 HKT 2017

Greg,

> But, for our (OVMS) purposes, do we know of any cars that need
> connection to more than two?

We are getting by at the moment with connection to just one. More than one is a ‘nice to have’. Only having one may limit what we can do. It is hard to answer the question as up until now we’ve only had one CAN bus (OVMS v1 and v2) so we’ve never really looked hard at what a second (or third) bus would give us.

I know that for the Nissan Leaf, there is a bridge and we can poll across the two buses - but that is klunky and slow (a direct connection would be much easier and provide greater control). So far that car we sit on the EV bus and poll across for vehicle things like speed.

For Tesla Roadster, we are unable to pre-cool / pre-heat the car as the instrumentation bus we are on doesn’t have that capability. The HVAC bus may (but we haven’t tried).

> Currently, OVMS v2 only connects to one CAN bus, right?

Yes.

> are there any cars that OVMS needs to
> support, that don't already support these dongles directly on the OBDII
> port, and that need OVMS to connect to more than two CAN busses in order
> to function?

I think two for vehicle control should be sufficient. I added the third for this idea of external display, and because it was just a couple of bucks more and 2 GPIO pins.

The other option that multiple buses gives us is to physically break the CAN bus into two and bridge it programatically. Some people have done that for both reverse-engineering as well as message spoofing / modification purposes.

Regards, Mark.

> On 9 May 2017, at 8:10 AM, Greg D. <gregd2350 at gmail.com> wrote:
> 
> Right.  As it should be.
> 
> But, for our (OVMS) purposes, do we know of any cars that need
> connection to more than two?  I'm guessing is this more of a matter of
> future-proofing the design (which is a really good idea!).  Currently,
> OVMS v2 only connects to one CAN bus, right?
> 
> I guess what I am wondering is, are there any cars that OVMS needs to
> support, that don't already support these dongles directly on the OBDII
> port, and that need OVMS to connect to more than two CAN busses in order
> to function?  Hopefully that intersection is empty...  If not, then
> there would need either be some multiplexing (risky), or an either-or of
> functionality (undesirable).
> 
> For my own purposes I'm focused on the Roadster, to which I believe OVMS
> only needs a connection to CAN0.  Yes?  (This is from the discussion
> here:  https://teslamotorsclub.com/tmc/posts/52337/ )
> 
> Greg
> 
> 
> Mark Webb-Johnson wrote:
>> On many modern cars there are multiple CAN buses used for different things. The approach is to separate different parts of the car onto different buses.
>> 
>> For example, the Tesla Roadster has three CAN buses, the Nissan Leaf has two, and the Tesla Model S and X have at least four.
>> 
>> It is helpful for OVMS to be able to connect to multiple CAN buses to be able to have more functionality (control parts of the car not directly connected to a single CAN bus).
>> 
>> Regards, Mark
>> 
>>> On 9 May 2017, at 6:41 AM, Greg D. <gregd2350 at gmail.com> wrote:
>>> 
>>> Hi Mark,
>>> 
>>> I'm curious why there would be an issue with using one of the three CAN
>>> bus ports for a down-stream device?  Do some cars require connecting to
>>> all of them for normal operation?  What else would they be used for?
>>> 
>>> Thanks,
>>> 
>>> Greg
>>> 
>>> 
>>> Mark Webb-Johnson wrote:
>>>> I’ve seen quite a few of these OBDII-plugin devices in recent years. Not just HUDs, but insurance company driving behaviour monitors, dongles, etc. While most modern cars provide at least some standard OBDII PID support (such as speed, fuel level, etc), Tesla have been notable in their absence of any such support.
>>>> 
>>>> Navdy, Exploride, Hudly, Garmin HUD, iScout; none work with Tesla cars.
>>>> 
>>>> Software wise it is quite simple to do. The only issue I see is dedicating one CAN bus port to this (but we’ve got three). On some cars, it might be possible to multiplex this on top of an existing CAN bus (so long as there is no conflict on the CAN IDs used or bus speed).
>>>> 
>>>> Regards, Mark.
>>>> 
>>>>> On 2 May 2017, at 7:37 AM, Greg D. <gregd2350 at gmail.com> wrote:
>>>>> 
>>>>> Hi Mark,
>>>>> 
>>>>> I'm really interested in the down-stream OBDII connection (ECU
>>>>> emulator).  I would like to use it to drive a Wi-Fi Hotspot dongle
>>>>> (T-Mobile's "SyncUp Drive").  Thanks for including this.
>>>>> 
>>>>> Besides providing a hotspot for the car's passengers, and the intended
>>>>> vehicle telematics, it could also give the OVMS module a Wi-Fi
>>>>> alternative to the 3G modem, at least when the car is awake.  I presume
>>>>> the modem would be the preferred connection for lower power states.
>>>>> 
>>>>> Greg
>>>>> 
>>>>> 
>>>>> Mark Webb-Johnson wrote:
>>>>>> Along with some HUDs, I’ve been experimenting with a little OBDII
>>>>>> display that costs around US$25 (quantity: 1). Connection is via OBDII
>>>>>> (CAN bus) - the idea being that we will emulate an OBDII ECU on one of
>>>>>> our CAN buses that connects to this. So, we can output battery
>>>>>> temperate where the unit expects coolant temperature, SOC% as fuel
>>>>>> level, etc. MCU in that unit is a GD32F103 (like an STM32, but
>>>>>> 108MHz). Input is via a little jog-left, jog-right, push-to-click
>>>>>> button on the front. Just an idea and something I’m messing around with.
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