[Ovmsdev] HUD Demo

Greg D. gregd2350 at gmail.com
Sat Jan 13 15:38:39 HKT 2018

Hi Mark,

Yes, it seems to track pretty well, though if I punch it, the Roadster
can easily out run the display.  :)

A couple of things I noticed after shooting the video.  First, it seems
that the conversion from RPM to MPH is running slightly high.  The car
was telling me I was in the low 50's, and the HUD was up around 57.  I
need to get some controlled runs in to see just how far off it is, so we
can adjust the conversion rate.  Fortunately this is Roadster-specific,
and in the TR vehicle code, so other vehicles aren't affected.

Second, I'm still wrestling with what the default metric should be for
feeding the fuel flow rate display (PID 0x10).  This is the upper right
corner display on my HUD, and seems to be a pretty common metric among
OBDII devices and software.  The display value runs from 0-19.9, and the
conversion is not very precise (we lose a lot of bits in all the back
and forth conversions), so there aren't many things that fit in that
space.  The CAN Bus 12v supply voltage is about the best I can do.  Does
anyone have a better metric? 

Separate from the HUD, when running the V2 Android app I see that the
rear tire pressure isn't correct (it reads 2.3 PSI, for tires that the
car is reading at 34 PSI), and the rear temperatures are both zero. 
Looking at the metrics on the Raspberry Pi console, I see that the rear
temps aren't even populated (vs populated with zeros), and the pressure
definitely is way off.  So, it's not the V2 server; something is odd
with the reading of the actual data from the car. 

The TPMS system on the 2.x Roadsters is a well known "piece of work", so
at first I wasn't too surprised.  But since the car itself shows proper
values for all 4 tires, I think the issue is on the OVMS module side. 
I've seen it a couple of times; same issue, same tires, and never seen
it correct.  I presume it was working correctly on the prior products
(v1 / v2), but have no experience with them myself.  Is this just
something where I just didn't give the module sufficient time to gather
its data? 

I'm not sure I'm ready to write an ELM emulator...  Let's see what sort
of demand and usage there is for this interface.  The OBDWiz software is
in that same family as Torque, so I was already thinking of including a
short clip of it running with the car too.  Also I should show an
example of customizing the metric map.  Next video... 


Mark Webb-Johnson wrote:
> Very cool. Seems to update well.
> I was thinking about those little Bluetooth OBDII transmitters and the Torque Pro software that allows you to build custom dashboard displays on your phone. Could be pretty useful. Of course the OVMS v3 could also emulate the Bluetooth/WiFi ELM327 protocol directly to produce the same data but without the cable.
> Regards, Mark
>> On 13 Jan 2018, at 8:41 AM, Greg D. <gregd2350 at gmail.com> wrote:
>> Hi folks,
>> Our first sunny day here in quite a while, so I thought it would be a
>> good time to take a quick video of the obd2ecu task (OBDII ECU
>> translator) driving a HUD display.  This is a rough draft - I'll make a
>> more polished video when my kids visit in a few weeks and can help with
>> the camera work.
>> https://www.youtube.com/watch?v=AEyjckZBgOs
>> Enjoy!
>> Greg
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