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Hi folks,<br>
<br>
To those who care about such things, I have a dilemma to solve and
can use some guidance: How to keep the various OBDII peripherals
(HUDs, Dongles, etc) awake when the car is on but is not moving.<br>
<br>
I have a small sample of devices (three to be exact) to use for
developing the OBDII ECU Simulator (translator). The devices that
are intended for installation in a car use various methods to
determine when to shut down to conserve power, since the OBDII 12v
power from the battery does not turn off with the car. They are
clearly not designed to work with EVs.<br>
<br>
- HUD: If not moving (speed = 0) for more than a second or two,
turn off if below some minimum engine RPM.<br>
- SyncUp Drive dongle: Turn off if no variation in Engine RPM,
regardless of value, for more than 10 minutes<br>
<br>
Since an EV's motor has a direct gearing to the wheels, a straight
feed-through of RPM to the device causes them to shut down when the
car stops. Since they stop polling the ECU when off, the devices do
not start back up when the car starts moving. They require a power
cycle to resume. The current OVMS ECU code is sufficient to keep
the SyncUp dongle from shutting down, as I simulate a very small
(0-15 RPM) motor "jitter" to make the dongle think that there is
something mechanical connected. But it's not sufficient to keep my
HUD alive; it takes about 500 RPM to keep it from shutting down if
the car isn't moving.<br>
<br>
<b>My questions:</b><br>
<br>
1. For those who want to attach a HUD-type display to the OVMSv3
product, is a "500 RPM when at zero speed" algorithm acceptable?
I'm guessing that motor RPM isn't important if not moving. If you
want to map Engine RPM to some other source, be aware that might be
affected by this behavior. (Note: the mapping of these 4 PIDs is
static right now.) My own use of the SyncUp Drive dongle is for the
Wi-Fi hotspot it provides, so I don't care about what it reports.<br>
<br>
2. The Diagnostic dongles (OBDwiz in my case) seem to stay
connected as long as there are responses to its polling, regardless
of value. Mine is USB powered, however; I don't know how the
Bluetooth-based devices behave. If anyone has one, I'd like to know
what it does.<br>
<br>
3. Are there any HUD / Dongle PIDs that you are especially
interested in seeing displayed / tracked?<br>
<br>
As for the real power cycling of the external device, the current
plan is to match the enabling of the external 12v feed-through with
the state of Vehicle On. That will drop the external device power
when the car turns off, and turn it on when the car is "started".
You can also control it manually from the command line.<br>
<br>
If you want to try the OBDII ECU simulator, it currently supports
vehicle speed, engine RPM (derived from speed, assuming a Roadster's
gearing), coolant temperature (reported from motor temp), and fuel
flow (reported from Battery SoC, but the math is currently wrong).
There are ten other PIDs respond with simulated values (e.g. engine
load, air intake temp, etc.).<br>
<br>
OVMS > <b>obdii ecu start can3<br>
</b>OBDII ECU has been started<br>
OVMS > <b>power ext12v on</b><br>
Power mode of ext12v is now on<br>
I (14194) ext12v: Powering on external 12V devices<br>
<br>
Attach your HUD/Dongle to CAN3 on the Accessory port. <br>
<br class="">
<tt> DB26 OBDII Female Signal name</tt><tt><br class="">
</tt><tt> ------- ------- --------------------------</tt><tt><br
class="">
</tt><tt> 6 14 CAN3-L</tt><tt><br class="">
</tt><tt> 16 6 CAN3-H</tt><tt><br class="">
</tt><tt> (also 120 ohm resistor between 14
& 6 for</tt><tt> </tt><tt>termination)</tt><tt><br class="">
</tt><tt> 8 4 & 5 Chassis & Signal Grounds</tt><tt><br
class="">
</tt><tt> 18 16 +12v switched output</tt><tt><br
class="">
</tt><tt> </tt><br>
Also, there is a command "obdii ecu privacy [on|off]" to disable /
enable the reporting of your vehicle VIN, should you want to keep
the dongle from seeing it. Default is privacy on (not reported).
The SyncUp folks appear to have a relationship with the car
insurance industry, and the implications of that could be
"significant."<br>
<br>
Enjoy,<br>
<br>
Greg<br>
<br>
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