[Ovmsdev] Celcius vs Fahrenheit, Kilometers vs Miles

[Mark Webb-Johnson]

In the car module, and protocol, there is a setting for Miles vs Kilometers and all the distance based measurements (speed, ideal and estimated ranges) are sent from the module in those units.

The protocol states that temperatures (pem, motor, battery, ambient and tpms) should be sent in celcius, and tpms pressures in PSI - and that is what is currently done.

We don't currently convert these to user-suitable units in the iOS App. We leave them in celcius and psi.

Doing the conversion in the App is certainly possible, but my question is how to control this and what to do?

Options I see:

Use the Miles/Kilometer value coming from the car.
Use the iOS NSLocale system to read user preferences from the device itself, and convert _everything_ to that.
Use the iOS NSLocale system to read user preferences from the device itself, and convert just temperatures/pressures to that.

I've left out [4] "have individual settings in the app for each of temperatures, distance and pressure" as it is overly complicated.

We could convert temperatures from celcius to fahrenheit (using Tf = (9/5)*Tc+32).
We could convert pressures from PSI to kPa (using Pkpa = Ppsi * 6.895).

For tire pressures, what is currently used in Europe? I still see PSI used here in Hong Kong, even thought we use Kilometers for distance, but do we need to convert this to something else? I notice the roadster still shows pressures in PSI even though the car is metric and shows kilometers. Is it OK to leave this in PSI?

What do US cars show for ambient and tpms temperatures on the in-car VDS? Celcius / Fahrenheit?

Regards, Mark.

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