[Ovmsdev] indirect TPMS in app

sharkcow sharkcow at gmx.de
Sun Jan 10 02:35:56 HKT 2021

Thanks for your input, Michael.

I agree that we could use the relative metrics to roughly estimate the
current assumed pressure from a reference value (which would have to be
updated every time a user presses the TPMS reset button...).

But: I'm afraid the correlation is not linear, probably not even
reproducible. Also, we have two pressure-related values per wheel, while
OVMS for now has a pressure and a temperature value.

So... I think I'd still prefer two relative indicators for the e-up in
the app. I can try to work on implementing a custom MP record.


Am 08.01.21 um 18:33 schrieb Michael Balzer:
> Sharkcow,
> as we don't have a new capabilities message scheme yet, conditional
> blocks are the way it works right now in the App.
> The meanings of standard metrics and message data fields should not be
> changed. Introducing custom metrics and a custom MP record is a possible
> solution.
> But having custom solutions for common things like this is a PITA. Maybe
> we can work something out to convert the readings into the standard
> metrics?
> For example: if you get a "health percentage", we could introduce a
> configuration for the "100%" health pressure level, so we can get an
> absolute value from that.
> Regards,
> Michael
> Am 08.01.21 um 15:12 schrieb sharkcow:
>> I have now figured out how to read and partly how to interpret the
>> metrics of the indirect TPMS on the e-up.
>> We get a "tyre emergency" and a "pressure diffusion" value for each
>> wheel.
>> Since the values are relative, I would like to transmit them to the app
>> as raw data and only display a percentage (100% means everything is ok).
>> Would it be ok to just introduce an if-statement in the app to detect
>> whether the vehicle type is an e-up and change the default displays
>> accordingly?
>> sharkcow
>> PS: I feel this value (incl. a useful alert value) would be very
>> beneficial: I just found out that I had lost quite some pressure over
>> the 2 years I own the vehicle without TPMS reacting. The metrics on OBD
>> showed a nicely measureable change however, which could easily be used
>> to have OVMS notify me. (Yes, I should have checked the pressure
>> regularly, but hey: what's a TPMS for?!)
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