[Ovmsdev] indirect TPMS in app

Mon Jan 18 01:51:16 HKT 2021

Everyone,

this is now fully implemented and committed.

Please note I did a slight change regarding the wheel layout and "Y" 
message structure, to better support custom layouts.

  * The TPMS wheel layout now is defined by
    OvmsVehicle::GetTpmsLayout(), which can be overridden by a vehicle
    to implement custom layouts. The default is the proposed FL,FR,RL,RR.
  * The wheel layout is included in the "Y" message as the first part,
    and the number of values is included for each vector.

See updated MP documentation here: 
https://docs.openvehicles.com/en/latest/protocol_v2/messages.html#car-tpms-message-0x59-y

Example messages from the DEMO vehicle:

Y4,FL,FR,RL,RR,4,206.8,216.5,275.8,175.8,0,4,33.0,33.0,34.0,38.0,0,4,95.0,93.0,96.0,74.0,0,4,0,0,0,1,0
W31.3982,33,25.4962,38,30,33,40,34,1

I'll take care of supporting "Y" in the Android App.

I've also added an automatic TPMS alert triggered by changes to the 
v.t.alert vector. Example alert text:

TPMS ALERT:
FR wheel ALERT: Health=91% Pressure=9.1kPa Temp=21C
RR wheel WARNING: Health=90% Pressure=9kPa Temp=9C

No alerts will be set automatically, you need to add setting some proper 
alert level if you'd like to use this new feature.

Regards,
Michael

Am 10.01.21 um 22:40 schrieb Michael Balzer:
> I read something about this being typical for all (or many?) VW 
> vehicles, apparently they don't have dedicated TPMS sensors but derive 
> the tyre "health" from the ESP sensors.
>
> If that's correct, there is no way we will ever be able to map the 
> values to actual temperatures & pressures.
>
> So… how about adding new relative TPMS metrics & warning/alert 
> indicators to be used alternatively to the current absolute 
> temperatures & pressures?
>
> We could add these now as vectors, and replace the previous single 
> metrics for temperatures & pressures by vectors as well. That would 
> reduce the metric payload size on both MQTT and the WebSocket 
> transport, and also adapt nicely to vehicles with more or less than 
> four wheels.
>
> Proposal: numbering scheme rows front to back, left to right per row. 
> For four wheels:
>
> v.t.pressure            fl,fr,rl,rr [kPa]
> v.t.temp             fl,fr,rl,rr    [°C]
> v.t.health         fl,fr,rl,rr    [%]
> v.t.alert              fl,fr,rl,rr    [0/1/2]
>
> The alert vector can use the same scheme as with the battery cells, 
> i.e. 0 = OK, 1 = warning, 2 = alert.
>
> The MP message "W" can be replaced by a new one. Proposal: Code "Y", data:
>
>   * number of wheels
>   * pressure values + staleness
>   * temp values + staleness
>   * health values + staleness
>   * alert values + staleness
>
> We can continue producing "W" messages for old clients in the field.
>
> Anything missing?
>
> If that's OK for all, I can make the necessary changes.
>
> Regards,
> Michael
>
>
> Am 09.01.21 um 19:35 schrieb sharkcow:
>> 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.
>>
>> sharkcow
>>
>>
>> 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?!)
>>>>
>>>> _______________________________________________
>>>> OvmsDev mailing list
>>>> OvmsDev at lists.openvehicles.com
>>>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>>>
>>>
>>> _______________________________________________
>>> OvmsDev mailing list
>>> OvmsDev at lists.openvehicles.com
>>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>>>
>> _______________________________________________
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>
> -- 
> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>
> _______________________________________________
> OvmsDev mailing list
> OvmsDev at lists.openvehicles.com
> http://lists.openvehicles.com/mailman/listinfo/ovmsdev

-- 
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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