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mysensors / MySensors

MySensors library and examples
https://www.mysensors.org
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V_Unit_Prefix for S_weight? #1284

Open flatsiedatsie opened 5 years ago

flatsiedatsie commented 5 years ago

Shouldn't users be able to set what weight scale they are measuring in?

For example: Kilograms, grams, or even non-metric things?

Or is that perhaps what that 'V_Impedance' is for?

mfalkvidd commented 5 years ago

For S_TEMP / V_TEMP, the unit is decided by the controller's isMetric setting. Reference https://github.com/mysensors/MySensors/blob/a1282f358aadfe3dcd5b486778274a8ddc869ac5/core/MySensorsCore.h#L89

Would it make sense to use something similar for S_WEIGHT? Or should units be handled in some other way? The current implementation for temp does't support Kelvin for example, so maybe the current implementation is i sufficient?

mfalkvidd commented 5 years ago

Are there any specifications we could adapt, instead of inventing our own? OMA LightweightM2M has this specification for a "load" sensor. They use a free-form string for specifying the unit. That approach is flexible, but maybe too flexible? Could we find other useful specifications?

mfalkvidd commented 5 years ago

And no, impedance is not related. This is what impedance is used for:

In addition to measuring weight, the bathroom scale calculates body composition by sending a mild electrical impulse through the body. The measured electrical resistance is used – together with information on age, gender and height – to calculate body fat, body water, and more.

flatsiedatsie commented 5 years ago

Ah, so that's what its for! Interesting.

I thought it would be useful to just add V_UNIT_PREFIX? That way the device can specify in what scale it's measuring (grams/kilograms).

mfalkvidd commented 5 years ago

Sorry, I thought you proposed a new type, but I just noticed that V_UNIT_PREFIX is already used for distance, air quality and dust level.

Yes, using V_UNIT_PREFIX for any value that can have different units would be quite useful. In addition to the existing uses and weight (as per your suggestion) I think it would make sense to also use V_UNIT_PREFIX for things like voltage, current, atmospheric pressure, power usage (although V_KWH unfortunately already implies a unit), flow and volume.

flatsiedatsie commented 5 years ago

Exactly!

See also this issue for some musing on making some universal V_TYPES to help presentation in the UX

mfalkvidd commented 5 years ago

See also https://github.com/mysensors/MySensors/issues/1312 for yet another discussion on the same topic.

flatsiedatsie commented 5 years ago

Yes I thought I'd create an official proposal for it.