Feature: auto-detect SoC precision for MQTT Battery provider

[AndreasBoehm]

With this change we will allow users to set the decimal places (or precision) of the SoC when the MQTT Battery Provider is used.

Live View

Console

18:56:32.934 > MqttBattery: Updated SoC to 49.93 from 'solarLights/battery/stateOfCharge'
18:56:33.076 > MqttBattery: Updated voltage to 52.68 from 'solarLights/battery/voltage'
...
18:56:51.454 > [DPL] battery interface enabled, SoC 49.9 % (used), age 3 s (valid)
18:56:51.462 > [DPL] BMS: 52.68 V, MPPT: -1.00 V, inverter 1164a00aaa1f: 52.80 
18:56:51.471 > [DPL] battery voltage 52.68 V, load-corrected voltage 52.68 V @ 0 W, factor 0.00130 1/A

[schlimmchen]

Hm... I can see why we need something like this. Should it be a user setting? I think it should not be. Can't we do something like this:

// MqttBattery class member
uint8_t _socPrecision = 0;

onMqttMessageSoC(...) {
    ...
    unsigned factor = 10;
    uint8_t precision = 0;
    while (precision < 2) {
        if (std::floor(*soc * factor) == std::floor(*soc) * factor) { break; }
        ++precision;
        factor *= 10;
    }
    _socPrecision = std::max(_socPrecision, precision);
}

This way the precision would be learned automatically. What do you think?

[AndreasBoehm]

Very good idea @schlimmchen. Thanks for providing code, it works perfectly. I adjusted my PR accordingly.

[schlimmchen]

Did you forget to include the change to MqttBattery.h?

[AndreasBoehm]

Did you forget to include the change to MqttBattery.h?

Yes i did 🙈
Changes pushed.