Telemetry: add constants to calculated telemetry and enable negative Ratio

[blopa1961]

This request replaced by #4785 please close it.

[frankiearzu]

@blopa1961 ratio can be use to decrease the value. Any value lower than 25.5 (or 255 on some GUI with no decimal) decreases the value. 25.5 = 100%, if you want / 10 (or 10%), use ratio 2.5 (25 on GUI with no decimal). In 2.11 we have an enhancement to the GUI to make ratio easier to understand. #4648

Question: What protocol do you use to connect to your Matek?? What sensor ID?? That 1800 instead of 180.0 seems that the precision of 1 (1 decimal point) is not setup in the processing of the protocol telemetry. Internally, all telemetry comes as integers, and depending of the internal def of the sensor, it will know if it is Prec1 (1 decimal). So a raw integer 1800 becomes 180.0 in the GUI. This is not affected by the Precision on the sensor setup GUI (that will auto-adjust the value as needed), the internal definition needs to be right/correct to start.

[blopa1961]

I tested iNav with the G474 and the horizon is wrong (barely moves) with the precision to 1 decimal, it actually expects -1800 to 1800 and -900 to 900.

This means I will need to use a 255 ratio with my SR8...

[frankiearzu]

Ratio=0 (or --) means skip the scaling logic, so is the same as 100%. I agree about knowing what ratio is 100% (25.5) that's why we are adding the percent number to the GUI. Originally Ratio was only for voltages, but now I see a lot more different uses.