Ethos Calculator

A compact scientific calculator for FrSky Ethos radios and the Ethos simulator. It runs as an Ethos System Tool, so it is available directly on the radio when you need quick field math, setup checks, or unit calculations.

Highlights

• Standard math with parentheses: +, -, *, /, and ^
• Scientific functions: sin, cos, tan, asin, acos, atan, sqrt, ln, and log
• Constants and saved values: pi, e, ans, and memory register m
• Percent and factorial postfix operators: % and !
• Degree/radian toggle with the D/R key
• Scientific notation entry with EE, such as 1e6
• Memory keys: MS, MR, M+, and MC
• Implicit multiplication for natural entries like 2pi, 2(3+4), and 2sin(30)
• Quick Tools mode from the radio PAGE key for throttle conversion, unit conversion, and Ohm's Law

Installation

Copy the calculator folder to the scripts folder on your radio SD card or simulator root:

scripts/calculator/main.lua
scripts/calculator/gfx/icon.png

Keep main.lua and the gfx folder together.

The tool will appear as "Calculator" in the system menu.

Basic Use

• Tap the on-screen keys to build an expression.
• Tap = or long-press ENTER to evaluate.
• Use DEL to remove the last character.
• Use AC to clear the current expression.
• Use D/R to switch trigonometry between degrees and radians.
• Use ANS to insert the previous result into the next expression.
• Press the radio PAGE key to switch between the calculator and Quick Tools.
• Press RTN to go back from a Quick Tools entry page to the Quick Tools menu, or from the Quick Tools menu back to the calculator.

The top line shows the current mode, PAGE hint, last answer, and memory value when memory is set.

Memory Keys

• MS stores the current value in memory.
• MR inserts the memory value into the expression.
• M+ adds the current value to memory.
• MC clears memory.

Memory can also be referenced in expressions with m or mem.

Quick Tools

Press PAGE to switch to Quick Tools, then tap a tool. Each tool opens an entry prompt with its own keypad. Enter the source value or values and tap OK or Solve. Tools stay on their entry page for repeated conversions until you tap Cancel or press RTN/PAGE. The result replaces the current calculator entry and is also stored as ans where practical.

Available Quick Tools:

Throttle Scale Converter

Converts between Spektrum-style 0-100% throttle values and Ethos-style +/-100% throttle values. Use the Swap button to flip the direction.

Examples:

0-100% to +/-100%: 75 -> +50
+/-100% to 0-100%: +50 -> 75

Unit Converter

Converts within a selected unit group. Tap the group selector to switch between channel, length, weight, and temperature. Tap either unit selector to cycle that side through the units in the selected group. Tapping Swap will swap the From and To units.

Unit Converter groups:

• Channel: PWM us, Channel %
• Length: mi, yd, ft, in, km, m, cm, mm
• Weight: kg, g, mg, lb, oz
• Temperature: degC, degF, Kelvin

Channel conversions reject source entries outside 800 to 2200 PWM us or outside -125 to +125 channel percent.

Ohm's Law Solver

Solves the remaining Ohm's Law values from any two entered values. Tap a parameter (Volts, Amps, Ohms, or Watts), enter its value, then tap another parameter and enter its value. Entered values appear in the status line below the main display as you enter them. Tap Solve to calculate the remaining two values.

Other

Graphics by Pixel Perfect https://www.flaticon.com/free-icon/keys_2891382