Initial proof of concept

src/circuit/mod.rs

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+#[cfg(feature = "resistive-divider")]
+pub mod resistive_divider;

src/circuit/resistive_divider.rs

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+use crate::quantity::{Ohms, Volts};
+
+/// Given the resistance of the second resistor in a resistive voltage divider, calculate the resistance of the first resistor.
+pub fn solve_r1(
+    voltage_src: Volts<f32>,
+    voltage_read: Volts<f32>,
+    r2: Ohms<f32>,
+) -> Ohms<f32> {
+    Ohms(r2.0 * (voltage_src.0 / voltage_read.0 - 1.0))
+}
+
+/// Given the resistance of the first resistor in a resistive voltage divider, calculate the resistance of the second resistor.
+pub fn solve_r2(
+    voltage_src: Volts<f32>,
+    voltage_read: Volts<f32>,
+    r1: Ohms<f32>,
+) -> Ohms<f32> {
+    Ohms((r1.0 * voltage_read.0) / (voltage_src.0 - voltage_read.0))
+}
+
+// ---------------------------------------------------------------------------------------------------------------------
+// ----- Tests ------------------------
+// ---------------------------------------------------------------------------------------------------------------------
+#[cfg(test)]
+mod tests {
+    use crate::quantity::{OhmsVal, VoltsVal};
+    use super::*;
+    use float_cmp::assert_approx_eq;
+
+    #[test]
+    fn solve_r1_test() {
+        let resistance = solve_r1(3.3.volts(), 2.0.volts(), 1_000.0.ohms());
+
+        assert_approx_eq!(f32, 650.0, resistance.0);
+    }
+
+    #[test]
+    fn solve_r2_test() {
+        let resistance = solve_r2(3.3.volts(), 2.0.volts(), 1_000.0.ohms());
+
+        assert_approx_eq!(f32, 1538.462, resistance.0);
+    }
+}