- Modified some thermocouple functions to use f64 instead of f32

- Added thermistor
- Added resistive divider

Cargo.toml

@@ -9,7 +9,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.3.3"
+version = "0.3.4"
 edition = "2021"
 repository = "https://git.bfpower.io/BFPOWER/physical"
 readme = "README.md"
@@ -107,7 +107,9 @@ readme.workspace = true
 license.workspace = true
 
 [features]
-thermocouple_k = []
+resistive-divider = []
+thermocouple-k = ["libm"]
+thermistor = ["libm"]
 lm35 = []
 pid = []
 stm32 = []
@@ -115,7 +117,7 @@ stm32 = []
 [dependencies]
 uom = { workspace = true }
 num-traits = { workspace = true }
-libm = { workspace = true }
+libm = { workspace = true, optional = true }
 serde = { workspace = true, optional = true }
 
 #---------------------------------------------------------------------------------------------------------------------

src/lib.rs

@@ -5,5 +5,7 @@ pub mod control;
 pub mod error;
 
 pub mod adc;
+#[cfg(feature = "resistive-divider")]
+pub mod resistive_divider;
 
 pub use error::CriticalError;

src/resistive_divider.rs

@@ -0,0 +1,31 @@
+use uom::si::electric_potential::volt;
+use uom::si::electrical_resistance::ohm;
+use uom::si::quantities::{ElectricPotential, ElectricalResistance};
+
+/// 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: ElectricPotential<f32>,
+    voltage_read: ElectricPotential<f32>,
+    r2: ElectricalResistance<f32>,
+) -> ElectricalResistance<f32> {
+    let volts_src = voltage_src.get::<volt>();
+    let volts_read = voltage_read.get::<volt>();
+    let ohms2 = r2.get::<ohm>();
+    
+    let ohms1 = ohms2 * (volts_src / volts_read - 1.0);
+    ElectricalResistance::new::<ohm>(ohms1)
+}
+
+/// 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: ElectricPotential<f32>,
+    voltage_read: ElectricPotential<f32>,
+    r1: ElectricalResistance<f32>,
+) -> ElectricalResistance<f32> {
+    let volts_src = voltage_src.get::<volt>();
+    let volts_read = voltage_read.get::<volt>();
+    let ohms1 = r1.get::<ohm>();
+    
+    let ohms2 = ohms1 * (1.0  / (volts_src / volts_read) - 1.0);
+    ElectricalResistance::new::<ohm>(ohms2)
+}

src/transducer/part/mod.rs

@@ -3,5 +3,8 @@ mod thermocouple;
 #[cfg(feature = "lm35")]
 pub mod lm35;
 
-#[cfg(feature = "thermocouple_k")]
+#[cfg(feature = "thermistor")]
+pub mod thermistor;
+
+#[cfg(feature = "thermocouple-k")]
 pub use thermocouple::type_k as thermocouple_k;

src/transducer/part/thermistor.rs

@@ -0,0 +1,33 @@
+use libm::{log, logf};
+use uom::si::electrical_resistance::ohm;
+use uom::si::quantities::{ThermodynamicTemperature, ElectricalResistance};
+use uom::si::thermodynamic_temperature::kelvin;
+
+/// Convert thermistor resistance to a temperature using beta parameter equation
+pub fn convert_beta(
+    resistance: ElectricalResistance<f32>,
+    beta: f32,
+    reference_temp: ThermodynamicTemperature<f32>,
+    reference_resist: ElectricalResistance<f32>,
+) -> ThermodynamicTemperature<f32> {
+    let ohms = resistance.get::<ohm>();
+    let reference_kelvin = reference_temp.get::<kelvin>();
+    let reference_ohms = reference_resist.get::<ohm>();
+
+    let result_kelvin = 1.0 / ((1.0 / reference_kelvin) + (1.0 / beta) * logf(ohms / reference_ohms));
+    ThermodynamicTemperature::new::<kelvin>(result_kelvin)
+}
+
+/// Convert thermistor resistance to a temperature using Steinhart-Hart equation
+pub fn convert_steinhart(
+    resistance: ElectricalResistance<f32>,
+    a: f64,
+    b: f64,
+    c: f64,
+) -> ThermodynamicTemperature<f32> {
+    let ohms = resistance.get::<ohm>() as f64;
+    
+    let log_omhs = log(ohms);
+    let kelvins = 1.0 / (a + b * log_omhs + c * log_omhs * log_omhs * log_omhs);
+    ThermodynamicTemperature::new::<kelvin>(kelvins as f32)
+}

src/transducer/part/thermocouple/mod.rs

@@ -1,2 +1,2 @@
-#[cfg(feature = "thermocouple_k")]
+#[cfg(feature = "thermocouple-k")]
 pub mod type_k;

src/transducer/part/thermocouple/type_k.rs

@@ -1,5 +1,7 @@
+//! Note - Thermocouple conversion uses [f64] arithmetic internally.
+
+use libm::pow;
 use crate::error::InvalidValue;
-use libm::powf;
 use uom::si::electric_potential::millivolt;
 use uom::si::quantities::{ElectricPotential, ThermodynamicTemperature};
 use uom::si::thermodynamic_temperature::degree_celsius;
@@ -7,7 +9,7 @@ use uom::si::thermodynamic_temperature::degree_celsius;
 fn _convert(
     voltage: ElectricPotential<f32>,
 ) -> Result<ThermodynamicTemperature<f32>, InvalidValue> {
-    let mv = voltage.get::<millivolt>();
+    let mv = voltage.get::<millivolt>() as f64;
     let mv_pow2 = mv * mv;
     let mv_pow3 = mv_pow2 * mv;
     let mv_pow4 = mv_pow3 * mv;
@@ -27,7 +29,7 @@ fn _convert(
             + -1.0450598E-2 * mv_pow7
             + -5.1920577E-4 * mv_pow8;
 
-        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius))
+        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius as f32))
     } else if mv > 0.0 && mv < 20.644 {
         let mv_pow7 = mv_pow6 * mv;
         let mv_pow8 = mv_pow7 * mv;
@@ -43,7 +45,7 @@ fn _convert(
             + 1.057734E-6 * mv_pow8
             + -1.052755E-8 * mv_pow9;
 
-        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius))
+        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius as f32))
     } else if mv >= 20.644 && mv <= 54.886 {
         let celsius = 1.318058e2
             + 4.830222E+1 * mv
@@ -53,7 +55,7 @@ fn _convert(
             + 8.802193E-6 * mv_pow5
             + -3.110810E-8 * mv_pow6;
 
-        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius))
+        Ok(ThermodynamicTemperature::new::<degree_celsius>(celsius as f32))
     } else {
         Err(InvalidValue)
     }
@@ -107,11 +109,10 @@ pub fn convert_polynomial(
     _convert(voltage + voltage_correction)
 }
 
-//TODO: This is not working, check libm pow.
 pub fn temp_to_voltage_poly(
     temperature: ThermodynamicTemperature<f32>,
 ) -> Result<ElectricPotential<f32>, InvalidValue> {
-    let celsius = temperature.get::<degree_celsius>();
+    let celsius = temperature.get::<degree_celsius>() as f64;
     let cel_pow2 = celsius * celsius;
     let cel_pow3 = cel_pow2 * celsius;
     let cel_pow4 = cel_pow3 * celsius;
@@ -135,11 +136,11 @@ pub fn temp_to_voltage_poly(
             + -0.198892668780E-19 * cel_pow9
             + -0.163226974860E-22 * cel_pow10;
 
-        Ok(ElectricPotential::new::<millivolt>(mv))
+        Ok(ElectricPotential::new::<millivolt>(mv as f32))
     } else if celsius >= 0.0 && celsius <= 1372.0 {
         let base = celsius - 0.126968600000E+03;
         let exp = -0.118343200000E-03 * (base * base);
-        let addition = powf(0.1185976, exp);
+        let addition = pow(0.1185976, exp);
 
         let mv = -0.176004136860E-01
             + 0.389212049750E-01 * celsius
@@ -153,7 +154,7 @@ pub fn temp_to_voltage_poly(
             + -0.121047212750E-25 * cel_pow9
             + addition;
 
-        Ok(ElectricPotential::new::<millivolt>(mv))
+        Ok(ElectricPotential::new::<millivolt>(mv as f32))
     } else {
         Err(InvalidValue)
     }