From 2e72a03b9368bac8635e760fb0d62dd7ff388f0f Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 19 Mar 2020 22:56:14 +0100
Subject: [PATCH] steinhart_hart: fix equation

---
 src/command_parser.rs |  4 ++--
 src/main.rs           |  5 ++---
 src/steinhart_hart.rs | 22 ++++++----------------
 3 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/src/command_parser.rs b/src/command_parser.rs
index 3f3adae..b82e54f 100644
--- a/src/command_parser.rs
+++ b/src/command_parser.rs
@@ -110,7 +110,7 @@ pub enum PidParameter {
 #[derive(Debug, Clone, PartialEq)]
 pub enum ShParameter {
     T0,
-    R,
+    B,
     R0,
 }
 
@@ -353,7 +353,7 @@ fn steinhart_hart_parameter(input: &[u8]) -> IResult<&[u8], Result<Command, Erro
     let (input, _) = whitespace(input)?;
     let (input, parameter) =
         alt((value(ShParameter::T0, tag("t0")),
-             value(ShParameter::R, tag("r")),
+             value(ShParameter::B, tag("b")),
              value(ShParameter::R0, tag("r0"))
         ))(input)?;
     let (input, _) = whitespace(input)?;
diff --git a/src/main.rs b/src/main.rs
index 9a4b39d..7b19187 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -243,7 +243,7 @@ fn main() -> ! {
                                             channel,
                                         );
                                         let _ = writeln!(socket, "- t0={}", state.sh.t0);
-                                        let _ = writeln!(socket, "- r={}", state.sh.r);
+                                        let _ = writeln!(socket, "- b={}", state.sh.b);
                                         let _ = writeln!(socket, "- r0={}", state.sh.r0);
                                         let _ = writeln!(socket, "");
                                     }
@@ -355,10 +355,9 @@ fn main() -> ! {
                                     use command_parser::ShParameter::*;
                                     match parameter {
                                         T0 => sh.t0 = value,
-                                        R => sh.r = value,
+                                        B => sh.b = value,
                                         R0 => sh.r0 = value,
                                     }
-                                    sh.update();
                                     let _ = writeln!(socket, "Steinhart-Hart equation parameter updated");
                                 }
                                 Command::PostFilter { channel, rate } => {
diff --git a/src/steinhart_hart.rs b/src/steinhart_hart.rs
index fd3b099..de4d643 100644
--- a/src/steinhart_hart.rs
+++ b/src/steinhart_hart.rs
@@ -4,38 +4,28 @@ use num_traits::float::Float;
 #[derive(Clone, Debug)]
 pub struct Parameters {
     pub t0: f64,
-    pub r: f64,
+    pub b: f64,
     pub r0: f64,
-
-    r_fact: f64,
 }
 
 impl Parameters {
-    /// Update the cached r_fact
-    pub fn update(&mut self) {
-        self.r_fact = (self.r / self.r0).ln();
-    }
-
     /// Perform the voltage to temperature conversion.
     ///
     /// Result unit: Kelvin
     ///
     /// TODO: verify
-    pub fn get_temperature(&self, b: f64) -> f64 {
-        let inv_temp = 1.0 / self.t0 + self.r_fact / b;
+    pub fn get_temperature(&self, r: f64) -> f64 {
+        let inv_temp = 1.0 / self.t0 + (r / self.r0).ln() / self.b;
         1.0 / inv_temp
     }
 }
 
 impl Default for Parameters {
     fn default() -> Self {
-        let mut p = Parameters {
+        Parameters {
             t0: 0.001_4,
-            r: 0.000_000_099,
+            b: 0.000_000_099,
             r0: 5_110.0,
-            r_fact: 0.0,
-        };
-        p.update();
-        p
+        }
     }
 }