steinhart_hart: Beta Parameter uom dimensions

The Beta Parameter is not dimensionless, and has unit Kelvin.
Incorporate that into the type system for better checks.

README.md

@@ -45,7 +45,7 @@ There are several options for flashing Thermostat. DFU requires only a micro-USB
 
 ### dfu-util on Linux
 * Install the DFU USB tool (dfu-util).
-* Convert firmware from ELF to BIN: `llvm-objcopy -O binary target/thumbv7em-none-eabihf/release/thermostat thermostat.bin` (you can skip this step if using the BIN from Hydra)
+* Convert firmware from ELF to BIN: `arm-none-eabi-objcopy -O binary thermostat thermostat.bin` (you can skip this step if using the BIN from Hydra)
 * Connect to the Micro USB connector to Thermostat below the RJ45.
 * Add jumper to Thermostat v2.0 across 2-pin jumper adjacent to JTAG connector.
 * Cycle board power to put it in DFU update mode

flake.lock

@@ -2,16 +2,16 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1722791413,
-        "narHash": "sha256-rCTrlCWvHzMCNcKxPE3Z/mMK2gDZ+BvvpEVyRM4tKmU=",
+        "lastModified": 1691421349,
+        "narHash": "sha256-RRJyX0CUrs4uW4gMhd/X4rcDG8PTgaaCQM5rXEJOx6g=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "8b5b6723aca5a51edf075936439d9cd3947b7b2c",
+        "rev": "011567f35433879aae5024fc6ec53f2a0568a6c4",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixos-24.05",
+        "ref": "nixos-23.05",
         "repo": "nixpkgs",
         "type": "github"
       }

flake.nix

@@ -1,7 +1,7 @@
 {
   description = "Firmware for the Sinara 8451 Thermostat";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+  inputs.nixpkgs.url = github:NixOS/nixpkgs/nixos-23.05;
   inputs.rust-overlay = { 
     url = "github:oxalica/rust-overlay";
     inputs.nixpkgs.follows = "nixpkgs";
@@ -47,7 +47,6 @@
         '';
 
         dontFixup = true;
-        auditable = false;
       };
     in {
       packages.x86_64-linux = {
@@ -62,8 +61,7 @@
       devShells.x86_64-linux.default = pkgs.mkShellNoCC {
         name = "thermostat-dev-shell";
         packages = with pkgs; [
-          rust llvm
-          openocd dfu-util
+          rust openocd dfu-util
           ] ++ (with python3Packages; [
             numpy matplotlib
           ]);

src/channels.rs

@@ -1,4 +1,4 @@
-use core::marker::PhantomData;
+use core::{cmp::max_by, marker::PhantomData};
 use heapless::{consts::U2, Vec};
 use num_traits::Zero;
 use serde::{Serialize, Serializer};
@@ -561,10 +561,9 @@ impl Channels {
     }
 
     pub fn current_abs_max_tec_i(&mut self) -> ElectricCurrent {
-        (0..CHANNELS)
-            .map(|channel| self.get_tec_i(channel).abs())
-            .max_by(|a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal))
-            .unwrap()
+        max_by(self.get_tec_i(0).abs(),
+               self.get_tec_i(1).abs(),
+               |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal))
     }
 }
 

src/command_handler.rs

@@ -34,13 +34,11 @@ use uom::{
             ElectricPotential,
             ElectricalResistance,
             ThermodynamicTemperature,
-            TemperatureInterval,
         },
         electric_current::ampere,
         electric_potential::volt,
         electrical_resistance::ohm,
-        thermodynamic_temperature::degree_celsius,
-        temperature_interval::kelvin,
+        thermodynamic_temperature::{degree_celsius, kelvin},
     },
 };
 
@@ -245,7 +243,7 @@ impl Handler {
         use super::command_parser::ShParameter::*;
         match parameter {
             T0 => sh.t0 = ThermodynamicTemperature::new::<degree_celsius>(value),
-            B => sh.b = TemperatureInterval::new::<kelvin>(value),
+            B => sh.b = ThermodynamicTemperature::new::<kelvin>(value),
             R0 => sh.r0 = ElectricalResistance::new::<ohm>(value),
         }
         send_line(socket, b"{}");
@@ -347,7 +345,7 @@ impl Handler {
 
     fn set_fan(socket: &mut TcpSocket, fan_pwm: u32, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
         if !fan_ctrl.fan_available() {
-            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have a fan!\" }");
+            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have fan!\" }");
             return Ok(Handler::Handled);
         }
         fan_ctrl.set_auto_mode(false);
@@ -376,7 +374,7 @@ impl Handler {
 
     fn fan_auto(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
         if !fan_ctrl.fan_available() {
-            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have a fan!\" }");
+            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have fan!\" }");
             return Ok(Handler::Handled);
         }
         fan_ctrl.set_auto_mode(true);

src/steinhart_hart.rs

@@ -3,12 +3,10 @@ use uom::si::{
     f64::{
         ElectricalResistance,
         ThermodynamicTemperature,
-        TemperatureInterval,
     },
     electrical_resistance::ohm,
     ratio::ratio,
     thermodynamic_temperature::{degree_celsius, kelvin},
-    temperature_interval::kelvin as kelvin_interval,
 };
 use serde::{Deserialize, Serialize};
 
@@ -20,18 +18,14 @@ pub struct Parameters {
     /// Resistance at base temperature
     pub r0: ElectricalResistance,
     /// Beta
-    pub b: TemperatureInterval,
+    pub b: ThermodynamicTemperature,
 }
 
 impl Parameters {
     /// Perform the resistance to temperature conversion.
     pub fn get_temperature(&self, r: ElectricalResistance) -> ThermodynamicTemperature {
-        let t0 = TemperatureInterval::new::<kelvin_interval>(self.t0.get::<kelvin>());
-
-        let inv_temp = 1.0 / t0 + (r / self.r0).get::<ratio>().ln() / self.b;
-        let temp = 1.0 / inv_temp;
-
-        ThermodynamicTemperature::new::<kelvin>(temp.get::<kelvin_interval>())
+        let inv_temp = 1.0 / self.t0.get::<kelvin>() + (r / self.r0).get::<ratio>().ln() / self.b.get::<kelvin>();
+        ThermodynamicTemperature::new::<kelvin>(1.0 / inv_temp)
     }
 }
 
@@ -40,7 +34,7 @@ impl Default for Parameters {
         Parameters {
             t0: ThermodynamicTemperature::new::<degree_celsius>(25.0),
             r0: ElectricalResistance::new::<ohm>(10_000.0),
-            b: TemperatureInterval::new::<kelvin_interval>(3800.0),
+            b: ThermodynamicTemperature::new::<kelvin>(3800.0),
         }
     }
 }