Save the current setpoint i_set directly

This avoids the need to back-calculate the current setpoint value back
from the DAC value when reporting, as it is a user-provided value.

README.md

@@ -184,7 +184,7 @@ postfilter rate can be tuned with the `postfilter` command.
 - Connect TEC module device 1 to TEC1- and TEC1+.
 - The GND pin is for shielding not for sinking TEC module currents.
 
-When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to heat up with a positive software current set point, and cool down with a negative current set point.
+When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to cool down with a positive software current set point, and heat up with a negative current set point.
 
 Testing heat flow direction with a low set current is recommended before installation of the TEC module.
 

src/channel_state.rs

@@ -1,11 +1,13 @@
 use smoltcp::time::{Duration, Instant};
 use uom::si::{
     f64::{
+        ElectricCurrent,
         ElectricPotential,
         ElectricalResistance,
         ThermodynamicTemperature,
         Time,
     },
+    electric_current::ampere,
     electric_potential::volt,
     electrical_resistance::ohm,
     thermodynamic_temperature::degree_celsius,
@@ -26,11 +28,10 @@ pub struct ChannelState {
     pub adc_calibration: ad7172::ChannelCalibration,
     pub adc_time: Instant,
     pub adc_interval: Duration,
-    /// VREF for the TEC (1.5V)
-    pub vref: ElectricPotential,
     /// i_set 0A center point
     pub center: CenterPoint,
     pub dac_value: ElectricPotential,
+    pub i_set: ElectricCurrent,
     pub pid_engaged: bool,
     pub pid: pid::Controller,
     pub sh: sh::Parameters,
@@ -44,10 +45,9 @@ impl ChannelState {
             adc_time: Instant::from_secs(0),
             // default: 10 Hz
             adc_interval: Duration::from_millis(100),
-            // updated later with Channels.read_vref()
-            vref: ElectricPotential::new::<volt>(1.5),
             center: CenterPoint::Vref,
             dac_value: ElectricPotential::new::<volt>(0.0),
+            i_set: ElectricCurrent::new::<ampere>(0.0),
             pid_engaged: false,
             pid: pid::Controller::new(pid::Parameters::default()),
             sh: sh::Parameters::default(),

src/channels.rs

@@ -58,7 +58,6 @@ impl Channels {
         let pwm = pins.pwm;
         let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm };
         for channel in 0..CHANNELS {
-            channels.channel_state(channel).vref = channels.read_vref(channel);
             channels.calibrate_dac_value(channel);
             channels.set_i(channel, ElectricCurrent::new::<ampere>(0.0));
         }
@@ -117,11 +116,7 @@ impl Channels {
     }
 
     pub fn get_i(&mut self, channel: usize) -> ElectricCurrent {
-        let center_point = self.get_center(channel);
-        let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
-        let voltage = self.get_dac(channel);
-        let i_tec = (voltage - center_point) / (10.0 * r_sense);
-        i_tec
+        self.channel_state(channel).i_set
     }
 
     /// i_set DAC
@@ -142,6 +137,7 @@ impl Channels {
         let voltage = i_tec * 10.0 * r_sense + center_point;
         let voltage = self.set_dac(channel, voltage);
         let i_tec = (voltage - center_point) / (10.0 * r_sense);
+        self.channel_state(channel).i_set = i_tec;
         i_tec
     }
 
@@ -429,7 +425,6 @@ impl Channels {
     }
 
     fn report(&mut self, channel: usize) -> Report {
-        let vref = self.channel_state(channel).vref;
         let i_set = self.get_i(channel);
         let i_tec = self.read_itec(channel);
         let tec_i = self.get_tec_i(channel);
@@ -446,7 +441,6 @@ impl Channels {
                 .map(|temperature| temperature.get::<degree_celsius>()),
             pid_engaged: state.pid_engaged,
             i_set,
-            vref,
             dac_value,
             dac_feedback: self.read_dac_feedback(channel),
             i_tec,
@@ -544,7 +538,6 @@ pub struct Report {
     temperature: Option<f64>,
     pid_engaged: bool,
     i_set: ElectricCurrent,
-    vref: ElectricPotential,
     dac_value: ElectricPotential,
     dac_feedback: ElectricPotential,
     i_tec: ElectricPotential,