thermostat: Add channel_state mod for PID Control

src/thermostat/channel_state.rs

@@ -0,0 +1,97 @@
+use smoltcp::time::{Duration, Instant};
+use uom::si::{
+    f64::{
+        ElectricPotential,
+        ElectricalResistance,
+        ThermodynamicTemperature,
+        Time,
+    },
+    electric_potential::volt,
+    electrical_resistance::ohm,
+    thermodynamic_temperature::degree_celsius,
+    time::millisecond,
+};
+use crate::thermostat::{
+    ad7172,
+    steinhart_hart as sh,
+};
+use crate::pid::pid;
+
+const R_INNER: f64 = 2.0 * 5100.0;
+const VREF_SENS: f64 = 3.3 / 2.0;
+
+pub struct ChannelState {
+    pub adc_data: Option<u32>,
+    pub adc_calibration: ad7172::ChannelCalibration,
+    pub adc_time: Instant,
+    pub adc_interval: Duration,
+    /// i_set 0A center point
+    pub center: ElectricPotential,
+    pub dac_value: ElectricPotential,
+    pub pid_engaged: bool,
+    pub pid: pid::Controller,
+    pub sh: sh::Parameters,
+}
+
+impl ChannelState {
+    pub fn new(adc_calibration: ad7172::ChannelCalibration) -> Self {
+        ChannelState {
+            adc_data: None,
+            adc_calibration,
+            adc_time: Instant::from_secs(0),
+            // default: 10 Hz
+            adc_interval: Duration::from_millis(100),
+            center: ElectricPotential::new::<volt>(1.5), 
+            dac_value: ElectricPotential::new::<volt>(0.0),
+            pid_engaged: false,
+            pid: pid::Controller::new(pid::Parameters::default()),
+            sh: sh::Parameters::default(),
+        }
+    }
+
+    pub fn update(&mut self, now: Instant, adc_data: u32) {
+        self.adc_data = if adc_data == ad7172::MAX_VALUE {
+            // this means there is no thermistor plugged into the ADC.
+            None
+        } else {
+            Some(adc_data)
+        };
+        self.adc_interval = now - self.adc_time;
+        self.adc_time = now;
+    }
+
+    /// Update PID state on ADC input, calculate new DAC output
+    pub fn update_pid(&mut self) -> Option<f64> {
+        let temperature = self.get_temperature()?
+            .get::<degree_celsius>();
+        let pid_output = self.pid.update(temperature);
+        Some(pid_output)
+    }
+
+    pub fn get_adc_time(&self) -> Time {
+        Time::new::<millisecond>(self.adc_time.total_millis() as f64)
+    }
+
+    pub fn get_adc_interval(&self) -> Time {
+        Time::new::<millisecond>(self.adc_interval.total_millis() as f64)
+    }
+
+    pub fn get_adc(&self) -> Option<ElectricPotential> {
+        Some(self.adc_calibration.convert_data(self.adc_data?))
+    }
+
+    /// Get `SENS[01]` input resistance
+    pub fn get_sens(&self) -> Option<ElectricalResistance> {
+        let r_inner = ElectricalResistance::new::<ohm>(R_INNER);
+        let vref = ElectricPotential::new::<volt>(VREF_SENS);
+        let adc_input = self.get_adc()?;
+        let r = r_inner * adc_input / (vref - adc_input);
+        Some(r)
+    }
+
+    pub fn get_temperature(&self) -> Option<ThermodynamicTemperature> {
+        let r = self.get_sens()?;
+        let temperature = self.sh.get_temperature(r);
+        Some(temperature)
+    }
+}

src/thermostat/mod.rs

@@ -3,3 +3,4 @@ pub mod max1968;
 pub mod thermostat;
 pub mod ad7172;
 pub mod steinhart_hart;
+pub mod channel_state;