Treat VREF as always 1.5V when getting tec_i

Reading until the error falls into a certain tolerance might cause
bootlooping as the ADC values just might never settle. Average it out
instead.

README.md

@@ -106,7 +106,7 @@ formatted as line-delimited JSON.
 | `pwm <0/1> i_set <amp>`          | Disengage PID, set fixed output current                                       |
 | `pwm <0/1> pid`                  | Let output current to be controlled by the PID                                |
 | `center <0/1> <volt>`            | Set the MAX1968 0A-centerpoint to the specified fixed voltage                 |
-| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to measure from VREF                           |
+| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to a stable calibrated VREF                    |
 | `pid`                            | Show PID configuration                                                        |
 | `pid <0/1> target <deg_celsius>` | Set the PID controller target temperature                                     |
 | `pid <0/1> kp <value>`           | Set proportional gain                                                         |
@@ -264,6 +264,7 @@ with the following keys.
 | `temperature`  | Degrees Celsius | Steinhart-Hart conversion result derived from `sens` |
 | `pid_engaged`  | Boolean         | `true` if in closed-loop mode                        |
 | `i_set`        | Amperes         | TEC output current                                   |
+| `vref`         | Volts           | MAX1968 VREF (1.5 V)                                 |
 | `dac_value`    | Volts           | AD5680 output derived from `i_set`                   |
 | `dac_feedback` | Volts           | ADC measurement of the AD5680 output                 |
 | `i_tec`        | Volts           | MAX1968 TEC current monitor                          |
@@ -271,19 +272,18 @@ with the following keys.
 | `tec_u_meas`   | Volts           | Measurement of the voltage across the TEC            |
 | `pid_output`   | Amperes         | PID control output                                   |
 
-Note: With Thermostat v2 and below, the voltage and current readouts `i_tec` and `tec_i` are disabled and null due to faulty hardware that introduces a lot of noise in the signal.
-
 ## PID Tuning
 
 The thermostat implements a PID control loop for each of the TEC channels, more details on setting up the PID control loop can be found [here](./doc/PID%20tuning.md).
 
 ## Fan control
 
-Fan control commands are available for thermostat revisions with an integrated fan system:
+Fan control is available for the thermostat revisions with integrated fan system. For this purpose four commands are available:
 1. `fan` - show fan stats: `fan_pwm`, `abs_max_tec_i`, `auto_mode`, `k_a`, `k_b`, `k_c`.
-2. `fan auto` - enable auto speed controller mode, where fan speed is controlled by the fan curve `fcurve`.
-3. `fan <value>` - set the fan power with the value from `1` to `100` and disable auto mode. There is no way to completely disable the fan.
+2. `fan auto` - enable auto speed controller mode, which correlates with fan curve `fcurve`.
+3. `fan <value>` - set the fan power with the value from `1` to `100` and disable auto mode. There is no way to disable the fan.
 Please note that power doesn't correlate with the actual speed linearly.
-4. `fcurve <a> <b> <c>` - set coefficients of the controlling curve `a*x^2 + b*x + c`, where `x` is `abs_max_tec_i/MAX_TEC_I`, a normalized value in range [0,1],
-i.e. the (linear) proportion of current output capacity used, on the channel with the largest current flow. The controlling curve is also clamped to [0,1].
-5. `fcurve default` - restore fan curve coefficients to defaults: `a = 1.0, b = 0.0, c = 0.0`.
+4. `fcurve <a> <b> <c>` - set coefficients of the controlling curve `a*x^2 + b*x + c`, where `x` is `abs_max_tec_i/MAX_TEC_I`, 
+i.e. receives values from 0 to 1 linearly tied to the maximum current. The controlling curve should produce values from 0 to 1,
+as below and beyond values would be substituted by 0 and 1 respectively.
+5. `fcurve default` - restore fan curve settings to defaults: `a = 1.0, b = 0.0, c = 0.0`.

src/channel_state.rs

@@ -2,13 +2,11 @@ use smoltcp::time::{Duration, Instant};
 use uom::si::{
     f64::{
         ElectricPotential,
-        ElectricCurrent,
         ElectricalResistance,
         ThermodynamicTemperature,
         Time,
     },
     electric_potential::volt,
-    electric_current::ampere,
     electrical_resistance::ohm,
     thermodynamic_temperature::degree_celsius,
     time::millisecond,
@@ -31,7 +29,6 @@ pub struct ChannelState {
     /// 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,
@@ -47,7 +44,6 @@ impl ChannelState {
             adc_interval: Duration::from_millis(100),
             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

@@ -20,7 +20,7 @@ use crate::{
     command_handler::JsonBuffer,
     pins,
     steinhart_hart,
-    hw_rev,
+    timer,
 };
 
 pub const CHANNELS: usize = 2;
@@ -29,18 +29,17 @@ pub const R_SENSE: f64 = 0.05;
 const DAC_OUT_V_MAX: f64 = 3.0;
 
 // TODO: -pub
-pub struct Channels<'a> {
+pub struct Channels {
     channel0: Channel<Channel0>,
     channel1: Channel<Channel1>,
     pub adc: ad7172::Adc<pins::AdcSpi, pins::AdcNss>,
     /// stm32f4 integrated adc
     pins_adc: pins::PinsAdc,
     pub pwm: pins::PwmPins,
-    hwrev: &'a hw_rev::HWRev,
 }
 
-impl<'a> Channels<'a> {
-    pub fn new(pins: pins::Pins, hwrev: &'a hw_rev::HWRev) -> Self {
+impl Channels {
+    pub fn new(pins: pins::Pins) -> Self {
         let mut adc = ad7172::Adc::new(pins.adc_spi, pins.adc_nss).unwrap();
         // Feature not used
         adc.set_sync_enable(false).unwrap();
@@ -58,7 +57,7 @@ impl<'a> Channels<'a> {
         let channel1 = Channel::new(pins.channel1, adc_calibration1);
         let pins_adc = pins.pins_adc;
         let pwm = pins.pwm;
-        let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm, hwrev };
+        let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm };
         for channel in 0..CHANNELS {
             channels.calibrate_dac_value(channel);
             channels.set_i(channel, ElectricCurrent::new::<ampere>(0.0));
@@ -96,11 +95,16 @@ impl<'a> Channels<'a> {
         })
     }
 
-    /// calculate the TEC i_set centerpoint
+    /// get the TEC i_set centerpoint
     pub fn get_center(&mut self, channel: usize) -> ElectricPotential {
         match self.channel_state(channel).center {
-            CenterPoint::Vref =>
-                self.read_vref(channel),
+            CenterPoint::Vref => {
+                match channel {
+                    0 => self.channel0.vref_meas,
+                    1 => self.channel1.vref_meas,
+                    _ => unreachable!(),
+                }
+            },
             CenterPoint::Override(center_point) =>
                 ElectricPotential::new::<volt>(center_point.into()),
         }
@@ -113,8 +117,11 @@ impl<'a> Channels<'a> {
     }
 
     pub fn get_i(&mut self, channel: usize) -> ElectricCurrent {
-        let i_set = self.channel_state(channel).i_set;
-        i_set
+        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
     }
 
     /// i_set DAC
@@ -129,19 +136,13 @@ impl<'a> Channels<'a> {
         voltage
     }
 
-    pub fn set_i(&mut self, channel: usize, i_set: ElectricCurrent) -> ElectricCurrent {
-        let vref_meas = match channel.into() {
-            0 => self.channel0.vref_meas,
-            1 => self.channel1.vref_meas,
-            _ => unreachable!(),
-        };
-        let center_point = vref_meas;
+    pub fn set_i(&mut self, channel: usize, i_tec: ElectricCurrent) -> ElectricCurrent {
+        let center_point = self.get_center(channel);
         let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
-        let voltage = i_set * 10.0 * r_sense + center_point;
+        let voltage = i_tec * 10.0 * r_sense + center_point;
         let voltage = self.set_dac(channel, voltage);
-        let i_set = (voltage - center_point) / (10.0 * r_sense);
-        self.channel_state(channel).i_set = i_set;
-        i_set
+        let i_tec = (voltage - center_point) / (10.0 * r_sense);
+        i_tec
     }
 
     pub fn read_dac_feedback(&mut self, channel: usize) -> ElectricPotential {
@@ -166,17 +167,6 @@ impl<'a> Channels<'a> {
         }
     }
 
-    pub fn read_dac_feedback_until_stable(&mut self, channel: usize, tolerance: ElectricPotential) -> ElectricPotential {
-        let mut prev = self.read_dac_feedback(channel);
-        loop {
-            let current = self.read_dac_feedback(channel);
-            if (current - prev).abs() < tolerance {
-                return current;
-            }
-            prev = current;
-        }
-    }
-
     pub fn read_itec(&mut self, channel: usize) -> ElectricPotential {
         match channel {
             0 => {
@@ -262,15 +252,19 @@ impl<'a> Channels<'a> {
     /// thermostat. 
     pub fn calibrate_dac_value(&mut self, channel: usize) {
         let samples = 50;
-        let mut target_voltage = ElectricPotential::new::<volt>(0.0);
-        for _ in 0..samples {
-            target_voltage = target_voltage + self.get_center(channel);
-        }
-        target_voltage = target_voltage / samples as f64;
+        let target_voltage = {
+            let mut target_voltage = ElectricPotential::new::<volt>(0.0);
+            for _ in 0..samples {
+                target_voltage += self.read_vref(channel);
+            }
+            target_voltage /= samples as f64;
+            target_voltage
+        };
         let mut start_value = 1;
         let mut best_error = ElectricPotential::new::<volt>(100.0);
 
         for step in (0..18).rev() {
+            timer::sleep(5);
             let mut prev_value = start_value;
             for value in (start_value..=ad5680::MAX_VALUE).step_by(1 << step) {
                 match channel {
@@ -283,7 +277,14 @@ impl<'a> Channels<'a> {
                     _ => unreachable!(),
                 }
 
-                let dac_feedback = self.read_dac_feedback_until_stable(channel, ElectricPotential::new::<volt>(0.001));
+                let dac_feedback = {
+                    let mut dac_feedback = ElectricPotential::new::<volt>(0.0);
+                    for _ in 0..samples {
+                        dac_feedback += self.read_dac_feedback(channel);
+                    }
+                    dac_feedback /= samples as f64;
+                    dac_feedback
+                };
                 let error = target_voltage - dac_feedback;
                 if error < ElectricPotential::new::<volt>(0.0) {
                     break;
@@ -371,7 +372,7 @@ impl<'a> Channels<'a> {
 
     // Get current passing through TEC
     pub fn get_tec_i(&mut self, channel: usize) -> ElectricCurrent {
-        (self.read_itec(channel) - self.read_vref(channel)) / ElectricalResistance::new::<ohm>(0.4)
+        (self.read_itec(channel) - ElectricPotential::new::<volt>(1.5)) / ElectricalResistance::new::<ohm>(0.4)
     }
 
     // Get voltage across TEC
@@ -429,8 +430,8 @@ impl<'a> Channels<'a> {
 
     fn report(&mut self, channel: usize) -> Report {
         let i_set = self.get_i(channel);
-        let i_tec = if self.hwrev.major > 2 {Some(self.read_itec(channel))} else {None};
-        let tec_i = if self.hwrev.major > 2 {Some(self.get_tec_i(channel))} else {None};
+        let i_tec = self.read_itec(channel);
+        let tec_i = self.get_tec_i(channel);
         let dac_value = self.get_dac(channel);
         let state = self.channel_state(channel);
         let pid_output = ElectricCurrent::new::<ampere>(state.pid.y1);
@@ -524,9 +525,9 @@ impl<'a> Channels<'a> {
         serde_json_core::to_vec(&summaries)
     }
 
-    pub fn current_abs_max_tec_i(&mut self) -> ElectricCurrent {
-        max_by(self.get_tec_i(0).abs(),
-               self.get_tec_i(1).abs(),
+    pub fn current_abs_max_tec_i(&mut self) -> f64 {
+        max_by(self.get_tec_i(0).abs().get::<ampere>(),
+               self.get_tec_i(1).abs().get::<ampere>(),
                |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal))
     }
 }
@@ -543,8 +544,8 @@ pub struct Report {
     i_set: ElectricCurrent,
     dac_value: ElectricPotential,
     dac_feedback: ElectricPotential,
-    i_tec: Option<ElectricPotential>,
-    tec_i: Option<ElectricCurrent>,
+    i_tec: ElectricPotential,
+    tec_i: ElectricCurrent,
     tec_u_meas: ElectricPotential,
     pid_output: ElectricCurrent,
 }

src/command_handler.rs

@@ -207,11 +207,11 @@ impl Handler {
     }
 
     fn set_center_point(socket: &mut TcpSocket, channels: &mut Channels, channel: usize, center: CenterPoint) -> Result<Handler, Error> {
-        let i_set = channels.get_i(channel);
+        let i_tec = channels.get_i(channel);
         let state = channels.channel_state(channel);
         state.center = center;
         if !state.pid_engaged {
-            channels.set_i(channel, i_set);
+            channels.set_i(channel, i_tec);
         }
         send_line(socket, b"{}");
         Ok(Handler::Handled)

src/fan_ctrl.rs

@@ -4,10 +4,7 @@ use stm32f4xx_hal::{
     pwm::{self, PwmChannels},
     pac::TIM8,
 };
-use uom::si::{
-    f64::ElectricCurrent,
-    electric_current::ampere,
-};
+
 use crate::{
     hw_rev::HWSettings,
     command_handler::JsonBuffer,
@@ -53,8 +50,8 @@ impl FanCtrl {
         fan_ctrl
     }
 
-    pub fn cycle(&mut self, abs_max_tec_i: ElectricCurrent) {
-        self.abs_max_tec_i = abs_max_tec_i.get::<ampere>() as f32;
+    pub fn cycle(&mut self, abs_max_tec_i: f32) {
+        self.abs_max_tec_i = abs_max_tec_i;
         if self.fan_auto && self.hw_settings.fan_available {
             let scaled_current = self.abs_max_tec_i / MAX_TEC_I;
             // do not limit upper bound, as it will be limited in the set_pwm()

src/main.rs

@@ -138,7 +138,7 @@ fn main() -> ! {
 
     let mut store = flash_store::store(dp.FLASH);
 
-    let mut channels = Channels::new(pins, &hwrev);
+    let mut channels = Channels::new(pins);
     for c in 0..CHANNELS {
         match store.read_value::<ChannelConfig>(CHANNEL_CONFIG_KEY[c]) {
             Ok(Some(config)) =>
@@ -185,7 +185,7 @@ fn main() -> ! {
                     server.for_each(|_, session| session.set_report_pending(channel.into()));
                 }
 
-                fan_ctrl.cycle(channels.current_abs_max_tec_i());
+                fan_ctrl.cycle(channels.current_abs_max_tec_i() as f32);
 
                 if channels.pid_engaged() {
                     leds.g3.on();