Save i_set into ChannelConfig

- Not respecting the design specs can cause hardware to get stuck in unrecoverable state

README.md

@@ -264,7 +264,6 @@ 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                          |
@@ -272,18 +271,19 @@ 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 noisy without the hardware fix shown in [this PR][https://git.m-labs.hk/M-Labs/thermostat/pulls/105].
+
 ## 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 is available for the thermostat revisions with integrated fan system. For this purpose four commands are available:
+Fan control commands are available for thermostat revisions with an integrated fan system:
 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, 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.
+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.
 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`, 
-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`.
+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`.

src/channel_state.rs

@@ -2,11 +2,13 @@ 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,
@@ -29,6 +31,7 @@ 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,
@@ -44,6 +47,7 @@ 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

@@ -1,5 +1,6 @@
-use core::cmp::max_by;
+use core::{cmp::max_by, marker::PhantomData};
 use heapless::{consts::U2, Vec};
+use num_traits::Zero;
 use serde::{Serialize, Serializer};
 use smoltcp::time::Instant;
 use stm32f4xx_hal::hal;
@@ -18,15 +19,38 @@ use crate::{
     channel_state::ChannelState,
     command_parser::{CenterPoint, PwmPin},
     command_handler::JsonBuffer,
-    pins,
+    pins::{self, Channel0VRef, Channel1VRef},
     steinhart_hart,
 };
 
+pub enum PinsAdcReadTarget {
+    VREF,
+    DacVfb,
+    ITec,
+    VTec,
+}
+
 pub const CHANNELS: usize = 2;
 pub const R_SENSE: f64 = 0.05;
-// DAC chip outputs 0-5v, which is then passed through a resistor dividor to provide 0-3v range
-const DAC_OUT_V_MAX: f64 = 3.0;
 
+// From design specs
+pub const MAX_TEC_I: ElectricCurrent = ElectricCurrent {
+    dimension: PhantomData,
+    units: PhantomData,
+    value: 2.0,
+};
+pub const MAX_TEC_V: ElectricPotential = ElectricPotential {
+    dimension: PhantomData,
+    units: PhantomData,
+    value: 4.0,
+};
+
+// DAC chip outputs 0-5v, which is then passed through a resistor dividor to provide 0-3v range
+const DAC_OUT_V_MAX: ElectricPotential = ElectricPotential {
+    dimension: PhantomData,
+    units: PhantomData,
+    value: 3.0,
+};
 // TODO: -pub
 pub struct Channels {
     channel0: Channel<Channel0>,
@@ -98,7 +122,7 @@ impl Channels {
     pub fn get_center(&mut self, channel: usize) -> ElectricPotential {
         match self.channel_state(channel).center {
             CenterPoint::Vref =>
-                self.read_vref(channel),
+                self.adc_read(channel, PinsAdcReadTarget::VREF, 8),
             CenterPoint::Override(center_point) =>
                 ElectricPotential::new::<volt>(center_point.into()),
         }
@@ -111,16 +135,13 @@ 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
+        let i_set = self.channel_state(channel).i_set;
+        i_set
     }
 
     /// i_set DAC
     fn set_dac(&mut self, channel: usize, voltage: ElectricPotential) -> ElectricPotential {
-        let value = ((voltage / ElectricPotential::new::<volt>(DAC_OUT_V_MAX)).get::<ratio>() * (ad5680::MAX_VALUE as f64)) as u32 ;
+        let value = ((voltage / DAC_OUT_V_MAX).get::<ratio>() * (ad5680::MAX_VALUE as f64)) as u32 ;
         match channel {
             0 => self.channel0.dac.set(value).unwrap(),
             1 => self.channel1.dac.set(value).unwrap(),
@@ -130,7 +151,8 @@ impl Channels {
         voltage
     }
 
-    pub fn set_i(&mut self, channel: usize, i_tec: ElectricCurrent) -> ElectricCurrent {
+    pub fn set_i(&mut self, channel: usize, i_set: ElectricCurrent) -> ElectricCurrent {
+        let i_set = i_set.min(MAX_TEC_I).max(-MAX_TEC_I);
         let vref_meas = match channel.into() {
             0 => self.channel0.vref_meas,
             1 => self.channel1.vref_meas,
@@ -138,38 +160,119 @@ impl Channels {
         };
         let center_point = vref_meas;
         let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
-        let voltage = i_tec * 10.0 * r_sense + center_point;
+        let voltage = i_set * 10.0 * r_sense + center_point;
         let voltage = self.set_dac(channel, voltage);
-        let i_tec = (voltage - center_point) / (10.0 * r_sense);
-        i_tec
+        let i_set = (voltage - center_point) / (10.0 * r_sense);
+        self.channel_state(channel).i_set = i_set;
+        i_set
     }
 
-    pub fn read_dac_feedback(&mut self, channel: usize) -> ElectricPotential {
+    /// AN4073: ADC Reading Dispersion can be reduced through Averaging
+    pub fn adc_read(&mut self, channel: usize, adc_read_target: PinsAdcReadTarget, avg_pt: u16) -> ElectricPotential {
+        let mut sample: u32 = 0;
         match channel {
             0 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel0.dac_feedback_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
+                sample = match adc_read_target {
+                    PinsAdcReadTarget::VREF => {
+                        match &self.channel0.vref_pin {
+                            Channel0VRef::Analog(vref_pin) => {
+                                for _ in (0..avg_pt).rev() {
+                                    sample += self
+                                        .pins_adc
+                                        .convert(vref_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                        as u32;
+                                }
+                                sample / avg_pt as u32
+                            },
+                            Channel0VRef::Disabled(_) => {2048 as u32}
+                        }
+                    }
+                    PinsAdcReadTarget::DacVfb => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel0.dac_feedback_pin,stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                    PinsAdcReadTarget::ITec => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel0.itec_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                    PinsAdcReadTarget::VTec => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel0.tec_u_meas_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                };
+                let mv = self.pins_adc.sample_to_millivolts(sample as u16);
                 ElectricPotential::new::<millivolt>(mv as f64)
             }
             1 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel1.dac_feedback_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
+                sample = match adc_read_target {
+                    PinsAdcReadTarget::VREF => {
+                        match &self.channel1.vref_pin {
+                            Channel1VRef::Analog(vref_pin) => {
+                                for _ in (0..avg_pt).rev() {
+                                    sample += self
+                                        .pins_adc
+                                        .convert(vref_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                        as u32;
+                                }
+                                sample / avg_pt as u32
+                            },
+                            Channel1VRef::Disabled(_) => {2048 as u32}
+                        }
+                    }
+                    PinsAdcReadTarget::DacVfb => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel1.dac_feedback_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                    PinsAdcReadTarget::ITec => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel1.itec_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                    PinsAdcReadTarget::VTec => {
+                        for _ in (0..avg_pt).rev() {
+                            sample += self
+                                .pins_adc
+                                .convert(&self.channel1.tec_u_meas_pin, stm32f4xx_hal::adc::config::SampleTime::Cycles_480)
+                                as u32;
+                        }
+                        sample / avg_pt as u32
+                    }
+                };
+                let mv = self.pins_adc.sample_to_millivolts(sample as u16);
                 ElectricPotential::new::<millivolt>(mv as f64)
             }
-            _ => unreachable!(),
+            _ => unreachable!()
         }
     }
 
     pub fn read_dac_feedback_until_stable(&mut self, channel: usize, tolerance: ElectricPotential) -> ElectricPotential {
-        let mut prev = self.read_dac_feedback(channel);
+        let mut prev = self.adc_read(channel, PinsAdcReadTarget::DacVfb, 1);
         loop {
-            let current = self.read_dac_feedback(channel);
+            let current = self.adc_read(channel, PinsAdcReadTarget::DacVfb, 1);
             if (current - prev).abs() < tolerance {
                 return current;
             }
@@ -177,73 +280,6 @@ impl Channels {
         }
     }
 
-    pub fn read_itec(&mut self, channel: usize) -> ElectricPotential {
-        match channel {
-            0 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel0.itec_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            1 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel1.itec_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            _ => unreachable!(),
-        }
-    }
-
-    /// should be 1.5V
-    pub fn read_vref(&mut self, channel: usize) -> ElectricPotential {
-        match channel {
-            0 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel0.vref_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            1 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel1.vref_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            _ => unreachable!(),
-        }
-    }
-
-    pub fn read_tec_u_meas(&mut self, channel: usize) -> ElectricPotential {
-        match channel {
-            0 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel0.tec_u_meas_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            1 => {
-                let sample = self.pins_adc.convert(
-                    &self.channel1.tec_u_meas_pin,
-                    stm32f4xx_hal::adc::config::SampleTime::Cycles_480
-                );
-                let mv = self.pins_adc.sample_to_millivolts(sample);
-                ElectricPotential::new::<millivolt>(mv as f64)
-            }
-            _ => unreachable!(),
-        }
-    }
-
     /// Calibrates the DAC output to match vref of the MAX driver to reduce zero-current offset of the MAX driver output.
     ///
     /// The thermostat DAC applies a control voltage signal to the CTLI pin of MAX driver chip to control its output current.
@@ -291,7 +327,7 @@ impl Channels {
                     best_error = error;
                     start_value = prev_value;
 
-                    let vref = (value as f64 / ad5680::MAX_VALUE as f64) * ElectricPotential::new::<volt>(DAC_OUT_V_MAX);
+                    let vref = (value as f64 / ad5680::MAX_VALUE as f64) * DAC_OUT_V_MAX;
                     match channel {
                         0 => self.channel0.vref_meas = vref,
                         1 => self.channel1.vref_meas = vref,
@@ -351,32 +387,32 @@ impl Channels {
         }
     }
 
-    pub fn get_max_v(&mut self, channel: usize) -> ElectricPotential {
+    pub fn get_max_v(&mut self, channel: usize) -> (ElectricPotential, ElectricPotential) {
         let max = 4.0 * ElectricPotential::new::<volt>(3.3);
         let duty = self.get_pwm(channel, PwmPin::MaxV);
-        duty * max
+        (duty * max, MAX_TEC_V)
     }
 
     pub fn get_max_i_pos(&mut self, channel: usize) -> (ElectricCurrent, ElectricCurrent) {
         let max = ElectricCurrent::new::<ampere>(3.0);
         let duty = self.get_pwm(channel, PwmPin::MaxIPos);
-        (duty * max, max)
+        (duty * max, MAX_TEC_I)
     }
 
     pub fn get_max_i_neg(&mut self, channel: usize) -> (ElectricCurrent, ElectricCurrent) {
         let max = ElectricCurrent::new::<ampere>(3.0);
         let duty = self.get_pwm(channel, PwmPin::MaxINeg);
-        (duty * max, max)
+        (duty * max, MAX_TEC_I)
     }
 
     // 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.adc_read(channel, PinsAdcReadTarget::ITec, 16) - self.adc_read(channel, PinsAdcReadTarget::VREF, 16)) / ElectricalResistance::new::<ohm>(0.4)
     }
 
     // Get voltage across TEC
     pub fn get_tec_v(&mut self, channel: usize) -> ElectricPotential {
-        (self.read_tec_u_meas(channel) - ElectricPotential::new::<volt>(1.5)) * 4.0
+        (self.adc_read(channel, PinsAdcReadTarget::VTec, 16) - ElectricPotential::new::<volt>(1.5)) * 4.0
     }
 
     fn set_pwm(&mut self, channel: usize, pin: PwmPin, duty: f64) -> f64 {
@@ -408,28 +444,28 @@ impl Channels {
 
     pub fn set_max_v(&mut self, channel: usize, max_v: ElectricPotential) -> (ElectricPotential, ElectricPotential) {
         let max = 4.0 * ElectricPotential::new::<volt>(3.3);
-        let duty = (max_v / max).get::<ratio>();
+        let duty = (max_v.min(MAX_TEC_V).max(ElectricPotential::zero()) / max).get::<ratio>();
         let duty = self.set_pwm(channel, PwmPin::MaxV, duty);
         (duty * max, max)
     }
 
     pub fn set_max_i_pos(&mut self, channel: usize, max_i_pos: ElectricCurrent) -> (ElectricCurrent, ElectricCurrent) {
         let max = ElectricCurrent::new::<ampere>(3.0);
-        let duty = (max_i_pos / max).get::<ratio>();
+        let duty = (max_i_pos.min(MAX_TEC_I).max(ElectricCurrent::zero()) / max).get::<ratio>();
         let duty = self.set_pwm(channel, PwmPin::MaxIPos, duty);
         (duty * max, max)
     }
 
     pub fn set_max_i_neg(&mut self, channel: usize, max_i_neg: ElectricCurrent) -> (ElectricCurrent, ElectricCurrent) {
         let max = ElectricCurrent::new::<ampere>(3.0);
-        let duty = (max_i_neg / max).get::<ratio>();
+        let duty = (max_i_neg.min(MAX_TEC_I).max(ElectricCurrent::zero()) / max).get::<ratio>();
         let duty = self.set_pwm(channel, PwmPin::MaxINeg, duty);
         (duty * max, max)
     }
 
     fn report(&mut self, channel: usize) -> Report {
         let i_set = self.get_i(channel);
-        let i_tec = self.read_itec(channel);
+        let i_tec = self.adc_read(channel, PinsAdcReadTarget::ITec, 16);
         let tec_i = self.get_tec_i(channel);
         let dac_value = self.get_dac(channel);
         let state = self.channel_state(channel);
@@ -445,7 +481,7 @@ impl Channels {
             pid_engaged: state.pid_engaged,
             i_set,
             dac_value,
-            dac_feedback: self.read_dac_feedback(channel),
+            dac_feedback: self.adc_read(channel, PinsAdcReadTarget::DacVfb, 1),
             i_tec,
             tec_i,
             tec_u_meas: self.get_tec_v(channel),
@@ -482,8 +518,8 @@ impl Channels {
         PwmSummary {
             channel,
             center: CenterPointJson(self.channel_state(channel).center.clone()),
-            i_set: (self.get_i(channel), ElectricCurrent::new::<ampere>(3.0)).into(),
-            max_v: (self.get_max_v(channel), ElectricPotential::new::<volt>(5.0)).into(),
+            i_set: (self.get_i(channel), MAX_TEC_I).into(),
+            max_v: self.get_max_v(channel).into(),
             max_i_pos: self.get_max_i_pos(channel).into(),
             max_i_neg: self.get_max_i_neg(channel).into(),
         }
@@ -524,9 +560,9 @@ impl Channels {
         serde_json_core::to_vec(&summaries)
     }
 
-    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>(),
+    pub fn current_abs_max_tec_i(&mut self) -> ElectricCurrent {
+        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

@@ -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_tec = channels.get_i(channel);
+        let i_set = channels.get_i(channel);
         let state = channels.channel_state(channel);
         state.center = center;
         if !state.pid_engaged {
-            channels.set_i(channel, i_tec);
+            channels.set_i(channel, i_set);
         }
         send_line(socket, b"{}");
         Ok(Handler::Handled)

src/config.rs

@@ -1,3 +1,4 @@
+use num_traits::Zero;
 use serde::{Serialize, Deserialize};
 use uom::si::{
     electric_potential::volt,
@@ -18,6 +19,7 @@ pub struct ChannelConfig {
     pid: pid::Parameters,
     pid_target: f32,
     pid_engaged: bool,
+    i_set: ElectricCurrent,
     sh: steinhart_hart::Parameters,
     pwm: PwmLimits,
     /// uses variant `PostFilter::Invalid` instead of `None` to save space
@@ -33,11 +35,17 @@ impl ChannelConfig {
             .unwrap_or(PostFilter::Invalid);
 
         let state = channels.channel_state(channel);
+        let i_set = if state.pid_engaged { 
+            ElectricCurrent::zero() 
+        } else { 
+            state.i_set 
+        };
         ChannelConfig {
             center: state.center.clone(),
             pid: state.pid.parameters.clone(),
             pid_target: state.pid.target as f32,
             pid_engaged: state.pid_engaged,
+            i_set: i_set,
             sh: state.sh.clone(),
             pwm,
             adc_postfilter,
@@ -59,6 +67,7 @@ impl ChannelConfig {
             adc_postfilter => Some(adc_postfilter),
         };
         let _ = channels.adc.set_postfilter(channel as u8, adc_postfilter);
+        let _ = channels.set_i(channel, self.i_set);
     }
 }
 
@@ -71,7 +80,7 @@ struct PwmLimits {
 
 impl PwmLimits {
     pub fn new(channels: &mut Channels, channel: usize) -> Self {
-        let max_v = channels.get_max_v(channel);
+        let (max_v, _) = channels.get_max_v(channel);
         let (max_i_pos, _) = channels.get_max_i_pos(channel);
         let (max_i_neg, _) = channels.get_max_i_neg(channel);
         PwmLimits {

src/fan_ctrl.rs

@@ -4,17 +4,18 @@ use stm32f4xx_hal::{
     pwm::{self, PwmChannels},
     pac::TIM8,
 };
-
+use uom::si::{
+    f64::ElectricCurrent,
+    electric_current::ampere,
+};
 use crate::{
     hw_rev::HWSettings,
     command_handler::JsonBuffer,
+    channels::MAX_TEC_I,
 };
 
 pub type FanPin = PwmChannels<TIM8, pwm::C4>;
 
-// as stated in the schematics
-const MAX_TEC_I: f32 = 3.0;
-
 const MAX_USER_FAN_PWM: f32 = 100.0;
 const MIN_USER_FAN_PWM: f32 = 1.0;
 
@@ -50,10 +51,10 @@ impl FanCtrl {
         fan_ctrl
     }
 
-    pub fn cycle(&mut self, abs_max_tec_i: f32) {
-        self.abs_max_tec_i = abs_max_tec_i;
+    pub fn cycle(&mut self, abs_max_tec_i: ElectricCurrent) {
+        self.abs_max_tec_i = abs_max_tec_i.get::<ampere>() as f32;
         if self.fan_auto && self.hw_settings.fan_available {
-            let scaled_current = self.abs_max_tec_i / MAX_TEC_I;
+            let scaled_current = self.abs_max_tec_i / MAX_TEC_I.get::<ampere>() as f32;
             // do not limit upper bound, as it will be limited in the set_pwm()
             let pwm = (MAX_USER_FAN_PWM * (scaled_current * (scaled_current * self.k_a + self.k_b) + self.k_c)) as u32;
             self.set_pwm(pwm);

src/main.rs

@@ -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() as f32);
+                fan_ctrl.cycle(channels.current_abs_max_tec_i());
 
                 if channels.pid_engaged() {
                     leds.g3.on();

src/pid.rs

@@ -54,15 +54,13 @@ impl Controller {
     //       + x0 * (kp + ki + kd)
     //       - x1 * (kp + 2kd)
     //       + x2 * kd
-    //       + kp * (u0 - u1)
     // y0  = clip(y0', ymin, ymax)
     pub fn update(&mut self, input: f64) -> f64 {
         
         let mut output: f64 = self.y1 - self.target * f64::from(self.parameters.ki)
                             + input * f64::from(self.parameters.kp + self.parameters.ki + self.parameters.kd)
                             - self.x1 * f64::from(self.parameters.kp + 2.0 * self.parameters.kd)
-                            + self.x2 * f64::from(self.parameters.kd)
-                            + f64::from(self.parameters.kp) * (self.target - self.u1);
+                            + self.x2 * f64::from(self.parameters.kd);
         if output < self.parameters.output_min.into() {
             output = self.parameters.output_min.into();
         }

src/pins.rs

@@ -66,21 +66,31 @@ pub trait ChannelPins {
     type TecUMeasPin;
 }
 
+pub enum Channel0VRef {
+    Analog(PA0<Analog>),
+    Disabled(PA0<Input<Floating>>),
+}
+
 impl ChannelPins for Channel0 {
     type DacSpi = Dac0Spi;
     type DacSync = PE4<Output<PushPull>>;
     type Shdn = PE10<Output<PushPull>>;
-    type VRefPin = PA0<Analog>;
+    type VRefPin = Channel0VRef;
     type ItecPin = PA6<Analog>;
     type DacFeedbackPin = PA4<Analog>;
     type TecUMeasPin = PC2<Analog>;
 }
 
+pub enum Channel1VRef {
+    Analog(PA3<Analog>),
+    Disabled(PA3<Input<Floating>>),
+}
+
 impl ChannelPins for Channel1 {
     type DacSpi = Dac1Spi;
     type DacSync = PF6<Output<PushPull>>;
     type Shdn = PE15<Output<PushPull>>;
-    type VRefPin = PA3<Analog>;
+    type VRefPin = Channel1VRef;
     type ItecPin = PB0<Analog>;
     type DacFeedbackPin = PA5<Analog>;
     type TecUMeasPin = PC3<Analog>;
@@ -150,13 +160,17 @@ impl Pins {
             gpioe.pe13, gpioe.pe14
         );
 
+        let hwrev = HWRev::detect_hw_rev(&HWRevPins {hwrev0: gpiod.pd0, hwrev1: gpiod.pd1,
+            hwrev2: gpiod.pd2, hwrev3: gpiod.pd3});
+        let hw_settings = hwrev.settings();
+
         let (dac0_spi, dac0_sync) = Self::setup_dac0(
             clocks, spi4,
             gpioe.pe2, gpioe.pe4, gpioe.pe6
         );
         let mut shdn0 = gpioe.pe10.into_push_pull_output();
         let _ = shdn0.set_low();
-        let vref0_pin = gpioa.pa0.into_analog();
+        let vref0_pin = if hwrev.major > 2 {Channel0VRef::Analog(gpioa.pa0.into_analog())} else {Channel0VRef::Disabled(gpioa.pa0)};
         let itec0_pin = gpioa.pa6.into_analog();
         let dac_feedback0_pin = gpioa.pa4.into_analog();
         let tec_u_meas0_pin = gpioc.pc2.into_analog();
@@ -176,7 +190,7 @@ impl Pins {
         );
         let mut shdn1 = gpioe.pe15.into_push_pull_output();
         let _ = shdn1.set_low();
-        let vref1_pin = gpioa.pa3.into_analog();
+        let vref1_pin = if hwrev.major > 2 {Channel1VRef::Analog(gpioa.pa3.into_analog())} else {Channel1VRef::Disabled(gpioa.pa3)};
         let itec1_pin = gpiob.pb0.into_analog();
         let dac_feedback1_pin = gpioa.pa5.into_analog();
         let tec_u_meas1_pin = gpioc.pc3.into_analog();
@@ -198,10 +212,6 @@ impl Pins {
             channel1,
         };
 
-        let hwrev = HWRev::detect_hw_rev(&HWRevPins {hwrev0: gpiod.pd0, hwrev1: gpiod.pd1,
-            hwrev2: gpiod.pd2, hwrev3: gpiod.pd3});
-        let hw_settings = hwrev.settings();
-
         let leds = Leds::new(gpiod.pd9, gpiod.pd10.into_push_pull_output(), gpiod.pd11.into_push_pull_output());
 
         let eeprom_scl = gpiob.pb8.into_alternate().set_open_drain();