Show polarity in pwm command

Effectively flips all values related to the directionality of current
through the TEC, including current maximums. The reversed status is
stored in the flash store and will be loaded on reset once saved.

The command is "pwm <ch> polarity <normal/reversed>", where the "normal"
polarity is indicated by the front panel markings.

This is needed for IDC cable connections to the Sinara 5432 DAC
"Zotino", since the TEC pins of the 10-pin connector on the Thermostat
and Zotino have opposite polarities.

Polarity command

README.md

@@ -93,13 +93,16 @@ Send commands as simple text string terminated by `\n`. Responses are
 formatted as line-delimited JSON.
 
 | Syntax                                     | Function                                                                      |
-|----------------------------------|-------------------------------------------------------------------------------|
+|------------------------------------------- |-------------------------------------------------------------------------------|
 | `report`                                   | Show current input                                                            |
+| `report mode`                              | Show current report mode                                                      |
+| `report mode <off/on>`                     | Set report mode                                                               |
 | `pwm`                                      | Show current PWM settings                                                     |
 | `pwm <0/1> max_i_pos <amp>`                | Set maximum positive output current                                           |
 | `pwm <0/1> max_i_neg <amp>`                | Set maximum negative output current                                           |
 | `pwm <0/1> max_v <volt>`                   | Set maximum output voltage                                                    |
 | `pwm <0/1> i_set <amp>`                    | Disengage PID, set fixed output current                                       |
+| `pwm <0/1> polarity <normal/reversed>`     | Set output current polarity, with 'normal' being the front panel polarity     |
 | `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                           |
@@ -182,6 +185,8 @@ postfilter rate can be tuned with the `postfilter` command.
 
 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.
 
+If the Thermostat is used for temperature control with the Sinara 5432 DAC "Zotino", and is connected via an IDC cable, the TEC polarity may need to be reversed with the `pwm <ch> polarity reversed` TCP command.
+
 Testing heat flow direction with a low set current is recommended before installation of the TEC module.
 
 ### Limits

pytec/pytec/client.py

@@ -57,12 +57,14 @@ class Client:
               'max_i_neg': {'max': 3.0, 'value': 3.0},
               'max_v': {'max': 5.988, 'value': 5.988},
               'max_i_pos': {'max': 3.0, 'value': 3.0}},
+              'polarity': 'normal',
              {'channel': 1,
               'center': 'vref',
               'i_set': {'max': 2.9802790335151985, 'value': -0.02002179650216762},
               'max_i_neg': {'max': 3.0, 'value': 3.0},
               'max_v': {'max': 5.988, 'value': 5.988},
               'max_i_pos': {'max': 3.0, 'value': 3.0}}
+              'polarity': 'normal',
             ]
         """
         return self._get_conf("pwm")

src/channel_state.rs

@@ -17,7 +17,7 @@ use crate::{
     ad7172,
     pid,
     steinhart_hart as sh,
-    command_parser::CenterPoint,
+    command_parser::{CenterPoint, Polarity},
 };
 
 const R_INNER: f64 = 2.0 * 5100.0;
@@ -35,6 +35,7 @@ pub struct ChannelState {
     pub pid_engaged: bool,
     pub pid: pid::Controller,
     pub sh: sh::Parameters,
+    pub polarity: Polarity,
 }
 
 impl ChannelState {
@@ -51,6 +52,7 @@ impl ChannelState {
             pid_engaged: false,
             pid: pid::Controller::new(pid::Parameters::default()),
             sh: sh::Parameters::default(),
+            polarity: Polarity::Normal,
         }
     }
 

src/channels.rs

@@ -17,7 +17,7 @@ use crate::{
     ad7172,
     channel::{Channel, Channel0, Channel1},
     channel_state::ChannelState,
-    command_parser::{CenterPoint, PwmPin},
+    command_parser::{CenterPoint, PwmPin, Polarity},
     command_handler::JsonBuffer,
     pins::{self, Channel0VRef, Channel1VRef},
     steinhart_hart,
@@ -158,6 +158,11 @@ impl Channels {
 
     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);
+        self.channel_state(channel).i_set = i_set;
+        let negate = match self.channel_state(channel).polarity {
+            Polarity::Normal => 1.0,
+            Polarity::Reversed => -1.0,
+        };
         let vref_meas = match channel.into() {
             0 => self.channel0.vref_meas,
             1 => self.channel1.vref_meas,
@@ -165,10 +170,9 @@ impl Channels {
         };
         let center_point = vref_meas;
         let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
-        let voltage = i_set * 10.0 * r_sense + center_point;
+        let voltage = negate * i_set * 10.0 * r_sense + center_point;
         let voltage = self.set_dac(channel, voltage);
-        let i_set = (voltage - center_point) / (10.0 * r_sense);
+        let i_set = negate * (voltage - center_point) / (10.0 * r_sense);
-        self.channel_state(channel).i_set = i_set;
         i_set
     }
 
@@ -386,18 +390,28 @@ impl Channels {
     }
 
     pub fn get_max_i_pos(&mut self, channel: usize) -> (ElectricCurrent, ElectricCurrent) {
-        let duty = self.get_pwm(channel, PwmPin::MaxIPos);
+        let duty = match self.channel_state(channel).polarity {
+            Polarity::Normal => self.get_pwm(channel, PwmPin::MaxIPos),
+            Polarity::Reversed => self.get_pwm(channel, PwmPin::MaxINeg),
+        };
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, MAX_TEC_I)
     }
 
     pub fn get_max_i_neg(&mut self, channel: usize) -> (ElectricCurrent, ElectricCurrent) {
-        let duty = self.get_pwm(channel, PwmPin::MaxINeg);
+        let duty = match self.channel_state(channel).polarity {
+            Polarity::Normal => self.get_pwm(channel, PwmPin::MaxINeg),
+            Polarity::Reversed => self.get_pwm(channel, PwmPin::MaxIPos),
+        };
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, MAX_TEC_I)
     }
 
     // Get current passing through TEC
     pub fn get_tec_i(&mut self, channel: usize) -> ElectricCurrent {
-        (self.adc_read(channel, PinsAdcReadTarget::ITec, 16) - self.adc_read(channel, PinsAdcReadTarget::VREF, 16)) / ElectricalResistance::new::<ohm>(0.4)
+        let tec_i = (self.adc_read(channel, PinsAdcReadTarget::ITec, 16) - self.adc_read(channel, PinsAdcReadTarget::VREF, 16)) / ElectricalResistance::new::<ohm>(0.4);
+        match self.channel_state(channel).polarity {
+            Polarity::Normal => tec_i,
+            Polarity::Reversed => -tec_i,
+        }
     }
 
     // Get voltage across TEC
@@ -442,17 +456,36 @@ impl Channels {
     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.min(MAX_TEC_I).max(ElectricCurrent::zero()) / MAX_TEC_I_DUTY_TO_CURRENT_RATE).get::<ratio>();
-        let duty = self.set_pwm(channel, PwmPin::MaxIPos, duty);
+        let duty = match self.channel_state(channel).polarity {
+            Polarity::Normal => self.set_pwm(channel, PwmPin::MaxIPos, duty),
+            Polarity::Reversed => self.set_pwm(channel, PwmPin::MaxINeg, duty),
+        };
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, 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.min(MAX_TEC_I).max(ElectricCurrent::zero()) / MAX_TEC_I_DUTY_TO_CURRENT_RATE).get::<ratio>();
-        let duty = self.set_pwm(channel, PwmPin::MaxINeg, duty);
+        let duty = match self.channel_state(channel).polarity {
+            Polarity::Normal => self.set_pwm(channel, PwmPin::MaxINeg, duty),
+            Polarity::Reversed => self.set_pwm(channel, PwmPin::MaxIPos, duty),
+        };
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, max)
     }
 
+    pub fn set_polarity(&mut self, channel: usize, polarity: Polarity) {
+        if self.channel_state(channel).polarity != polarity {
+            let i_set = self.channel_state(channel).i_set;
+            let max_i_pos = self.get_max_i_pos(channel).0;
+            let max_i_neg = self.get_max_i_neg(channel).0;
+            self.channel_state(channel).polarity = polarity;
+
+            self.set_i(channel, i_set);
+            self.set_max_i_pos(channel, max_i_pos);
+            self.set_max_i_neg(channel, max_i_neg);
+        }
+    }
+
     fn report(&mut self, channel: usize) -> Report {
         let i_set = self.get_i(channel);
         let i_tec = self.adc_read(channel, PinsAdcReadTarget::ITec, 16);
@@ -512,6 +545,7 @@ impl Channels {
             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(),
+            polarity: PolarityJson(self.channel_state(channel).polarity.clone()),
         }
     }
 
@@ -593,6 +627,21 @@ impl Serialize for CenterPointJson {
     }
 }
 
+pub struct PolarityJson(Polarity);
+
+// used in JSON encoding, not for config
+impl Serialize for PolarityJson {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(match self.0 {
+            Polarity::Normal => "normal",
+            Polarity::Reversed => "reversed",
+        })
+    }
+}
+
 #[derive(Serialize)]
 pub struct PwmSummaryField<T: Serialize> {
     value: T,
@@ -613,6 +662,7 @@ pub struct PwmSummary {
     max_v: PwmSummaryField<ElectricPotential>,
     max_i_pos: PwmSummaryField<ElectricCurrent>,
     max_i_neg: PwmSummaryField<ElectricCurrent>,
+    polarity: PolarityJson,
 }
 
 #[derive(Serialize)]

src/command_handler.rs

@@ -11,7 +11,8 @@ use super::{
         CenterPoint, 
         PidParameter, 
         PwmPin, 
-        ShParameter
+        ShParameter,
+        Polarity
     },
     ad7172,
     CHANNEL_CONFIG_KEY,
@@ -170,6 +171,12 @@ impl Handler {
         Ok(Handler::Handled)
     }
 
+    fn set_polarity(socket: &mut TcpSocket, channels: &mut Channels, channel: usize, polarity: Polarity) -> Result<Handler, Error> {
+        channels.set_polarity(channel, polarity);
+        send_line(socket, b"{}");
+        Ok(Handler::Handled)
+    }
+
     fn set_pwm (socket: &mut TcpSocket, channels: &mut Channels, channel: usize, pin: PwmPin, value: f64) -> Result<Handler, Error> {
         match pin {
             PwmPin::ISet => {
@@ -411,6 +418,7 @@ impl Handler {
             Command::Show(ShowCommand::PostFilter) => Handler::show_post_filter(socket, channels),
             Command::Show(ShowCommand::Ipv4) => Handler::show_ipv4(socket, ipv4_config),
             Command::PwmPid { channel } => Handler::engage_pid(socket, channels, channel),
+            Command::PwmPolarity { channel, polarity } => Handler::set_polarity(socket, channels, channel, polarity),
             Command::Pwm { channel, pin, value } => Handler::set_pwm(socket, channels, channel, pin, value),
             Command::CenterPoint { channel, center } => Handler::set_center_point(socket, channels, channel, center),
             Command::Pid { channel, parameter, value } => Handler::set_pid(socket, channels, channel, parameter, value),

src/command_parser.rs

@@ -135,6 +135,12 @@ pub enum CenterPoint {
     Override(f32),
 }
 
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum Polarity {
+    Normal,
+    Reversed,
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Command {
     Quit,
@@ -157,6 +163,10 @@ pub enum Command {
     PwmPid {
         channel: usize,
     },
+    PwmPolarity {
+        channel: usize,
+        polarity: Polarity,
+    },
     CenterPoint {
         channel: usize,
         center: CenterPoint,
@@ -297,6 +307,18 @@ fn pwm_pid(input: &[u8]) -> IResult<&[u8], ()> {
     value((), tag("pid"))(input)
 }
 
+fn pwm_polarity(input: &[u8]) -> IResult<&[u8], Polarity> {
+    preceded(
+        tag("polarity"),
+        preceded(
+            whitespace,
+            alt((value(Polarity::Normal, tag("normal")),
+                 value(Polarity::Reversed, tag("reversed"))
+            ))
+        )
+    )(input)
+}
+
 fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     let (input, _) = tag("pwm")(input)?;
     alt((
@@ -309,6 +331,10 @@ fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
                     let (input, ()) = pwm_pid(input)?;
                     Ok((input, Ok(Command::PwmPid { channel })))
                 },
+                |input| {
+                    let (input, polarity) = pwm_polarity(input)?;
+                    Ok((input, Ok(Command::PwmPolarity { channel, polarity })))
+                },
                 |input| {
                     let (input, config) = pwm_setup(input)?;
                     match config {

src/config.rs

@@ -8,7 +8,7 @@ use uom::si::{
 use crate::{
     ad7172::PostFilter,
     channels::Channels,
-    command_parser::CenterPoint,
+    command_parser::{CenterPoint, Polarity},
     pid,
     steinhart_hart,
 };
@@ -20,6 +20,7 @@ pub struct ChannelConfig {
     pid_target: f32,
     pid_engaged: bool,
     i_set: ElectricCurrent,
+    polarity: Polarity,
     sh: steinhart_hart::Parameters,
     pwm: PwmLimits,
     /// uses variant `PostFilter::Invalid` instead of `None` to save space
@@ -45,7 +46,8 @@ impl ChannelConfig {
             pid: state.pid.parameters.clone(),
             pid_target: state.pid.target as f32,
             pid_engaged: state.pid_engaged,
-            i_set: i_set,
+            i_set,
+            polarity: state.polarity.clone(),
             sh: state.sh.clone(),
             pwm,
             adc_postfilter,
@@ -68,6 +70,7 @@ impl ChannelConfig {
         };
         let _ = channels.adc.set_postfilter(channel as u8, adc_postfilter);
         let _ = channels.set_i(channel, self.i_set);
+        channels.set_polarity(channel, self.polarity.clone());
     }
 }