README: Document swap status in report

Signed-off-by: Egor Savkin <es@m-labs.hk>

README.md

@@ -95,7 +95,7 @@ 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                                                               |
@@ -104,6 +104,7 @@ formatted as line-delimited JSON.
 | `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_swapped <false/true>` | Swap output current polarity on channel                                       |
 | `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                           |
@@ -263,6 +264,7 @@ with the following keys.
 | `sens`            | Ohms            | Thermistor resistance derived from `adc`                           |
 | `temperature`     | Degrees Celsius | Steinhart-Hart conversion result derived from `sens`               |
 | `pid_engaged`     | Boolean         | `true` if in closed-loop mode                                      |
+| `current_swapped` | Boolean         | `true` if TEC current direction is swapped relative to front panel |
 | `i_set`           | Amperes         | TEC output current                                                 |
 | `dac_value`       | Volts           | AD5680 output derived from `i_set`                                 |
 | `dac_feedback`    | Volts           | ADC measurement of the AD5680 output                               |

src/channel_state.rs

@@ -35,6 +35,7 @@ pub struct ChannelState {
     pub pid_engaged: bool,
     pub pid: pid::Controller,
     pub sh: sh::Parameters,
+    pub polarity_swapped: bool,
 }
 
 impl ChannelState {
@@ -51,6 +52,7 @@ impl ChannelState {
             pid_engaged: false,
             pid: pid::Controller::new(pid::Parameters::default()),
             sh: sh::Parameters::default(),
+            polarity_swapped: false,
         }
     }
 

src/channels.rs

@@ -154,6 +154,12 @@ 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 = if self.channel_state(channel).polarity_swapped {
+            -1.0
+        } else {
+            1.0
+        };
         let vref_meas = match channel.into() {
             0 => self.channel0.vref_meas,
             1 => self.channel1.vref_meas,
@@ -161,10 +167,9 @@ 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);
-        self.channel_state(channel).i_set = i_set;
+        let i_set = negate * (voltage - center_point) / (10.0 * r_sense);
         i_set
     }
 
@@ -386,19 +391,32 @@ impl Channels {
 
     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);
+        let duty = if self.channel_state(channel).polarity_swapped {
+            self.get_pwm(channel, PwmPin::MaxINeg)
+        } else {
+            self.get_pwm(channel, PwmPin::MaxIPos)
+        };
         (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);
+        let duty = if self.channel_state(channel).polarity_swapped {
+            self.get_pwm(channel, PwmPin::MaxIPos)
+        } else {
+            self.get_pwm(channel, PwmPin::MaxINeg)
+        };
         (duty * max, 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);
+        if self.channel_state(channel).polarity_swapped {
+            -tec_i
+        } else {
+            tec_i
+        }
     }
 
     // Get voltage across TEC
@@ -443,17 +461,38 @@ 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).get::<ratio>();
-        let duty = self.set_pwm(channel, PwmPin::MaxIPos, duty);
+        let duty = if self.channel_state(channel).polarity_swapped {
+            self.set_pwm(channel, PwmPin::MaxINeg, duty)
+        } else {
+            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.min(MAX_TEC_I).max(ElectricCurrent::zero()) / max).get::<ratio>();
-        let duty = self.set_pwm(channel, PwmPin::MaxINeg, duty);
+        let duty = if self.channel_state(channel).polarity_swapped {
+            self.set_pwm(channel, PwmPin::MaxIPos, duty)
+        } else {
+            self.set_pwm(channel, PwmPin::MaxINeg, duty)
+        };
         (duty * max, max)
     }
 
+    pub fn swap_polarity(&mut self, channel: usize, swapped: bool) {
+        if self.channel_state(channel).polarity_swapped != swapped {
+            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_swapped = swapped;
+            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);
@@ -470,6 +509,7 @@ impl Channels {
             temperature: state.get_temperature()
                 .map(|temperature| temperature.get::<degree_celsius>()),
             pid_engaged: state.pid_engaged,
+            current_swapped: state.polarity_swapped,
             i_set,
             dac_value,
             dac_feedback: self.adc_read(channel, PinsAdcReadTarget::DacVfb, 1),
@@ -568,6 +608,7 @@ pub struct Report {
     sens: Option<ElectricalResistance>,
     temperature: Option<f64>,
     pid_engaged: bool,
+    current_swapped: bool,
     i_set: ElectricCurrent,
     dac_value: ElectricPotential,
     dac_feedback: ElectricPotential,

src/command_handler.rs

@@ -181,6 +181,12 @@ impl Handler {
         Ok(Handler::Handled)
     }
 
+    fn swap_polarity (socket: &mut TcpSocket, channels: &mut Channels, channel: usize, swapped: bool) -> Result<Handler, Error> {
+        channels.swap_polarity(channel, swapped);
+        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 => {
@@ -424,6 +430,7 @@ 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::PwmPolaritySwapped { channel, swapped } => Handler::swap_polarity(socket, channels, channel, swapped),
             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

@@ -159,6 +159,10 @@ pub enum Command {
     PwmPid {
         channel: usize,
     },
+    PwmPolaritySwapped {
+        channel: usize,
+        swapped: bool,
+    },
     CenterPoint {
         channel: usize,
         center: CenterPoint,
@@ -239,6 +243,12 @@ fn off_on(input: &[u8]) -> IResult<&[u8], bool> {
     ))(input)
 }
 
+fn boolean(input: &[u8]) -> IResult<&[u8], bool> {
+    alt((value(false, tag("false")),
+         value(true, tag("true"))
+    ))(input)
+}
+
 fn channel(input: &[u8]) -> IResult<&[u8], usize> {
     map(one_of("01"), |c| (c as usize) - ('0' as usize))(input)
 }
@@ -321,6 +331,16 @@ fn pwm_pid(input: &[u8]) -> IResult<&[u8], ()> {
     value((), tag("pid"))(input)
 }
 
+fn pwm_polarity_swapped(input: &[u8]) -> IResult<&[u8], bool> {
+    preceded(
+        tag("polarity_swapped"),
+        preceded(
+            whitespace,
+            boolean,
+        )
+    )(input)
+}
+
 fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     let (input, _) = tag("pwm")(input)?;
     alt((
@@ -333,6 +353,10 @@ fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
                     let (input, ()) = pwm_pid(input)?;
                     Ok((input, Ok(Command::PwmPid { channel })))
                 },
+                |input| {
+                    let (input, swapped) = pwm_polarity_swapped(input)?;
+                    Ok((input, Ok(Command::PwmPolaritySwapped { channel, swapped })))
+                },
                 |input| {
                     let (input, config) = pwm_setup(input)?;
                     match config {

src/config.rs

@@ -20,6 +20,7 @@ pub struct ChannelConfig {
     pid_target: f32,
     pid_engaged: bool,
     i_set: ElectricCurrent,
+    polarity_swapped: bool,
     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_swapped: state.polarity_swapped,
             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.swap_polarity(channel, self.polarity_swapped);
     }
 }