Add command for flipping output polarity

Needed for IDC cable connections, since the IDC connector and front
panel connectors have flipped polarities.

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

@@ -157,7 +157,11 @@ 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);
+        let mut i_set = i_set.min(MAX_TEC_I).max(-MAX_TEC_I);
+        self.channel_state(channel).i_set = i_set;
+        if self.channel_state(channel).polarity_swapped {
+            i_set = -i_set;
+        }
         let vref_meas = match channel.into() {
             0 => self.channel0.vref_meas,
             1 => self.channel1.vref_meas,
@@ -168,7 +172,6 @@ impl Channels {
         let voltage = 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;
         i_set
     }
 
@@ -397,7 +400,12 @@ impl Channels {
 
     // 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

src/command_handler.rs

@@ -181,6 +181,15 @@ impl Handler {
         Ok(Handler::Handled)
     }
 
+    fn swap_polarity (socket: &mut TcpSocket, channels: &mut Channels, channel: usize, swapped: bool) -> Result<Handler, Error> {
+        channels.channel_state(channel).polarity_swapped = swapped;
+        let channel_state = channels.channel_state(channel);
+        let i_set = channel_state.i_set;
+        channels.set_i(channel, i_set);
+        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 +433,7 @@ 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 {