implement setting i_set centerpoint

README.md

@@ -57,6 +57,8 @@ The scope of this setting is per TCP session.
 | `pwm <0/1> max_v <ratio>`        | Set PWM duty cycle for **max_v** to *volt*          |
 | `pwm <0/1> <volts>`              | Disengage PID, set **i_set** DAC to *ampere*        |
 | `pwm <0/1> pid`                  | Set PWM to be controlled by PID                     |
+| `center <0/1> <volts>`           | Set the MAX1968 0A-centerpoint to *volts*           |
+| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to measure from VREF |
 | `pid`                            | Show PID configuration                              |
 | `pid <0/1> target <value>`       | Set the PID controller target                       |
 | `pid <0/1> kp <value>`           | Set proportional gain                               |

src/channel_state.rs

@@ -13,6 +13,7 @@ use crate::{
     ad7172,
     pid,
     steinhart_hart as sh,
+    command_parser::CenterPoint,
 };
 
 const R_INNER: f64 = 2.0 * 5100.0;
@@ -24,6 +25,8 @@ pub struct ChannelState {
     pub adc_time: Instant,
     /// VREF for the TEC (1.5V)
     pub vref: ElectricPotential,
+    /// i_set 0A center point
+    pub center: CenterPoint,
     pub dac_value: ElectricPotential,
     pub pid_engaged: bool,
     pub pid: pid::Controller,
@@ -36,8 +39,9 @@ impl ChannelState {
             adc_data: None,
             adc_calibration,
             adc_time: Instant::from_secs(0),
-            // can be initialized later with Channels.read_vref()
+            // updated later with Channels.read_vref()
-            vref: ElectricPotential::new::<volt>(3.3 / 2.0),
+            vref: ElectricPotential::new::<volt>(1.5),
+            center: CenterPoint::Vref,
             dac_value: ElectricPotential::new::<volt>(0.0),
             pid_engaged: false,
             pid: pid::Controller::new(pid::Parameters::default()),

src/channels.rs

@@ -13,7 +13,7 @@ use crate::{
     ad7172,
     channel::{Channel, Channel0, Channel1},
     channel_state::ChannelState,
-    command_parser::PwmPin,
+    command_parser::{CenterPoint, PwmPin},
     pins,
 };
 
@@ -99,11 +99,17 @@ impl Channels {
     }
 
     pub fn get_i(&mut self, channel: usize) -> (ElectricCurrent, ElectricCurrent) {
-        let vref = self.channel_state(channel).vref;
+        let state = self.channel_state(channel);
+        let center_point = match state.center {
+            CenterPoint::Vref =>
+                state.vref,
+            CenterPoint::Override(center_point) =>
+                ElectricPotential::new::<volt>(center_point),
+        };
         let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
         let (voltage, max) = self.get_dac(channel);
-        let i_tec = (voltage - vref) / (10.0 * r_sense);
+        let i_tec = (voltage - center_point) / (10.0 * r_sense);
-        let max = (max - vref) / (10.0 * r_sense);
+        let max = (max - center_point) / (10.0 * r_sense);
         (i_tec, max)
     }
 
@@ -127,12 +133,18 @@ impl Channels {
     }
 
     pub fn set_i(&mut self, channel: usize, i_tec: ElectricCurrent) -> (ElectricCurrent, ElectricCurrent) {
-        let vref = self.channel_state(channel).vref;
+        let state = self.channel_state(channel);
+        let center_point = match state.center {
+            CenterPoint::Vref =>
+                state.vref,
+            CenterPoint::Override(center_point) =>
+                ElectricPotential::new::<volt>(center_point),
+        };
         let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
-        let voltage = i_tec * 10.0 * r_sense + vref;
+        let voltage = i_tec * 10.0 * r_sense + center_point;
         let (voltage, max) = self.set_dac(channel, voltage);
-        let i_tec = (voltage - vref) / (10.0 * r_sense);
+        let i_tec = (voltage - center_point) / (10.0 * r_sense);
-        let max = (max - vref) / (10.0 * r_sense);
+        let max = (max - center_point) / (10.0 * r_sense);
         (i_tec, max)
     }
 

src/command_parser.rs

@@ -122,6 +122,12 @@ pub enum PwmPin {
     MaxV,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum CenterPoint {
+    Vref,
+    Override(f64),
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Command {
     Quit,
@@ -137,6 +143,10 @@ pub enum Command {
     PwmPid {
         channel: usize,
     },
+    CenterPoint {
+        channel: usize,
+        center: CenterPoint,
+    },
     /// PID parameter setting
     Pid {
         channel: usize,
@@ -290,6 +300,25 @@ fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     ))(input)
 }
 
+fn center_point(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+    let (input, _) = tag("center")(input)?;
+    let (input, _) = whitespace(input)?;
+    let (input, channel) = channel(input)?;
+    let (input, _) = whitespace(input)?;
+    let (input, center) = alt((
+        value(Ok(CenterPoint::Vref), tag("vref")),
+        |input| {
+            let (input, value) = float(input)?;
+            Ok((input, value.map(CenterPoint::Override)))
+        }
+    ))(input)?;
+    end(input)?;
+    Ok((input, center.map(|center| Command::CenterPoint {
+        channel,
+        center,
+    })))
+}
+
 /// `pid <0-1> <parameter> <value>`
 fn pid_parameter(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     let (input, channel) = channel(input)?;
@@ -378,6 +407,7 @@ fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     alt((value(Ok(Command::Quit), tag("quit")),
          map(report, Ok),
          pwm,
+         center_point,
          pid,
          steinhart_hart,
          postfilter,
@@ -529,4 +559,22 @@ mod test {
             rate: 21.0,
         }));
     }
+
+    #[test]
+    fn parse_center_point() {
+        let command = Command::parse(b"center 0 1.5");
+        assert_eq!(command, Ok(Command::CenterPoint {
+            channel: 0,
+            center: CenterPoint::Override(1.5),
+        }));
+    }
+
+    #[test]
+    fn parse_center_point_vref() {
+        let command = Command::parse(b"center 1 vref");
+        assert_eq!(command, Ok(Command::CenterPoint {
+            channel: 1,
+            center: CenterPoint::Vref,
+        }));
+    }
 }

src/main.rs

@@ -55,7 +55,7 @@ use server::Server;
 mod session;
 use session::{Session, SessionOutput};
 mod command_parser;
-use command_parser::{Command, ShowCommand, PwmPin};
+use command_parser::{CenterPoint, Command, ShowCommand, PwmPin};
 mod timer;
 mod pid;
 mod steinhart_hart;
@@ -221,18 +221,32 @@ fn main() -> ! {
                                 }
                                 Command::Show(ShowCommand::Pwm) => {
                                     for channel in 0..CHANNELS {
+                                        let i_set = channels.get_i(channel);
                                         let state = channels.channel_state(channel);
                                         let _ = writeln!(
                                             socket, "channel {}: PID={}",
                                             channel,
                                             if state.pid_engaged { "engaged" } else { "disengaged" }
                                         );
-                                        let i_set = channels.get_i(channel);
+                                        let _ = write!(
-                                        let _ = writeln!(
+                                            socket, "- i_set={:.3} / {:.3} ",
-                                            socket, "- i_set={:.3} / {:.3}",
                                             i_set.0.into_format_args(ampere, Abbreviation),
                                             i_set.1.into_format_args(ampere, Abbreviation),
                                         );
+                                        match state.center {
+                                            CenterPoint::Vref => {
+                                                let _ = writeln!(
+                                                    socket, "center=vref vref={:.3}",
+                                                    state.vref.into_format_args(volt, Abbreviation),
+                                                );
+                                            }
+                                            CenterPoint::Override(volts) => {
+                                                let _ = writeln!(
+                                                    socket, "center={:.3} V",
+                                                    volts,
+                                                );
+                                            }
+                                        }
                                         let max_v = channels.get_max_v(channel);
                                         let _ = writeln!(
                                             socket, "- max_v={:.3} / {:.3}",
@@ -321,7 +335,7 @@ fn main() -> ! {
                                             let voltage = ElectricPotential::new::<volt>(value);
                                             let (voltage, max) = channels.set_max_v(channel, voltage);
                                             let _ = writeln!(
-                                                socket, "channel {:.3}: max_v set to {:.3} / {:.3}",
+                                                socket, "channel {}: max_v set to {:.3} / {:.3}",
                                                 channel,
                                                 voltage.into_format_args(volt, Abbreviation),
                                                 max.into_format_args(volt, Abbreviation),
@@ -331,7 +345,7 @@ fn main() -> ! {
                                             let current = ElectricCurrent::new::<ampere>(value);
                                             let (current, max) = channels.set_max_i_pos(channel, current);
                                             let _ = writeln!(
-                                                socket, "channel {:.3}: max_i_pos set to {:.3} / {:.3}",
+                                                socket, "channel {}: max_i_pos set to {:.3} / {:.3}",
                                                 channel,
                                                 current.into_format_args(ampere, Abbreviation),
                                                 max.into_format_args(ampere, Abbreviation),
@@ -341,7 +355,7 @@ fn main() -> ! {
                                             let current = ElectricCurrent::new::<ampere>(value);
                                             let (current, max) = channels.set_max_i_neg(channel, current);
                                             let _ = writeln!(
-                                                socket, "channel {:.3}: max_i_neg set to {:.3} / {:.3}",
+                                                socket, "channel {}: max_i_neg set to {:.3} / {:.3}",
                                                 channel,
                                                 current.into_format_args(ampere, Abbreviation),
                                                 max.into_format_args(ampere, Abbreviation),
@@ -349,6 +363,23 @@ fn main() -> ! {
                                         }
                                     }
                                 }
+                                Command::CenterPoint { channel, center } => {
+                                    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_tec);
+                                        let _ = writeln!(
+                                            socket, "channel {}: center point updated, output readjusted for {:.3}",
+                                            channel, i_tec.into_format_args(ampere, Abbreviation),
+                                        );
+                                    } else {
+                                        let _ = writeln!(
+                                            socket, "channel {}: center point updated",
+                                            channel,
+                                        );
+                                    }
+                                }
                                 Command::Pid { channel, parameter, value } => {
                                     let pid = &mut channels.channel_state(channel).pid;
                                     use command_parser::PidParameter::*;