implement support for fan PWM

Co-authored-by: Egor Savkin <es@m-labs.hk>
Co-committed-by: Egor Savkin <es@m-labs.hk>

README.md

@@ -94,36 +94,42 @@ The scope of this setting is per TCP session.
 Send commands as simple text string terminated by `\n`. Responses are
 formatted as line-delimited JSON.
 
-| Syntax                           | Function                                                             |
+| Syntax                           | Function                                                                      |
-| ---                              | ---                                                                  |
+|----------------------------------|-------------------------------------------------------------------------------|
-| `report`                         | Show current input                                                   |
+| `report`                         | Show current input                                                            |
-| `report mode`                    | Show current report mode                                             |
+| `report mode`                    | Show current report mode                                                      |
-| `report mode <off/on>`           | Set report mode                                                      |
+| `report mode <off/on>`           | Set report mode                                                               |
-| `pwm`                            | Show current PWM settings                                            |
+| `pwm`                            | Show current PWM settings                                                     |
-| `pwm <0/1> max_i_pos <amp>`      | Set maximum positive output current                                  |
+| `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_i_neg <amp>`      | Set maximum negative output current                                           |
-| `pwm <0/1> max_v <volt>`         | Set maximum output voltage                                           |
+| `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> i_set <amp>`          | Disengage PID, set fixed output current                                       |
-| `pwm <0/1> pid`                  | Let output current to be controlled by the PID                       |
+| `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> <volt>`            | Set the MAX1968 0A-centerpoint to the specified fixed voltage                 |
-| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to measure from VREF                  |
+| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to measure from VREF                           |
-| `pid`                            | Show PID configuration                                               |
+| `pid`                            | Show PID configuration                                                        |
-| `pid <0/1> target <deg_celsius>` | Set the PID controller target temperature                            |
+| `pid <0/1> target <deg_celsius>` | Set the PID controller target temperature                                     |
-| `pid <0/1> kp <value>`           | Set proportional gain                                                |
+| `pid <0/1> kp <value>`           | Set proportional gain                                                         |
-| `pid <0/1> ki <value>`           | Set integral gain                                                    |
+| `pid <0/1> ki <value>`           | Set integral gain                                                             |
-| `pid <0/1> kd <value>`           | Set differential gain                                                |
+| `pid <0/1> kd <value>`           | Set differential gain                                                         |
-| `pid <0/1> output_min <amp>`     | Set mininum output                                                   |
+| `pid <0/1> output_min <amp>`     | Set mininum output                                                            |
-| `pid <0/1> output_max <amp>`     | Set maximum output                                                   |
+| `pid <0/1> output_max <amp>`     | Set maximum output                                                            |
-| `s-h`                            | Show Steinhart-Hart equation parameters                              |
+| `s-h`                            | Show Steinhart-Hart equation parameters                                       |
-| `s-h <0/1> <t0/b/r0> <value>`    | Set Steinhart-Hart parameter for a channel                           |
+| `s-h <0/1> <t0/b/r0> <value>`    | Set Steinhart-Hart parameter for a channel                                    |
-| `postfilter`                     | Show postfilter settings                                             |
+| `postfilter`                     | Show postfilter settings                                                      |
-| `postfilter <0/1> off`           | Disable postfilter                                                   |
+| `postfilter <0/1> off`           | Disable postfilter                                                            |
-| `postfilter <0/1> rate <rate>`   | Set postfilter output data rate                                      |
+| `postfilter <0/1> rate <rate>`   | Set postfilter output data rate                                               |
-| `load [0/1]`                     | Restore configuration for channel all/0/1 from flash                 |
+| `load [0/1]`                     | Restore configuration for channel all/0/1 from flash                          |
-| `save [0/1]`                     | Save configuration for channel all/0/1 to flash                      |
+| `save [0/1]`                     | Save configuration for channel all/0/1 to flash                               |
-| `reset`                          | Reset the device                                                     |
+| `reset`                          | Reset the device                                                              |
-| `dfu`                            | Reset device and enters USB device firmware update (DFU) mode        |
+| `dfu`                            | Reset device and enters USB device firmware update (DFU) mode                 |
-| `ipv4 <X.X.X.X/L> [Y.Y.Y.Y]`     | Configure IPv4 address, netmask length, and optional default gateway |
+| `ipv4 <X.X.X.X/L> [Y.Y.Y.Y]`     | Configure IPv4 address, netmask length, and optional default gateway          |
+| `fan`                            | Show current fan settings and sensors' measurements                           |
+| `fan <value>`                    | Set fan power with values from 1 to 100                                       |
+| `fan auto`                       | Enable automatic fan speed control                                            |
+| `fcurve <a> <b> <c>`             | Set fan controller curve coefficients (see *Fan control* section)             |
+| `fcurve default`                 | Set fan controller curve coefficients to defaults (see *Fan control* section) |
+| `hwrev`                          | Show hardware revision, and settings related to it                            |
 
 
 ## USB
@@ -269,3 +275,15 @@ with the following keys.
 ## 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:
+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.
+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`.

src/channels.rs

@@ -1,4 +1,5 @@
-use heapless::{consts::{U2, U1024}, Vec};
+use core::cmp::max_by;
+use heapless::{consts::U2, Vec};
 use serde::{Serialize, Serializer};
 use smoltcp::time::Instant;
 use stm32f4xx_hal::hal;
@@ -16,6 +17,7 @@ use crate::{
     channel::{Channel, Channel0, Channel1},
     channel_state::ChannelState,
     command_parser::{CenterPoint, PwmPin},
+    command_handler::JsonBuffer,
     pins,
     steinhart_hart,
 };
@@ -518,9 +520,13 @@ impl Channels {
         }
         serde_json_core::to_vec(&summaries)
     }
-}
 
-type JsonBuffer = Vec<u8, U1024>;
+    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>(),
+               |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal))
+    }
+}
 
 #[derive(Serialize)]
 pub struct Report {

src/command_handler.rs

@@ -1,6 +1,7 @@
 use smoltcp::socket::TcpSocket;
 use log::{error, warn};
 use core::fmt::Write;
+use heapless::{consts::U1024, Vec};
 use super::{
     net,
     command_parser::{
@@ -22,7 +23,9 @@ use super::{
     config::ChannelConfig,
     dfu,
     flash_store::FlashStore,
-    session::Session
+    session::Session,
+    FanCtrl,
+    hw_rev::HWRev,
 };
 
 use uom::{
@@ -55,6 +58,8 @@ pub enum Error {
     FlashError
 }
 
+pub type JsonBuffer = Vec<u8, U1024>;
+
 fn send_line(socket: &mut TcpSocket, data: &[u8]) -> bool {
     let send_free = socket.send_capacity() - socket.send_queue();
     if data.len() > send_free + 1 {
@@ -341,7 +346,76 @@ impl Handler {
         Ok(Handler::Reset)
     }
 
-    pub fn handle_command (command: Command, socket: &mut TcpSocket, channels: &mut Channels, session: &Session, leds: &mut Leds, store: &mut FlashStore, ipv4_config: &mut Ipv4Config) -> Result<Self, Error> {
+    fn set_fan(socket: &mut TcpSocket, fan_pwm: u32, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
+        if !fan_ctrl.fan_available() {
+            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have fan!\" }");
+            return Ok(Handler::Handled);
+        }
+        fan_ctrl.set_auto_mode(false);
+        fan_ctrl.set_pwm(fan_pwm);
+        if fan_ctrl.fan_pwm_recommended() {
+            send_line(socket, b"{}");
+        } else {
+            send_line(socket, b"{ \"warning\": \"this fan doesn't have full PWM support. Use it at your own risk!\" }");
+        }
+        Ok(Handler::Handled)
+    }
+
+    fn show_fan(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
+        match fan_ctrl.summary() {
+            Ok(buf) => {
+                send_line(socket, &buf);
+                Ok(Handler::Handled)
+            }
+            Err(e) => {
+                error!("unable to serialize fan summary: {:?}", e);
+                let _ = writeln!(socket, "{{\"error\":\"{:?}\"}}", e);
+                Err(Error::ReportError)
+            }
+        }
+    }
+
+    fn fan_auto(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
+        if !fan_ctrl.fan_available() {
+            send_line(socket, b"{ \"warning\": \"this thermostat doesn't have fan!\" }");
+            return Ok(Handler::Handled);
+        }
+        fan_ctrl.set_auto_mode(true);
+        if fan_ctrl.fan_pwm_recommended() {
+            send_line(socket, b"{}");
+        } else {
+            send_line(socket, b"{ \"warning\": \"this fan doesn't have full PWM support. Use it at your own risk!\" }");
+        }
+        Ok(Handler::Handled)
+    }
+
+    fn fan_curve(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl, k_a: f32, k_b: f32, k_c: f32) -> Result<Handler, Error> {
+        fan_ctrl.set_curve(k_a, k_b, k_c);
+        send_line(socket, b"{}");
+        Ok(Handler::Handled)
+    }
+
+    fn fan_defaults(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
+        fan_ctrl.restore_defaults();
+        send_line(socket, b"{}");
+        Ok(Handler::Handled)
+    }
+
+    fn show_hwrev(socket: &mut TcpSocket, hwrev: HWRev) -> Result<Handler, Error> {
+        match hwrev.summary() {
+            Ok(buf) => {
+                send_line(socket, &buf);
+                Ok(Handler::Handled)
+            }
+            Err(e) => {
+                error!("unable to serialize HWRev summary: {:?}", e);
+                let _ = writeln!(socket, "{{\"error\":\"{:?}\"}}", e);
+                Err(Error::ReportError)
+            }
+        }
+    }
+
+    pub fn handle_command(command: Command, socket: &mut TcpSocket, channels: &mut Channels, session: &Session, leds: &mut Leds, store: &mut FlashStore, ipv4_config: &mut Ipv4Config, fan_ctrl: &mut FanCtrl, hwrev: HWRev) -> Result<Self, Error> {
         match command {
             Command::Quit => Ok(Handler::CloseSocket),
             Command::Reporting(_reporting) => Handler::reporting(socket),            
@@ -363,7 +437,13 @@ impl Handler {
             Command::Save { channel } => Handler::save_channel(socket, channels, channel, store),
             Command::Ipv4(config) => Handler::set_ipv4(socket, store, config),
             Command::Reset => Handler::reset(channels),
-            Command::Dfu => Handler::dfu(channels)
+            Command::Dfu => Handler::dfu(channels),
+            Command::FanSet {fan_pwm} => Handler::set_fan(socket, fan_pwm, fan_ctrl),
+            Command::ShowFan => Handler::show_fan(socket, fan_ctrl),
+            Command::FanAuto => Handler::fan_auto(socket, fan_ctrl),
+            Command::FanCurve { k_a, k_b, k_c } => Handler::fan_curve(socket, fan_ctrl, k_a, k_b, k_c),
+            Command::FanCurveDefaults => Handler::fan_defaults(socket, fan_ctrl),
+            Command::ShowHWRev => Handler::show_hwrev(socket, hwrev),
         }
     }
 }

src/command_parser.rs

@@ -10,6 +10,7 @@ use nom::{
     sequence::preceded,
     multi::{fold_many0, fold_many1},
     error::ErrorKind,
+    Needed,
 };
 use num_traits::{Num, ParseFloatError};
 use serde::{Serialize, Deserialize};
@@ -178,6 +179,18 @@ pub enum Command {
         rate: Option<f32>,
     },
     Dfu,
+    FanSet {
+        fan_pwm: u32
+    },
+    FanAuto,
+    ShowFan,
+    FanCurve {
+        k_a: f32,
+        k_b: f32,
+        k_c: f32,
+    },
+    FanCurveDefaults,
+    ShowHWRev,
 }
 
 fn end(input: &[u8]) -> IResult<&[u8], ()> {
@@ -520,6 +533,57 @@ fn ipv4(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     ))(input)
 }
 
+fn fan(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+    let (input, _) = tag("fan")(input)?;
+    alt((
+        |input| {
+            let (input, _) = whitespace(input)?;
+
+            let (input, result) = alt((
+                |input| {
+                    let (input, _) = tag("auto")(input)?;
+                    Ok((input, Ok(Command::FanAuto)))
+                },
+                |input| {
+                    let (input, value) = unsigned(input)?;
+                    Ok((input, Ok(Command::FanSet { fan_pwm: value.unwrap_or(0)})))
+                },
+            ))(input)?;
+            Ok((input, result))
+        },
+        value(Ok(Command::ShowFan), end)
+    ))(input)
+}
+
+fn fan_curve(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+    let (input, _) = tag("fcurve")(input)?;
+    alt((
+        |input| {
+            let (input, _) = whitespace(input)?;
+            let (input, result) = alt((
+                |input| {
+                    let (input, _) = tag("default")(input)?;
+                    Ok((input, Ok(Command::FanCurveDefaults)))
+                },
+                |input| {
+                    let (input, k_a) = float(input)?;
+                    let (input, _) = whitespace(input)?;
+                    let (input, k_b) = float(input)?;
+                    let (input, _) = whitespace(input)?;
+                    let (input, k_c) = float(input)?;
+                    if k_a.is_ok() && k_b.is_ok() && k_c.is_ok() {
+                        Ok((input, Ok(Command::FanCurve { k_a: k_a.unwrap() as f32, k_b: k_b.unwrap() as f32, k_c: k_c.unwrap() as f32 })))
+                    } else {
+                        Err(nom::Err::Incomplete(Needed::Size(3)))
+                    }
+                },
+            ))(input)?;
+            Ok((input, result))
+        },
+        value(Err(Error::Incomplete), end)
+    ))(input)
+}
+
 fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     alt((value(Ok(Command::Quit), tag("quit")),
          load,
@@ -533,6 +597,9 @@ fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
          steinhart_hart,
          postfilter,
          value(Ok(Command::Dfu), tag("dfu")),
+         fan,
+         fan_curve,
+         value(Ok(Command::ShowHWRev), tag("hwrev")),
     ))(input)
 }
 
@@ -754,4 +821,44 @@ mod test {
             center: CenterPoint::Vref,
         }));
     }
+
+    #[test]
+    fn parse_fan_show() {
+        let command = Command::parse(b"fan");
+        assert_eq!(command, Ok(Command::ShowFan));
+    }
+
+    #[test]
+    fn parse_fan_set() {
+        let command = Command::parse(b"fan 42");
+        assert_eq!(command, Ok(Command::FanSet {fan_pwm: 42}));
+    }
+
+    #[test]
+    fn parse_fan_auto() {
+        let command = Command::parse(b"fan auto");
+        assert_eq!(command, Ok(Command::FanAuto));
+    }
+
+    #[test]
+    fn parse_fcurve_set() {
+        let command = Command::parse(b"fcurve 1.2 3.4 5.6");
+        assert_eq!(command, Ok(Command::FanCurve {
+            k_a: 1.2,
+            k_b: 3.4,
+            k_c: 5.6
+        }));
+    }
+
+    #[test]
+    fn parse_fcurve_default() {
+        let command = Command::parse(b"fcurve default");
+        assert_eq!(command, Ok(Command::FanCurveDefaults));
+    }
+
+    #[test]
+    fn parse_hwrev() {
+        let command = Command::parse(b"hwrev");
+        assert_eq!(command, Ok(Command::ShowHWRev));
+    }
 }

src/fan_ctrl.rs

@@ -0,0 +1,151 @@
+use num_traits::Float;
+use serde::Serialize;
+use stm32f4xx_hal::{
+    pwm::{self, PwmChannels},
+    pac::TIM8,
+};
+
+use crate::{
+    hw_rev::HWSettings,
+    command_handler::JsonBuffer,
+};
+
+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;
+
+
+pub struct FanCtrl {
+    fan: Option<FanPin>,
+    fan_auto: bool,
+    pwm_enabled: bool,
+    k_a: f32,
+    k_b: f32,
+    k_c: f32,
+    abs_max_tec_i: f32,
+    hw_settings: HWSettings,
+}
+
+impl FanCtrl {
+    pub fn new(fan: Option<FanPin>, hw_settings: HWSettings) -> Self {
+        let mut fan_ctrl = FanCtrl {
+            fan,
+            // do not enable auto mode by default,
+            // but allow to turn it at the user's own risk
+            fan_auto: hw_settings.fan_pwm_recommended,
+            pwm_enabled: false,
+            k_a: hw_settings.fan_k_a,
+            k_b: hw_settings.fan_k_b,
+            k_c: hw_settings.fan_k_c,
+            abs_max_tec_i: 0f32,
+            hw_settings,
+        };
+        if fan_ctrl.fan_auto {
+            fan_ctrl.enable_pwm();
+        }
+        fan_ctrl
+    }
+
+    pub fn cycle(&mut self, abs_max_tec_i: f32) {
+        self.abs_max_tec_i = abs_max_tec_i;
+        if self.fan_auto && self.hw_settings.fan_available {
+            let scaled_current = self.abs_max_tec_i / MAX_TEC_I;
+            // 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);
+        }
+    }
+
+    pub fn summary(&mut self) -> Result<JsonBuffer, serde_json_core::ser::Error> {
+        if self.hw_settings.fan_available {
+            let summary = FanSummary {
+                fan_pwm: self.get_pwm(),
+                abs_max_tec_i: self.abs_max_tec_i,
+                auto_mode: self.fan_auto,
+                k_a: self.k_a,
+                k_b: self.k_b,
+                k_c: self.k_c,
+            };
+            serde_json_core::to_vec(&summary)
+        } else {
+            let summary: Option<()> = None;
+            serde_json_core::to_vec(&summary)
+        }
+    }
+
+    pub fn set_auto_mode(&mut self, fan_auto: bool) {
+        self.fan_auto = fan_auto;
+    }
+
+    pub fn set_curve(&mut self, k_a: f32, k_b: f32, k_c: f32) {
+        self.k_a = k_a;
+        self.k_b = k_b;
+        self.k_c = k_c;
+    }
+
+    pub fn restore_defaults(&mut self) {
+        self.set_curve(self.hw_settings.fan_k_a,
+                       self.hw_settings.fan_k_b,
+                       self.hw_settings.fan_k_c);
+    }
+
+    pub fn set_pwm(&mut self, fan_pwm: u32) -> f32 {
+        if self.fan.is_none() || (!self.pwm_enabled && !self.enable_pwm())  {
+            return 0f32;
+        }
+        let fan = self.fan.as_mut().unwrap();
+        let fan_pwm = fan_pwm.min(MAX_USER_FAN_PWM as u32).max(MIN_USER_FAN_PWM as u32);
+        let duty = scale_number(fan_pwm as f32, self.hw_settings.min_fan_pwm, self.hw_settings.max_fan_pwm, MIN_USER_FAN_PWM, MAX_USER_FAN_PWM);
+        let max = fan.get_max_duty();
+        let value = ((duty * (max as f32)) as u16).min(max);
+        fan.set_duty(value);
+        value as f32 / (max as f32)
+    }
+
+    pub fn fan_pwm_recommended(&self) -> bool {
+        self.hw_settings.fan_pwm_recommended
+    }
+
+    pub fn fan_available(&self) -> bool {
+        self.hw_settings.fan_available
+    }
+
+    fn get_pwm(&self) -> u32 {
+        if let Some(fan) = &self.fan {
+            let duty = fan.get_duty();
+            let max = fan.get_max_duty();
+            scale_number(duty as f32 / (max as f32), MIN_USER_FAN_PWM, MAX_USER_FAN_PWM, self.hw_settings.min_fan_pwm, self.hw_settings.max_fan_pwm).round() as u32
+        } else { 0 }
+    }
+
+    fn enable_pwm(&mut self) -> bool {
+        if self.fan.is_some() && self.hw_settings.fan_available {
+            let fan = self.fan.as_mut().unwrap();
+            fan.set_duty(0);
+            fan.enable();
+            self.pwm_enabled = true;
+            true
+        } else {
+            false
+        }
+    }
+}
+
+
+fn scale_number(unscaled: f32, to_min: f32, to_max: f32, from_min: f32, from_max: f32) -> f32 {
+    (to_max - to_min) * (unscaled - from_min) / (from_max - from_min) + to_min
+}
+
+#[derive(Serialize)]
+pub struct FanSummary {
+    fan_pwm: u32,
+    abs_max_tec_i: f32,
+    auto_mode: bool,
+    k_a: f32,
+    k_b: f32,
+    k_c: f32,
+}

src/hw_rev.rs

@@ -0,0 +1,82 @@
+use serde::Serialize;
+
+use crate::{
+    pins::HWRevPins,
+    command_handler::JsonBuffer,
+};
+
+#[derive(Serialize, Copy, Clone)]
+pub struct HWRev {
+    pub major: u8,
+    pub minor: u8,
+}
+
+#[derive(Serialize, Clone)]
+pub struct HWSettings {
+    pub fan_k_a: f32,
+    pub fan_k_b: f32,
+    pub fan_k_c: f32,
+    pub min_fan_pwm: f32,
+    pub max_fan_pwm: f32,
+    pub fan_pwm_freq_hz: u32,
+    pub fan_available: bool,
+    pub fan_pwm_recommended: bool,
+}
+
+#[derive(Serialize, Clone)]
+struct HWSummary<'a> {
+    rev: &'a HWRev,
+    settings: &'a HWSettings,
+}
+
+impl HWRev {
+    pub fn detect_hw_rev(hwrev_pins: &HWRevPins) -> Self {
+        let (h0, h1, h2, h3) = (hwrev_pins.hwrev0.is_high(), hwrev_pins.hwrev1.is_high(),
+                                hwrev_pins.hwrev2.is_high(), hwrev_pins.hwrev3.is_high());
+        match (h0, h1, h2, h3) {
+            (true, true, true, false) => HWRev { major: 1, minor: 0 },
+            (true, false, false, false) => HWRev { major: 2, minor: 0 },
+            (false, true, false, false) => HWRev { major: 2, minor: 2 },
+            (_, _, _, _) => HWRev { major: 0, minor: 0 }
+        }
+    }
+
+    pub fn settings(&self) -> HWSettings {
+        match (self.major, self.minor) {
+            (2, 2) => HWSettings {
+                fan_k_a: 1.0,
+                fan_k_b: 0.0,
+                fan_k_c: 0.0,
+                // below this value motor's autostart feature may fail,
+                // according to internal experiments
+                min_fan_pwm: 0.04,
+                max_fan_pwm: 1.0,
+                // According to `SUNON DC Brushless Fan & Blower(255-E)` catalogue p.36-37
+                // model MF35101V1-1000U-G99 doesn't have a PWM wire, but we'll follow their others models'
+                // recommended frequency, as it is said by the Thermostat's schematics that we can
+                // use PWM, but not stated at which frequency
+                fan_pwm_freq_hz: 25_000,
+                fan_available: true,
+                // see https://github.com/sinara-hw/Thermostat/issues/115 and
+                // https://git.m-labs.hk/M-Labs/thermostat/issues/69#issuecomment-6464 for explanation
+                fan_pwm_recommended: false,
+            },
+            (_, _) => HWSettings {
+                fan_k_a: 0.0,
+                fan_k_b: 0.0,
+                fan_k_c: 0.0,
+                min_fan_pwm: 0.0,
+                max_fan_pwm: 0.0,
+                fan_pwm_freq_hz: 0,
+                fan_available: false,
+                fan_pwm_recommended: false,
+            }
+        }
+    }
+
+    pub fn summary(&self) -> Result<JsonBuffer, serde_json_core::ser::Error> {
+        let settings = self.settings();
+        let summary = HWSummary { rev: self, settings: &settings };
+        serde_json_core::to_vec(&summary)
+    }
+}

src/main.rs

@@ -10,7 +10,6 @@ use panic_abort as _;
 use panic_semihosting as _;
 
 use log::{error, info, warn};
-
 use cortex_m::asm::wfi;
 use cortex_m_rt::entry;
 use stm32f4xx_hal::{
@@ -54,6 +53,9 @@ mod flash_store;
 mod dfu;
 mod command_handler;
 use command_handler::Handler;
+mod fan_ctrl;
+use fan_ctrl::FanCtrl;
+mod hw_rev;
 
 const HSE: MegaHertz = MegaHertz(8);
 #[cfg(not(feature = "semihosting"))]
@@ -118,8 +120,8 @@ fn main() -> ! {
 
     timer::setup(cp.SYST, clocks);
 
-    let (pins, mut leds, mut eeprom, eth_pins, usb) = Pins::setup(
+    let (pins, mut leds, mut eeprom, eth_pins, usb, fan, hwrev, hw_settings) = Pins::setup(
-        clocks, dp.TIM1, dp.TIM3,
+        clocks, dp.TIM1, dp.TIM3, dp.TIM8,
         dp.GPIOA, dp.GPIOB, dp.GPIOC, dp.GPIOD, dp.GPIOE, dp.GPIOF, dp.GPIOG,
         dp.I2C1,
         dp.SPI2, dp.SPI4, dp.SPI5,
@@ -137,7 +139,6 @@ fn main() -> ! {
 
     let mut store = flash_store::store(dp.FLASH);
 
-
     let mut channels = Channels::new(pins);
     for c in 0..CHANNELS {
         match store.read_value::<ChannelConfig>(CHANNEL_CONFIG_KEY[c]) {
@@ -150,6 +151,8 @@ fn main() -> ! {
         }
     }
 
+    let mut fan_ctrl = FanCtrl::new(fan, hw_settings);
+
     // default net config:
     let mut ipv4_config = Ipv4Config {
         address: [192, 168, 1, 26],
@@ -183,6 +186,8 @@ fn main() -> ! {
                     server.for_each(|_, session| session.set_report_pending(channel.into()));
                 }
 
+                fan_ctrl.cycle(channels.current_abs_max_tec_i() as f32);
+
                 let instant = Instant::from_millis(i64::from(timer::now()));
                 cortex_m::interrupt::free(net::clear_pending);
                 server.poll(instant)
@@ -206,7 +211,7 @@ fn main() -> ! {
                                 // Do nothing and feed more data to the line reader in the next loop cycle.
                                 Ok(SessionInput::Nothing) => {}
                                 Ok(SessionInput::Command(command)) => {
-                                    match Handler::handle_command(command, &mut socket, &mut channels, session, &mut leds, &mut store, &mut ipv4_config) {
+                                    match Handler::handle_command(command, &mut socket, &mut channels, session, &mut leds, &mut store, &mut ipv4_config, &mut fan_ctrl, hwrev) {
                                         Ok(Handler::NewIPV4(ip)) => new_ipv4_config = Some(ip),                                
                                         Ok(Handler::Handled) => {},
                                         Ok(Handler::CloseSocket) => socket.close(),

src/pins.rs

@@ -23,7 +23,7 @@ use stm32f4xx_hal::{
         I2C1,
         OTG_FS_GLOBAL, OTG_FS_DEVICE, OTG_FS_PWRCLK,
         SPI2, SPI4, SPI5,
-        TIM1, TIM3,
+        TIM1, TIM3, TIM8
     },
     timer::Timer,
     time::U32Ext,
@@ -33,6 +33,8 @@ use stm32_eth::EthPins;
 use crate::{
     channel::{Channel0, Channel1},
     leds::Leds,
+    fan_ctrl::FanPin,
+    hw_rev::{HWRev, HWSettings},
 };
 
 pub type Eeprom = Eeprom24x<
@@ -101,6 +103,13 @@ pub struct ChannelPinSet<C: ChannelPins> {
     pub tec_u_meas_pin: C::TecUMeasPin,
 }
 
+pub struct HWRevPins {
+    pub hwrev0: stm32f4xx_hal::gpio::gpiod::PD0<Input<Floating>>,
+    pub hwrev1: stm32f4xx_hal::gpio::gpiod::PD1<Input<Floating>>,
+    pub hwrev2: stm32f4xx_hal::gpio::gpiod::PD2<Input<Floating>>,
+    pub hwrev3: stm32f4xx_hal::gpio::gpiod::PD3<Input<Floating>>,
+}
+
 pub struct Pins {
     pub adc_spi: AdcSpi,
     pub adc_nss: AdcNss,
@@ -114,13 +123,13 @@ impl Pins {
     /// Setup GPIO pins and configure MCU peripherals
     pub fn setup(
         clocks: Clocks,
-        tim1: TIM1, tim3: TIM3,
+        tim1: TIM1, tim3: TIM3, tim8: TIM8,
         gpioa: GPIOA, gpiob: GPIOB, gpioc: GPIOC, gpiod: GPIOD, gpioe: GPIOE, gpiof: GPIOF, gpiog: GPIOG,
         i2c1: I2C1,
         spi2: SPI2, spi4: SPI4, spi5: SPI5,
         adc1: ADC1,
         otg_fs_global: OTG_FS_GLOBAL, otg_fs_device: OTG_FS_DEVICE, otg_fs_pwrclk: OTG_FS_PWRCLK,
-    ) -> (Self, Leds, Eeprom, EthernetPins, USB) {
+    ) -> (Self, Leds, Eeprom, EthernetPins, USB, Option<FanPin>, HWRev, HWSettings) {
         let gpioa = gpioa.split();
         let gpiob = gpiob.split();
         let gpioc = gpioc.split();
@@ -189,6 +198,10 @@ 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();
@@ -215,7 +228,11 @@ impl Pins {
             hclk: clocks.hclk(),
         };
 
-        (pins, leds, eeprom, eth_pins, usb)
+        let fan = if hw_settings.fan_available {
+             Some(Timer::new(tim8, &clocks).pwm(gpioc.pc9.into_alternate(), hw_settings.fan_pwm_freq_hz.hz()))
+        } else { None };
+
+        (pins, leds, eeprom, eth_pins, usb, fan, hwrev, hw_settings)
     }
 
     /// Configure the GPIO pins for SPI operation, and initialize SPI