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                                                           |
@@ -126,6 +126,8 @@ formatted as line-delimited JSON.
 | `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 0 to 100, where 0 is auto mode             |
+| `fcurve <a> <b> <c>`             | Set fan controller coefficients (see *Fan control* section)               |
+| `fan-restore`                    | Set fan controller coefficients to defaults (see *Fan control* section)   |
 
 
 ## USB
@@ -274,10 +276,14 @@ The thermostat implements a PID control loop for each of the TEC channels, more
 
 ## Fan control
 
-Fan control is available for the thermostat revisions with integrated fan system. For this purpose two commands are available:
+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`, `tacho`, `abs_max_tec_i`, `auto_mode`. Please note that `tacho` shows *approximate* value, which
 linearly correlates with the actual fan speed.
 2. `fan <value>` - set the fan power with the value from `0` to `100`. Since there is no hardware way to disable the fan,
 `0` value is used for enabling automatic fan control mode, which correlates with the square of the TEC's current. 
 Values from `1` to `100` are used for setting the power from minimum to maximum respectively.
 Please note that power doesn't correlate with the actual speed linearly.
+3. `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.
+4. `fan-restore` - restore fan settings to defaults: `auto = true, a = 1.0, b = 0.0, c = 0.0`.

src/channels.rs

@@ -19,22 +19,13 @@ use crate::{
     command_parser::{CenterPoint, PwmPin},
     pins,
     steinhart_hart,
+    fan_ctrl::HWRev,
 };
-use crate::pins::HWRevPins;
 
 pub const CHANNELS: usize = 2;
 pub const R_SENSE: f64 = 0.05;
 // DAC chip outputs 0-5v, which is then passed through a resistor dividor to provide 0-3v range
 const DAC_OUT_V_MAX: f64 = 3.0;
-const MAX_TEC_I: f64 = 3.0; // as stated in the schemes
-const MAX_FAN_PWM: f64 = 100.0;
-const MIN_FAN_PWM: f64 = 1.0;
-
-#[derive(Serialize, Copy, Clone)]
-pub struct HWRev {
-    pub major: u8,
-    pub minor: u8
-}
 
 // TODO: -pub
 pub struct Channels {
@@ -44,8 +35,7 @@ pub struct Channels {
     /// stm32f4 integrated adc
     pins_adc: pins::PinsAdc,
     pub pwm: pins::PwmPins,
-    hw_rev: HWRev,
+    pub hwrev: HWRev,
-    fan_auto: bool
 }
 
 impl Channels {
@@ -68,7 +58,7 @@ impl Channels {
         let pins_adc = pins.pins_adc;
         let pwm = pins.pwm;
         let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm,
-            hw_rev: Self::detect_hw_rev(&pins.hwrev), fan_auto: true };
+            hwrev: HWRev::detect_hw_rev(&pins.hwrev)};
         for channel in 0..CHANNELS {
             channels.channel_state(channel).vref = channels.read_vref(channel);
             channels.calibrate_dac_value(channel);
@@ -77,21 +67,6 @@ impl Channels {
         channels
     }
 
-    fn detect_hw_rev(hwrev_pins: &HWRevPins) -> HWRev {
-        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 fan_available(&self) -> bool {
-        self.hw_rev.major == 2 && self.hw_rev.minor == 2
-    }
-
     pub fn channel_state<I: Into<usize>>(&mut self, channel: I) -> &mut ChannelState {
         match channel.into() {
             0 => &mut self.channel0.state,
@@ -365,8 +340,6 @@ impl Channels {
         match (channel, pin) {
             (_, PwmPin::ISet) =>
                 panic!("i_set is no pwm pin"),
-            (_, PwmPin::Fan) =>
-                get(&self.pwm.fan),
             (0, PwmPin::MaxIPos) =>
                 get(&self.pwm.max_i_pos0),
             (0, PwmPin::MaxINeg) =>
@@ -422,8 +395,6 @@ impl Channels {
         match (channel, pin) {
             (_, PwmPin::ISet) =>
                 panic!("i_set is no pwm pin"),
-            (_, PwmPin::Fan) =>
-                set(&mut self.pwm.fan, duty),
             (0, PwmPin::MaxIPos) =>
                 set(&mut self.pwm.max_i_pos0, duty),
             (0, PwmPin::MaxINeg) =>
@@ -462,19 +433,6 @@ impl Channels {
         (duty * max, max)
     }
 
-    pub fn set_fan_pwm(&mut self, fan_pwm: u32) -> f64 {
-        let duty = fan_pwm as f64 / MAX_FAN_PWM;
-        self.set_pwm(0, PwmPin::Fan, duty)
-    }
-
-    pub fn get_fan_pwm(&mut self) -> u32 {
-        (self.get_pwm(0, PwmPin::Fan) * MAX_FAN_PWM) as u32
-    }
-
-    pub fn set_fan_auto_mode(&mut self, fan_auto: bool) {
-        self.fan_auto = fan_auto;
-    }
-
     fn report(&mut self, channel: usize) -> Report {
         let vref = self.channel_state(channel).vref;
         let i_set = self.get_i(channel);
@@ -500,7 +458,7 @@ impl Channels {
             tec_i,
             tec_u_meas: self.get_tec_v(channel),
             pid_output,
-            hwrev: self.hw_rev
+            hwrev: self.hwrev
         }
     }
 
@@ -566,39 +524,14 @@ impl Channels {
         serde_json_core::to_vec(&summaries)
     }
 
-    fn current_abs_max_tec_i(&mut self) -> f64 {
+    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))
     }
-
-    pub fn fan_summary(&mut self, tacho: Option<u32>) -> Result<JsonBuffer, serde_json_core::ser::Error> {
-        if self.fan_available() {
-            let summary = FanSummary {
-                fan_pwm: self.get_fan_pwm(),
-                tacho: tacho.unwrap_or(u32::MAX),
-                abs_max_tec_i: self.current_abs_max_tec_i(),
-                auto_mode: self.fan_auto
-            };
-            serde_json_core::to_vec(&summary)
-        } else {
-            let summary: Option<()> = None;
-            serde_json_core::to_vec(&summary)
-        }
-    }
-
-    pub fn fan_ctrl(&mut self) {
-        if self.fan_auto && self.fan_available() {
-            let scaled_current = self.current_abs_max_tec_i() / MAX_TEC_I;
-            let pwm = max_by(scaled_current * scaled_current * MAX_FAN_PWM,
-                             MIN_FAN_PWM,
-                             |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal)) as u32;
-            self.set_fan_pwm(pwm);
-        }
-    }
 }
 
-type JsonBuffer = Vec<u8, U1024>;
+pub type JsonBuffer = Vec<u8, U1024>;
 
 #[derive(Serialize)]
 pub struct Report {
@@ -670,11 +603,3 @@ pub struct SteinhartHartSummary {
     channel: usize,
     params: steinhart_hart::Parameters,
 }
-
-#[derive(Serialize)]
-pub struct FanSummary {
-    fan_pwm: u32,
-    tacho: u32,
-    abs_max_tec_i: f64,
-    auto_mode: bool,
-}

src/command_handler.rs

@@ -22,7 +22,8 @@ use super::{
     config::ChannelConfig,
     dfu,
     flash_store::FlashStore,
-    session::Session
+    session::Session,
+    FanCtrl,
 };
 
 use uom::{
@@ -199,9 +200,6 @@ impl Handler {
                 let current = ElectricCurrent::new::<ampere>(value);
                 channels.set_max_i_neg(channel, current);
             }
-            PwmPin::Fan => {
-                channels.set_fan_pwm(value as u32);
-            }
         }
         send_line(socket, b"{}");
         Ok(Handler::Handled)
@@ -344,14 +342,14 @@ impl Handler {
         Ok(Handler::Reset)
     }
 
-    fn fan (socket: &mut TcpSocket, channels: &mut Channels, fan_pwm: Option<u32>, tacho_value: Option<u32>) -> Result<Handler, Error> {
+    fn fan (socket: &mut TcpSocket, fan_pwm: Option<u32>, fan_ctrl: &mut FanCtrl) -> Result<Handler, Error> {
         match fan_pwm {
             Some(val) => {
-                channels.set_fan_auto_mode(val == 0);
+                fan_ctrl.set_auto_mode(val == 0);
-                channels.set_fan_pwm(val);
+                fan_ctrl.set_pwm(val);
             },
             None => {
-                match channels.fan_summary(tacho_value) {
+                match fan_ctrl.summary() {
                     Ok(buf) => {
                         send_line(socket, &buf);
                         return Ok(Handler::Handled);
@@ -368,7 +366,19 @@ impl Handler {
         Ok(Handler::Handled)
     }
 
-    pub fn handle_command (command: Command, socket: &mut TcpSocket, channels: &mut Channels, session: &Session, leds: &mut Leds, store: &mut FlashStore, ipv4_config: &mut Ipv4Config, tacho_value: Option<u32>) -> Result<Self, Error> {
+    fn fan_coeff (socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl, k_a: f64, k_b: f64, k_c: f64) -> Result<Handler, Error> {
+        fan_ctrl.set_coefficients(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)
+    }
+
+    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) -> Result<Self, Error> {
         match command {
             Command::Quit => Ok(Handler::CloseSocket),
             Command::Reporting(_reporting) => Handler::reporting(socket),            
@@ -391,7 +401,9 @@ impl Handler {
             Command::Ipv4(config) => Handler::set_ipv4(socket, store, config),
             Command::Reset => Handler::reset(channels),
             Command::Dfu => Handler::dfu(channels),
-            Command::Fan {fan_pwm} => Handler::fan(socket, channels, fan_pwm, tacho_value)
+            Command::Fan {fan_pwm} => Handler::fan(socket, fan_pwm, fan_ctrl),
+            Command::FanCoeff { k_a, k_b, k_c } => Handler::fan_coeff(socket, fan_ctrl, k_a, k_b, k_c),
+            Command::FanDefaults => Handler::fan_defaults(socket, fan_ctrl),
         }
     }
 }

src/command_parser.rs

@@ -1,16 +1,7 @@
 use core::fmt;
 use core::num::ParseIntError;
 use core::str::{from_utf8, Utf8Error};
-use nom::{
+use nom::{IResult, branch::alt, bytes::complete::{is_a, tag, take_while1}, character::{is_digit, complete::{char, one_of}}, combinator::{complete, map, opt, value}, sequence::preceded, multi::{fold_many0, fold_many1}, error::ErrorKind, Needed};
-    IResult,
-    branch::alt,
-    bytes::complete::{is_a, tag, take_while1},
-    character::{is_digit, complete::{char, one_of}},
-    combinator::{complete, map, opt, value},
-    sequence::preceded,
-    multi::{fold_many0, fold_many1},
-    error::ErrorKind,
-};
 use num_traits::{Num, ParseFloatError};
 use serde::{Serialize, Deserialize};
 
@@ -127,7 +118,6 @@ pub enum PwmPin {
     MaxIPos,
     MaxINeg,
     MaxV,
-    Fan
 }
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
@@ -181,7 +171,13 @@ pub enum Command {
     Dfu,
     Fan {
         fan_pwm: Option<u32>
-    }
+    },
+    FanCoeff {
+        k_a: f64,
+        k_b: f64,
+        k_c: f64,
+    },
+    FanDefaults,
 }
 
 fn end(input: &[u8]) -> IResult<&[u8], ()> {
@@ -540,6 +536,33 @@ fn fan(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     Ok((input, result))
 }
 
+fn fan_coeff(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+    let (input, _) = tag("fcurve")(input)?;
+    let (input, coeffs) = alt((
+        |input| {
+            let (input, _) = whitespace(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)?;
+            let (input, _) = end(input)?;
+            if k_a.is_ok() && k_b.is_ok() && k_c.is_ok() {
+                Ok((input, Some((k_a.unwrap(), k_b.unwrap(), k_c.unwrap()))))
+            } else {
+                Err(nom::Err::Incomplete(Needed::Size(3)))
+            }
+        },
+        value(None, end)
+    ))(input)?;
+
+    let result = match coeffs {
+        Some(coeffs) => Ok(Command::FanCoeff { k_a: coeffs.0, k_b: coeffs.1, k_c: coeffs.2 }),
+        None => Err(Error::ParseFloat)
+    };
+    Ok((input, result))
+}
+
 fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     alt((value(Ok(Command::Quit), tag("quit")),
          load,
@@ -553,7 +576,9 @@ fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
          steinhart_hart,
          postfilter,
          value(Ok(Command::Dfu), tag("dfu")),
+         value(Ok(Command::FanDefaults), tag("fan-restore")),
          fan,
+         fan_coeff,
     ))(input)
 }
 

src/fan_ctrl.rs

@@ -0,0 +1,218 @@
+use core::{cmp::max_by};
+use serde::Serialize;
+use stm32f4xx_hal::{
+    pwm::{self, PwmChannels},
+    pac::TIM8,
+    gpio::{
+        Floating, Input, ExtiPin,
+        gpioc::PC8, Edge,
+    },
+    stm32::EXTI,
+    syscfg::{SysCfg},
+};
+use smoltcp::time::Instant;
+
+use crate::{
+    pins::HWRevPins,
+    channels::{Channels, JsonBuffer},
+    timer
+};
+
+pub type FanPin = PwmChannels<TIM8, pwm::C4>;
+pub type TachoPin = PC8<Input<Floating>>;
+
+const MAX_TEC_I: f64 = 3.0;
+// as stated in the schematics
+const MAX_FAN_PWM: f64 = 100.0;
+const MIN_FAN_PWM: f64 = 1.0;
+const TACHO_MEASURE_MS: i64 = 2500;
+const DEFAULT_K_A: f64 = 1.0;
+const DEFAULT_K_B: f64 = 0.0;
+const DEFAULT_K_C: f64 = 0.0;
+
+#[derive(Serialize, Copy, Clone)]
+pub struct HWRev {
+    pub major: u8,
+    pub minor: u8,
+}
+
+struct TachoCtrl {
+    tacho: TachoPin,
+    tacho_cnt: u32,
+    tacho_value: Option<u32>,
+    prev_epoch: i64,
+}
+
+pub struct FanCtrl<'a> {
+    fan: FanPin,
+    tacho: TachoCtrl,
+    fan_auto: bool,
+    available: bool,
+    k_a: f64,
+    k_b: f64,
+    k_c: f64,
+    channels: &'a mut Channels,
+}
+
+impl<'a> FanCtrl<'a> {
+    pub fn new(mut fan: FanPin, tacho: TachoPin, channels: &'a mut Channels, exti: &mut EXTI, syscfg: &mut SysCfg) -> Self {
+        let available = channels.hwrev.fan_available();
+
+        let mut tacho_ctrl = TachoCtrl::new(tacho);
+        if available {
+            fan.set_duty(0);
+            fan.enable();
+            tacho_ctrl.init(exti, syscfg);
+        }
+
+        FanCtrl {
+            fan,
+            tacho: tacho_ctrl,
+            available,
+            fan_auto: true,
+            k_a: DEFAULT_K_A,
+            k_b: DEFAULT_K_B,
+            k_c: DEFAULT_K_C,
+            channels,
+        }
+    }
+
+    pub fn cycle(&mut self) {
+        if self.available {
+            self.tacho.cycle();
+        }
+        self.adjust_speed();
+    }
+
+    pub fn summary(&mut self) -> Result<JsonBuffer, serde_json_core::ser::Error> {
+        if self.available {
+            let summary = FanSummary {
+                fan_pwm: self.get_pwm(),
+                tacho: self.tacho.get(),
+                abs_max_tec_i: self.channels.current_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 adjust_speed(&mut self) {
+        if self.fan_auto && self.available {
+            let scaled_current = self.channels.current_abs_max_tec_i() / MAX_TEC_I;
+            // do not limit upper bound, as it will be limited in the set_pwm()
+            let pwm = max_by(MAX_FAN_PWM * (scaled_current * (scaled_current * self.k_a + self.k_b) + self.k_c),
+                             MIN_FAN_PWM,
+                             |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal)) as u32;
+            self.set_pwm(pwm);
+        }
+    }
+
+    #[inline]
+    pub fn set_auto_mode(&mut self, fan_auto: bool) {
+        self.fan_auto = fan_auto;
+    }
+
+    #[inline]
+    pub fn set_coefficients(&mut self, k_a: f64, k_b: f64, k_c: f64) {
+        self.k_a = k_a;
+        self.k_b = k_b;
+        self.k_c = k_c;
+    }
+
+    #[inline]
+    pub fn restore_defaults(&mut self) {
+        self.set_auto_mode(true);
+        self.set_coefficients(DEFAULT_K_A, DEFAULT_K_B, DEFAULT_K_C);
+    }
+
+    pub fn set_pwm(&mut self, fan_pwm: u32) -> f64 {
+        let duty = fan_pwm as f64 / MAX_FAN_PWM;
+        let max = self.fan.get_max_duty();
+        let value = ((duty * (max as f64)) as u16).min(max);
+        self.fan.set_duty(value);
+        value as f64 / (max as f64)
+    }
+
+    fn get_pwm(&self) -> u32 {
+        let duty = self.fan.get_duty();
+        let max = self.fan.get_max_duty();
+        ((duty as f64 / (max as f64)) * MAX_FAN_PWM) as u32
+    }
+}
+
+impl TachoCtrl {
+    pub fn new(tacho: TachoPin) -> Self {
+        TachoCtrl {
+            tacho,
+            tacho_cnt: 0,
+            tacho_value: None,
+            prev_epoch: 0,
+        }
+    }
+
+    pub fn init(&mut self, exti: &mut EXTI, syscfg: &mut SysCfg) {
+        // These lines do not cause NVIC to run the ISR,
+        // since the interrupt should be unmasked in the cortex_m::peripheral::NVIC.
+        // Also using interrupt-related workaround is the best
+        // option for the current version of stm32f4xx-hal,
+        // since tying the IC's PC8 with the PWM's PC9 to the same TIM8 is not supported,
+        // and therefore would require even more weirder and unsafe hacks.
+        // Also such hacks wouldn't guarantee it to be more precise.
+        self.tacho.make_interrupt_source(syscfg);
+        self.tacho.trigger_on_edge(exti, Edge::Rising);
+        self.tacho.enable_interrupt(exti);
+    }
+
+    pub fn cycle(&mut self) {
+        let tacho_input = self.tacho.check_interrupt();
+        if tacho_input {
+            self.tacho.clear_interrupt_pending_bit();
+            self.tacho_cnt += 1;
+        }
+
+        let instant = Instant::from_millis(i64::from(timer::now()));
+        if instant.millis - self.prev_epoch >= TACHO_MEASURE_MS {
+            self.tacho_value = Some(self.tacho_cnt);
+            self.tacho_cnt = 0;
+            self.prev_epoch = instant.millis;
+        }
+    }
+
+    pub fn get(&self) -> u32 {
+        self.tacho_value.unwrap_or(u32::MAX)
+    }
+}
+
+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 fan_available(&self) -> bool {
+        self.major == 2 && self.minor == 2
+    }
+}
+
+#[derive(Serialize)]
+pub struct FanSummary {
+    fan_pwm: u32,
+    tacho: u32,
+    abs_max_tec_i: f64,
+    auto_mode: bool,
+    k_a: f64,
+    k_b: f64,
+    k_c: f64,
+}

src/main.rs

@@ -10,7 +10,7 @@ use panic_abort as _;
 use panic_semihosting as _;
 
 use log::{error, info, warn};
-
+use core::cell::RefCell;
 use cortex_m::asm::wfi;
 use cortex_m_rt::entry;
 use stm32f4xx_hal::{
@@ -19,7 +19,6 @@ use stm32f4xx_hal::{
     stm32::{CorePeripherals, Peripherals, SCB},
     time::{U32Ext, MegaHertz},
     watchdog::IndependentWatchdog,
-    gpio::{Edge, ExtiPin},
     syscfg::SysCfgExt
 };
 use smoltcp::{
@@ -56,6 +55,8 @@ mod flash_store;
 mod dfu;
 mod command_handler;
 use command_handler::Handler;
+mod fan_ctrl;
+use fan_ctrl::FanCtrl;
 
 const HSE: MegaHertz = MegaHertz(8);
 #[cfg(not(feature = "semihosting"))]
@@ -120,7 +121,7 @@ fn main() -> ! {
 
     timer::setup(cp.SYST, clocks);
 
-    let (pins, mut leds, mut eeprom, eth_pins, usb, mut tacho) = Pins::setup(
+    let (pins, mut leds, mut eeprom, eth_pins, usb, fan, tacho) = Pins::setup(
         clocks, dp.TIM1, dp.TIM3, dp.TIM8,
         dp.GPIOA, dp.GPIOB, dp.GPIOC, dp.GPIOD, dp.GPIOE, dp.GPIOF, dp.GPIOG,
         dp.I2C1,
@@ -137,22 +138,22 @@ fn main() -> ! {
 
     usb::State::setup(usb);
 
+    let mut channels = RefCell::new(Channels::new(pins));
+
     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]) {
             Ok(Some(config)) =>
-                config.apply(&mut channels, c),
+                config.apply(channels.get_mut(), c),
             Ok(None) =>
                 error!("flash config not found for channel {}", c),
             Err(e) =>
                 error!("unable to load config {} from flash: {:?}", c, e),
         }
     }
-
+    // considered safe since `channels` is being mutated in a single thread,
-    let fan_available = channels.fan_available();
+    // while mutex would be excessive
+    let mut fan_ctrl = FanCtrl::new(fan, tacho, unsafe{ &mut *channels.as_ptr() }, &mut dp.EXTI, &mut dp.SYSCFG.constrain());
 
     // default net config:
     let mut ipv4_config = Ipv4Config {
@@ -174,54 +175,22 @@ fn main() -> ! {
     let hwaddr = EthernetAddress(eui48);
     info!("EEPROM MAC address: {}", hwaddr);
 
-    if fan_available {
-        // These lines do not cause NVIC to run the ISR,
-        // since the interrupt should be unmasked in the cortex_m::peripheral::NVIC.
-        // Also using interrupt-related workaround is the best
-        // option for the current version of stm32f4xx-hal,
-        // since tying the IC's PC8 with the PWM's PC9 to the same TIM8 is not supported,
-        // and therefore would require even more weirder and unsafe hacks.
-        // Also such hacks wouldn't guarantee it to be more precise.
-        tacho.make_interrupt_source(&mut dp.SYSCFG.constrain());
-        tacho.trigger_on_edge(&mut dp.EXTI, Edge::Rising);
-        tacho.enable_interrupt(&mut dp.EXTI);
-    }
-
     net::run(clocks, dp.ETHERNET_MAC, dp.ETHERNET_DMA, eth_pins, hwaddr, ipv4_config.clone(), |iface| {
         Server::<Session>::run(iface, |server| {
             leds.r1.off();
             let mut should_reset = false;
 
-            let (mut tacho_cnt, mut tacho_value) = (0u32, None);
-            let mut prev_epoch: i64 = 0;
-
             loop {
                 let mut new_ipv4_config = None;
                 let instant = Instant::from_millis(i64::from(timer::now()));
-                let updated_channel = channels.poll_adc(instant);
+                let updated_channel = channels.get_mut().poll_adc(instant);
                 if let Some(channel) = updated_channel {
                     server.for_each(|_, session| session.set_report_pending(channel.into()));
                 }
+                fan_ctrl.cycle();
 
                 let instant = Instant::from_millis(i64::from(timer::now()));
 
-                if fan_available {
-                    let tacho_input = tacho.check_interrupt();
-                    if tacho_input {
-                        tacho.clear_interrupt_pending_bit();
-                        tacho_cnt += 1;
-                    }
-
-                    let epoch = instant.secs();
-                    if epoch > prev_epoch {
-                        tacho_value = Some(tacho_cnt);
-                        tacho_cnt = 0;
-                        prev_epoch = epoch;
-                    }
-                }
-
-                channels.fan_ctrl();
-
                 cortex_m::interrupt::free(net::clear_pending);
                 server.poll(instant)
                     .unwrap_or_else(|e| {
@@ -244,7 +213,7 @@ 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, tacho_value) {
+                                    match Handler::handle_command(command, &mut socket, channels.get_mut(), session, &mut leds, &mut store, &mut ipv4_config, &mut fan_ctrl) {
                                         Ok(Handler::NewIPV4(ip)) => new_ipv4_config = Some(ip),                                
                                         Ok(Handler::Handled) => {},
                                         Ok(Handler::CloseSocket) => socket.close(),
@@ -261,7 +230,7 @@ fn main() -> ! {
                             }
                         } else if socket.can_send() {
                             if let Some(channel) = session.is_report_pending() {
-                                match channels.reports_json() {
+                                match channels.get_mut().reports_json() {
                                     Ok(buf) => {
                                         send_line(&mut socket, &buf[..]);
                                         session.mark_report_sent(channel);

src/pins.rs

@@ -26,15 +26,18 @@ use stm32f4xx_hal::{
         TIM1, TIM3, TIM8
     },
     timer::Timer,
-    time::U32Ext,
+    time::{U32Ext, KiloHertz},
 };
 use eeprom24x::{self, Eeprom24x};
 use stm32_eth::EthPins;
 use crate::{
     channel::{Channel0, Channel1},
     leds::Leds,
+    fan_ctrl::{TachoPin, FanPin}
 };
 
+const PWM_FREQ: KiloHertz = KiloHertz(20u32);
+
 pub type Eeprom = Eeprom24x<
     I2c<I2C1, (
         PB8<AlternateOD<{ stm32f4xx_hal::gpio::AF4 }>>,
@@ -128,7 +131,7 @@ impl Pins {
         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, PC8<Input<Floating>>) {
+    ) -> (Self, Leds, Eeprom, EthernetPins, USB, FanPin, TachoPin) {
         let gpioa = gpioa.split();
         let gpiob = gpiob.split();
         let gpioc = gpioc.split();
@@ -143,10 +146,10 @@ impl Pins {
         let pins_adc = Adc::adc1(adc1, true, Default::default());
 
         let pwm = PwmPins::setup(
-            clocks, tim1, tim3, tim8,
+            clocks, tim1, tim3,
             gpioc.pc6, gpioc.pc7,
             gpioe.pe9, gpioe.pe11,
-            gpioe.pe13, gpioe.pe14, gpioc.pc9
+            gpioe.pe13, gpioe.pe14
         );
 
         let (dac0_spi, dac0_sync) = Self::setup_dac0(
@@ -225,7 +228,9 @@ impl Pins {
             hclk: clocks.hclk(),
         };
 
-        (pins, leds, eeprom, eth_pins, usb, gpioc.pc8)
+        let fan = Timer::new(tim8, &clocks).pwm(gpioc.pc9.into_alternate(), 20u32.khz());
+
+        (pins, leds, eeprom, eth_pins, usb, fan, gpioc.pc8)
     }
 
     /// Configure the GPIO pins for SPI operation, and initialize SPI
@@ -293,24 +298,20 @@ pub struct PwmPins {
     pub max_i_pos1: PwmChannels<TIM1, pwm::C2>,
     pub max_i_neg0: PwmChannels<TIM1, pwm::C3>,
     pub max_i_neg1: PwmChannels<TIM1, pwm::C4>,
-    pub fan: PwmChannels<TIM8, pwm::C4>,
 }
 
 impl PwmPins {
-    fn setup<M1, M2, M3, M4, M5, M6, M7>(
+    fn setup<M1, M2, M3, M4, M5, M6>(
         clocks: Clocks,
         tim1: TIM1,
         tim3: TIM3,
-        tim8: TIM8,
         max_v0: PC6<M1>,
         max_v1: PC7<M2>,
         max_i_pos0: PE9<M3>,
         max_i_pos1: PE11<M4>,
         max_i_neg0: PE13<M5>,
         max_i_neg1: PE14<M6>,
-        fan: PC9<M7>,
     ) -> PwmPins {
-        let freq = 20u32.khz();
 
         fn init_pwm_pin<P: hal::PwmPin<Duty=u16>>(pin: &mut P) {
             pin.set_duty(0);
@@ -320,14 +321,11 @@ impl PwmPins {
             max_v0.into_alternate(),
             max_v1.into_alternate(),
         );
-        //let (mut max_v0, mut max_v1) = pwm::tim3(tim3, channels, clocks, freq);
+        //let (mut max_v0, mut max_v1) = pwm::tim3(tim3, channels, clocks, PWM_FREQ);
-        let (mut max_v0, mut max_v1) = Timer::new(tim3, &clocks).pwm(channels, freq);
+        let (mut max_v0, mut max_v1) = Timer::new(tim3, &clocks).pwm(channels, PWM_FREQ);
         init_pwm_pin(&mut max_v0);
         init_pwm_pin(&mut max_v1);
 
-        let mut fan = Timer::new(tim8, &clocks).pwm(fan.into_alternate(), freq);
-        init_pwm_pin(&mut fan);
-
         let channels = (
             max_i_pos0.into_alternate(),
             max_i_pos1.into_alternate(),
@@ -335,7 +333,7 @@ impl PwmPins {
             max_i_neg1.into_alternate(),
         );
         let (mut max_i_pos0, mut max_i_pos1, mut max_i_neg0, mut max_i_neg1) =
-            Timer::new(tim1, &clocks).pwm(channels, freq);
+            Timer::new(tim1, &clocks).pwm(channels, PWM_FREQ);
         init_pwm_pin(&mut max_i_pos0);
         init_pwm_pin(&mut max_i_neg0);
         init_pwm_pin(&mut max_i_pos1);
@@ -344,8 +342,7 @@ impl PwmPins {
         PwmPins {
             max_v0, max_v1,
             max_i_pos0, max_i_pos1,
-            max_i_neg0, max_i_neg1,
+            max_i_neg0, max_i_neg1
-            fan
         }
     }
 }