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                                                               |
@@ -126,8 +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)   |
+| `fcurve <a> <b> <c>`             | Set fan controller curve coefficients (see *Fan control* section)             |
+| `fcurve-restore`                 | Set fan controller curve coefficients to defaults (see *Fan control* section) |
 
 
 ## USB
@@ -286,4 +286,4 @@ 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 = 0.04`.
+4. `fcurve-restore` - restore fan settings to defaults: `auto = true, a = 1.0, b = 0.0, c = 0.00`.

src/command_handler.rs

@@ -366,8 +366,8 @@ impl Handler {
         Ok(Handler::Handled)
     }
 
-    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);
+    fn fan_curve(socket: &mut TcpSocket, fan_ctrl: &mut FanCtrl, k_a: f64, k_b: f64, k_c: f64) -> Result<Handler, Error> {
+        fan_ctrl.set_curve(k_a, k_b, k_c);
         send_line(socket, b"{}");
         Ok(Handler::Handled)
     }
@@ -378,31 +378,31 @@ 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, fan_ctrl: &mut FanCtrl) -> Result<Self, Error> {
+    pub fn handle_command(command: Command, socket: &mut TcpSocket, 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),            
             Command::Show(ShowCommand::Reporting) => Handler::show_report_mode(socket, session),            
-            Command::Show(ShowCommand::Input) => Handler::show_report(socket, channels),
-            Command::Show(ShowCommand::Pid) => Handler::show_pid(socket, channels),            
-            Command::Show(ShowCommand::Pwm) => Handler::show_pwm(socket, channels),
-            Command::Show(ShowCommand::SteinhartHart) => Handler::show_steinhart_hart(socket, channels),            
-            Command::Show(ShowCommand::PostFilter) => Handler::show_post_filter(socket, channels),            
+            Command::Show(ShowCommand::Input) => Handler::show_report(socket, &mut fan_ctrl.channels),
+            Command::Show(ShowCommand::Pid) => Handler::show_pid(socket, &mut fan_ctrl.channels),
+            Command::Show(ShowCommand::Pwm) => Handler::show_pwm(socket, &mut fan_ctrl.channels),
+            Command::Show(ShowCommand::SteinhartHart) => Handler::show_steinhart_hart(socket, &mut fan_ctrl.channels),
+            Command::Show(ShowCommand::PostFilter) => Handler::show_post_filter(socket, &mut fan_ctrl.channels),
             Command::Show(ShowCommand::Ipv4) => Handler::show_ipv4(socket, ipv4_config),
-            Command::PwmPid { channel } => Handler::engage_pid(socket, channels, leds, channel),
-            Command::Pwm { channel, pin, value } => Handler::set_pwm(socket, channels, leds, 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),
-            Command::SteinhartHart { channel, parameter, value } => Handler::set_steinhart_hart(socket, channels, channel, parameter, value),
-            Command::PostFilter { channel, rate: None } => Handler::reset_post_filter(socket, channels, channel),
-            Command::PostFilter { channel, rate: Some(rate) } => Handler::set_post_filter(socket, channels, channel, rate),
-            Command::Load { channel } => Handler::load_channel(socket, channels, store, channel),
-            Command::Save { channel } => Handler::save_channel(socket, channels, channel, store),
+            Command::PwmPid { channel } => Handler::engage_pid(socket, &mut fan_ctrl.channels, leds, channel),
+            Command::Pwm { channel, pin, value } => Handler::set_pwm(socket, &mut fan_ctrl.channels, leds, channel, pin, value),
+            Command::CenterPoint { channel, center } => Handler::set_center_point(socket, &mut fan_ctrl.channels, channel, center),
+            Command::Pid { channel, parameter, value } => Handler::set_pid(socket, &mut fan_ctrl.channels, channel, parameter, value),
+            Command::SteinhartHart { channel, parameter, value } => Handler::set_steinhart_hart(socket, &mut fan_ctrl.channels, channel, parameter, value),
+            Command::PostFilter { channel, rate: None } => Handler::reset_post_filter(socket, &mut fan_ctrl.channels, channel),
+            Command::PostFilter { channel, rate: Some(rate) } => Handler::set_post_filter(socket, &mut fan_ctrl.channels, channel, rate),
+            Command::Load { channel } => Handler::load_channel(socket, &mut fan_ctrl.channels, store, channel),
+            Command::Save { channel } => Handler::save_channel(socket, &mut fan_ctrl.channels, channel, store),
             Command::Ipv4(config) => Handler::set_ipv4(socket, store, config),
-            Command::Reset => Handler::reset(channels),
-            Command::Dfu => Handler::dfu(channels),
+            Command::Reset => Handler::reset(&mut fan_ctrl.channels),
+            Command::Dfu => Handler::dfu(&mut fan_ctrl.channels),
             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::FanCurve { k_a, k_b, k_c } => Handler::fan_curve(socket, fan_ctrl, k_a, k_b, k_c),
             Command::FanDefaults => Handler::fan_defaults(socket, fan_ctrl),
         }
     }

src/command_parser.rs

@@ -182,7 +182,7 @@ pub enum Command {
     Fan {
         fan_pwm: Option<u32>
     },
-    FanCoeff {
+    FanCurve {
         k_a: f64,
         k_b: f64,
         k_c: f64,
@@ -546,9 +546,9 @@ fn fan(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     Ok((input, result))
 }
 
-fn fan_coeff(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+fn fan_curve(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
     let (input, _) = tag("fcurve")(input)?;
-    let (input, coeffs) = alt((
+    let (input, curve) = alt((
         |input| {
             let (input, _) = whitespace(input)?;
             let (input, k_a) = float(input)?;
@@ -566,8 +566,8 @@ fn fan_coeff(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
         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 }),
+    let result = match curve {
+        Some(curve) => Ok(Command::FanCurve { k_a: curve.0, k_b: curve.1, k_c: curve.2 }),
         None => Err(Error::ParseFloat)
     };
     Ok((input, result))
@@ -586,9 +586,9 @@ 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")),
+         value(Ok(Command::FanDefaults), tag("fcurve-restore")),
          fan,
-         fan_coeff,
+         fan_curve,
     ))(input)
 }
 

src/fan_ctrl.rs

@@ -1,4 +1,3 @@
-use core::{cmp::max_by};
 use serde::Serialize;
 use stm32f4xx_hal::{
     pwm::{self, PwmChannels},
@@ -21,15 +20,33 @@ use crate::{
 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 MAX_TEC_I: f64 = 3.0;
+
+const MAX_USER_FAN_PWM: f64 = 100.0;
+const MIN_USER_FAN_PWM: f64 = 1.0;
+const MAX_FAN_PWM: f64 = 1.0;
+// below this value, motor pulse signal is too weak to be registered by tachometer
+const MIN_FAN_PWM: f64 = 0.05;
+
 const TACHO_MEASURE_MS: i64 = 2500;
-const TACHO_LOW_THRESHOLD: u32 = 100;
+// by default up to 2 cycles are skipped on changes in PWM output,
+// and the halt threshold will help detect the failure during these skipped cycles
+const TACHO_HALT_THRESHOLD: u32 = 250;
+const TACHO_SKIP_CYCLES: u8 = 2;
+
 const DEFAULT_K_A: f64 = 1.0;
 const DEFAULT_K_B: f64 = 0.0;
-const DEFAULT_K_C: f64 = 0.04;
+const DEFAULT_K_C: f64 = 0.0;
+
+// This regression is from 6% to 25% lower than values registered in the experiments.
+// Actual values would be better estimated by logarithmic regression, but that would require more
+// runtime computation, and wouldn't give significant correlation difference
+// (0.996 for log and 0.966 for quadratic regression).
+const TACHO_REGRESSION_A: f64 = -0.04135128436;
+const TACHO_REGRESSION_B: f64 = 6.23015531;
+const TACHO_REGRESSION_C: f64 = 403.6833577;
+
 
 #[derive(Serialize, Copy, Clone)]
 pub struct HWRev {
@@ -41,8 +58,8 @@ pub struct HWRev {
 pub enum FanStatus {
     OK,
     NotAvailable,
-    Stalled,
-    LowSignal,
+    TooSlow,
+    Halted
 }
 
 struct TachoCtrl {
@@ -50,10 +67,9 @@ struct TachoCtrl {
     tacho_cnt: u32,
     tacho_value: Option<u32>,
     prev_epoch: i64,
-    past_record: u64,
 }
 
-pub struct FanCtrl<'a> {
+pub struct FanCtrl {
     fan: FanPin,
     tacho: TachoCtrl,
     fan_auto: bool,
@@ -61,12 +77,13 @@ pub struct FanCtrl<'a> {
     k_a: f64,
     k_b: f64,
     k_c: f64,
-    channels: &'a mut Channels,
-    last_status: FanStatus
+    pub channels: Channels,
+    last_status: FanStatus,
+    skip_cycles: u8,
 }
 
-impl<'a> FanCtrl<'a> {
-    pub fn new(mut fan: FanPin, tacho: TachoPin, channels: &'a mut Channels, exti: &mut EXTI, syscfg: &mut SysCfg) -> Self {
+impl FanCtrl {
+    pub fn new(mut fan: FanPin, tacho: TachoPin, channels: Channels, exti: &mut EXTI, syscfg: &mut SysCfg) -> Self {
         let available = channels.hwrev.fan_available();
 
         let mut tacho_ctrl = TachoCtrl::new(tacho);
@@ -85,17 +102,20 @@ impl<'a> FanCtrl<'a> {
             k_b: DEFAULT_K_B,
             k_c: DEFAULT_K_C,
             channels,
-            last_status: FanStatus::OK,
+            last_status: if available { FanStatus::OK } else { FanStatus::NotAvailable },
+            skip_cycles: 0
         }
     }
 
     pub fn cycle(&mut self) -> Result<(), FanStatus> {
         if self.available {
-            self.tacho.cycle();
+            if self.tacho.cycle() {
+                self.skip_cycles >>= 1;
+            }
         }
         self.adjust_speed();
         let diagnose = self.diagnose();
-        if diagnose != self.last_status {
+        if (self.skip_cycles == 0 || diagnose == FanStatus::Halted) && diagnose != self.last_status {
             self.last_status = diagnose;
             Err(diagnose)
         } else {
@@ -126,9 +146,7 @@ impl<'a> FanCtrl<'a> {
         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;
+            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);
         }
     }
@@ -139,7 +157,7 @@ impl<'a> FanCtrl<'a> {
     }
 
     #[inline]
-    pub fn set_coefficients(&mut self, k_a: f64, k_b: f64, k_c: f64) {
+    pub fn set_curve(&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;
@@ -148,28 +166,50 @@ impl<'a> FanCtrl<'a> {
     #[inline]
     pub fn restore_defaults(&mut self) {
         self.set_auto_mode(true);
-        self.set_coefficients(DEFAULT_K_A, DEFAULT_K_B, DEFAULT_K_C);
+        self.set_curve(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 fan_pwm = fan_pwm.min(MAX_USER_FAN_PWM as u32).max(MIN_USER_FAN_PWM as u32);
+        self.skip_cycles = if (self.tacho.get() as f64) <= Self::threshold_for_pwm(fan_pwm as f64) {
+            TACHO_SKIP_CYCLES
+        } else { self.skip_cycles };
+        let duty = Self::scale_number(fan_pwm as f64, MIN_FAN_PWM, MAX_FAN_PWM, MIN_USER_FAN_PWM, MAX_USER_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)
     }
 
+    #[inline]
+    fn threshold_for_pwm(fan_pwm: f64) -> f64 {
+        (TACHO_REGRESSION_A * fan_pwm + TACHO_REGRESSION_B) * fan_pwm + TACHO_REGRESSION_C
+    }
+
+    #[inline]
+    fn scale_number(unscaled: f64, to_min: f64, to_max: f64, from_min: f64, from_max: f64) -> f64 {
+        (to_max - to_min) * (unscaled - from_min) / (from_max - from_min) + to_min
+    }
+
     fn diagnose(&mut self) -> FanStatus {
         if !self.available {
             return FanStatus::NotAvailable;
         }
-        self.tacho.diagnose()
+        let threshold = Self::threshold_for_pwm(self.get_pwm() as f64) as u32;
+        let tacho = self.tacho.get();
+        if tacho >= threshold {
+            FanStatus::OK
+        } else if tacho >= TACHO_HALT_THRESHOLD {
+            FanStatus::TooSlow
+        } else {
+            FanStatus::Halted
+        }
     }
 
     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
+        (Self::scale_number(duty as f64 / (max as f64), MIN_USER_FAN_PWM, MAX_USER_FAN_PWM, MIN_FAN_PWM, MAX_FAN_PWM) + 0.5) as u32
     }
 }
 
@@ -180,34 +220,24 @@ impl TachoCtrl {
             tacho_cnt: 0,
             tacho_value: None,
             prev_epoch: 0,
-            past_record: 0,
         }
     }
 
     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.
+        // since the interrupt is masked 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.
+        // since tying the IC's PC8 with the PWM's PC9 to the same TIM8 is not supported.
+        // The possible solution would be to update the library to >=v0.14.*,
+        // and use its Timer's counter functionality.
         self.tacho.make_interrupt_source(syscfg);
         self.tacho.trigger_on_edge(exti, Edge::Rising);
         self.tacho.enable_interrupt(exti);
     }
 
-    #[inline]
-    fn add_record(&mut self, value: u32) {
-        self.past_record = self.past_record << 2;
-        if value >= TACHO_LOW_THRESHOLD {
-            self.past_record += 0b11;
-        } else if value > 0 && self.tacho_cnt < TACHO_LOW_THRESHOLD {
-            self.past_record += 0b10;
-        }
-    }
-
-    fn cycle(&mut self) {
+    // returns whether the epoch elapsed
+    fn cycle(&mut self) -> bool {
         let tacho_input = self.tacho.check_interrupt();
         if tacho_input {
             self.tacho.clear_interrupt_pending_bit();
@@ -217,25 +247,17 @@ impl TachoCtrl {
         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.add_record(self.tacho_cnt);
             self.tacho_cnt = 0;
             self.prev_epoch = instant.millis;
+            true
+        } else {
+            false
         }
     }
 
     fn get(&self) -> u32 {
         self.tacho_value.unwrap_or(u32::MAX)
     }
-
-    fn diagnose(&mut self) -> FanStatus {
-        if self.past_record & 0b11 == 0b11 {
-            FanStatus::OK
-        } else if self.past_record & 0xAAAAAAAAAAAAAAAA > 0 {
-            FanStatus::LowSignal
-        } else {
-            FanStatus::Stalled
-        }
-    }
 }
 
 impl HWRev {
@@ -272,8 +294,23 @@ impl FanStatus {
         match *self {
             FanStatus::OK => "Fan is OK".as_bytes(),
             FanStatus::NotAvailable => "Fan is not available".as_bytes(),
-            FanStatus::Stalled => "Fan is stalled".as_bytes(),
-            FanStatus::LowSignal => "Fan is low signal".as_bytes(),
+            FanStatus::TooSlow => "Fan is too slow".as_bytes(),
+            FanStatus::Halted => "Fan is halted".as_bytes(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_scaler() {
+        for x in 1..100 {
+            assert_eq!((FanCtrl::scale_number(
+                FanCtrl::scale_number(x as f64, MIN_FAN_PWM, MAX_FAN_PWM, MIN_USER_FAN_PWM, MAX_USER_FAN_PWM),
+                                              MIN_USER_FAN_PWM, MAX_USER_FAN_PWM, MIN_FAN_PWM, MAX_FAN_PWM) + 0.5) as i32,
+                       x);
         }
     }
 }

src/main.rs

@@ -10,7 +10,6 @@ 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::{
@@ -140,20 +139,19 @@ fn main() -> ! {
 
     let mut store = flash_store::store(dp.FLASH);
 
-    let mut channels = RefCell::new(Channels::new(pins));
+    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(channels.get_mut(), c),
+                config.apply(&mut channels, 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,
-    // 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());
+
+    let mut fan_ctrl = FanCtrl::new(fan, tacho, channels, &mut dp.EXTI, &mut dp.SYSCFG.constrain());
 
     // default net config:
     let mut ipv4_config = Ipv4Config {
@@ -183,7 +181,7 @@ fn main() -> ! {
             loop {
                 let mut new_ipv4_config = None;
                 let instant = Instant::from_millis(i64::from(timer::now()));
-                let updated_channel = channels.get_mut().poll_adc(instant);
+                let updated_channel = fan_ctrl.channels.poll_adc(instant);
                 if let Some(channel) = updated_channel {
                     server.for_each(|_, session| session.set_report_pending(channel.into()));
                 }
@@ -213,7 +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, channels.get_mut(), session, &mut leds, &mut store, &mut ipv4_config, &mut fan_ctrl) {
+                                    match Handler::handle_command(command, &mut socket, 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(),
@@ -230,7 +228,7 @@ fn main() -> ! {
                             }
                         } else if socket.can_send() {
                             if let Some(channel) = session.is_report_pending() {
-                                match channels.get_mut().reports_json() {
+                                match fan_ctrl.channels.reports_json() {
                                     Ok(buf) => {
                                         send_line(&mut socket, &buf[..]);
                                         session.mark_report_sent(channel);