README.md

@@ -277,12 +277,11 @@ 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 four commands are available:
+Fan control commands are available for thermostat revisions with an integrated fan system:
 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.
+2. `fan auto` - enable auto speed controller mode, where fan speed is controlled by the 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 completely 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`.
+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`, a normalized value in range [0,1],
+i.e. the (linear) proportion of current output capacity used, on the channel with the largest current flow. The controlling curve is also clamped to [0,1].
+5. `fcurve default` - restore fan curve coefficients to defaults: `a = 1.0, b = 0.0, c = 0.0`.

src/channels.rs

@@ -524,9 +524,9 @@ impl Channels {
         serde_json_core::to_vec(&summaries)
     }
 
-    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>(),
+    pub fn current_abs_max_tec_i(&mut self) -> ElectricCurrent {
+        max_by(self.get_tec_i(0).abs(),
+               self.get_tec_i(1).abs(),
                |a, b| a.partial_cmp(b).unwrap_or(core::cmp::Ordering::Equal))
     }
 }

src/fan_ctrl.rs

@@ -4,7 +4,10 @@ use stm32f4xx_hal::{
     pwm::{self, PwmChannels},
     pac::TIM8,
 };
-
+use uom::si::{
+    f64::ElectricCurrent,
+    electric_current::ampere,
+};
 use crate::{
     hw_rev::HWSettings,
     command_handler::JsonBuffer,
@@ -50,8 +53,8 @@ impl FanCtrl {
         fan_ctrl
     }
 
-    pub fn cycle(&mut self, abs_max_tec_i: f32) {
-        self.abs_max_tec_i = abs_max_tec_i;
+    pub fn cycle(&mut self, abs_max_tec_i: ElectricCurrent) {
+        self.abs_max_tec_i = abs_max_tec_i.get::<ampere>() as f32;
         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()

src/main.rs

@@ -185,7 +185,7 @@ fn main() -> ! {
                     server.for_each(|_, session| session.set_report_pending(channel.into()));
                 }
 
-                fan_ctrl.cycle(channels.current_abs_max_tec_i() as f32);
+                fan_ctrl.cycle(channels.current_abs_max_tec_i());
 
                 if channels.pid_engaged() {
                     leds.g3.on();