Implemented auto fan control

Signed-off-by: Egor Savkin <es@m-labs.hk>

README.md

@@ -125,7 +125,7 @@ formatted as line-delimited JSON.
 | `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 |
 | `fan`                            | Show current fan settings and sensors' measurements                  |
-| `fan <value>`                    | Set fan power with values from 0 to 100, where 0 is auto mode (TODO) |
+| `fan <value>`                    | Set fan power with values from 0 to 100, where 0 is auto mode        |
 
 
 ## USB
@@ -271,3 +271,13 @@ 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 two 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.

src/channels.rs

@@ -26,6 +26,9 @@ 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 {
@@ -41,7 +44,8 @@ pub struct Channels {
     /// stm32f4 integrated adc
     pins_adc: pins::PinsAdc,
     pub pwm: pins::PwmPins,
-    pub hw_rev: HWRev
+    hw_rev: HWRev,
+    fan_auto: bool
 }
 
 impl Channels {
@@ -63,7 +67,8 @@ impl Channels {
         let channel1 = Channel::new(pins.channel1, adc_calibration1);
         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) };
+        let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm,
+            hw_rev: Self::detect_hw_rev(&pins.hwrev), fan_auto: true };
         for channel in 0..CHANNELS {
             channels.channel_state(channel).vref = channels.read_vref(channel);
             channels.calibrate_dac_value(channel);
@@ -407,7 +412,7 @@ impl Channels {
         (self.read_tec_u_meas(channel) - ElectricPotential::new::<volt>(1.5)) * 4.0
     }
 
-    pub fn set_pwm(&mut self, channel: usize, pin: PwmPin, duty: f64) -> f64 {
+    fn set_pwm(&mut self, channel: usize, pin: PwmPin, duty: f64) -> f64 {
         fn set<P: hal::PwmPin<Duty=u16>>(pin: &mut P, duty: f64) -> f64 {
             let max = pin.get_max_duty();
             let value = ((duty * (max as f64)) as u16).min(max);
@@ -458,12 +463,16 @@ impl Channels {
     }
 
     pub fn set_fan_pwm(&mut self, fan_pwm: u32) -> f64 {
-        let duty = fan_pwm as f64 / 100.0;
+        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) * 100.0) as 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 {
@@ -557,12 +566,19 @@ impl Channels {
         serde_json_core::to_vec(&summaries)
     }
 
+    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: max_by(self.get_tec_i(0).abs().value, self.get_tec_i(1).abs().value, |a, b| a.partial_cmp(b).unwrap())
+                abs_max_tec_i: self.current_abs_max_tec_i(),
+                auto_mode: self.fan_auto
             };
             serde_json_core::to_vec(&summary)
         } else {
@@ -570,6 +586,16 @@ impl Channels {
             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>;
@@ -650,4 +676,5 @@ pub struct FanSummary {
     fan_pwm: u32,
     tacho: u32,
     abs_max_tec_i: f64,
+    auto_mode: bool,
 }

src/command_handler.rs

@@ -347,13 +347,14 @@ impl Handler {
     fn fan (socket: &mut TcpSocket, channels: &mut Channels, fan_pwm: Option<u32>, tacho_value: Option<u32>) -> Result<Handler, Error> {
         match fan_pwm {
             Some(val) => {
+                channels.set_fan_auto_mode(val == 0);
                 channels.set_fan_pwm(val);
-                Ok(Handler::Handled)
             },
             None => {
                 match channels.fan_summary(tacho_value) {
                     Ok(buf) => {
                         send_line(socket, &buf);
+                        return Ok(Handler::Handled);
                     }
                     Err(e) => {
                         error!("unable to serialize fan summary: {:?}", e);
@@ -361,10 +362,11 @@ impl Handler {
                         return Err(Error::ReportError);
                     }
                 };
+            }
+        };
+        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, tacho_value: Option<u32>) -> Result<Self, Error> {
         match command {

src/command_parser.rs

@@ -303,8 +303,7 @@ fn pwm_setup(input: &[u8]) -> IResult<&[u8], Result<(PwmPin, f64), Error>> {
                 )
             ),
             result_with_pin(PwmPin::MaxV)
-        ),
+        ))
-    )
     )(input)
 }
 

src/main.rs

@@ -19,14 +19,14 @@ use stm32f4xx_hal::{
     stm32::{CorePeripherals, Peripherals, SCB},
     time::{U32Ext, MegaHertz},
     watchdog::IndependentWatchdog,
+    gpio::{Edge, ExtiPin},
+    syscfg::SysCfgExt
 };
 use smoltcp::{
     time::Instant,
     socket::TcpSocket,
     wire::EthernetAddress,
 };
-use stm32f4xx_hal::gpio::{Edge, ExtiPin};
-use stm32f4xx_hal::syscfg::SysCfgExt;
 
 mod init_log;
 use init_log::init_log;
@@ -220,6 +220,8 @@ fn main() -> ! {
                     }
                 }
 
+                channels.fan_ctrl();
+
                 cortex_m::interrupt::free(net::clear_pending);
                 server.poll(instant)
                     .unwrap_or_else(|e| {