From 00d5feaa8d8c46617fd6c7c38f5f469af5aa67bd Mon Sep 17 00:00:00 2001
From: atse <atse@m-labs.hk>
Date: Wed, 3 Apr 2024 11:31:34 +0800
Subject: [PATCH] Limit i_set within range of MAX1968 chip

---
 src/channels.rs | 9 +++++++++
 src/fan_ctrl.rs | 6 ++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/channels.rs b/src/channels.rs
index 70ef7a0..488a8d6 100644
--- a/src/channels.rs
+++ b/src/channels.rs
@@ -25,6 +25,10 @@ use crate::{
 
 pub const CHANNELS: usize = 2;
 pub const R_SENSE: f64 = 0.05;
+
+// as stated in the MAX1968 datasheet
+pub const MAX_TEC_I: f64 = 3.0;
+
 // 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;
 
@@ -130,6 +134,11 @@ impl<'a> Channels<'a> {
     }
 
     pub fn set_i(&mut self, channel: usize, i_set: ElectricCurrent) -> ElectricCurrent {
+        // Silently clamp i_set
+        let i_ceiling = ElectricCurrent::new::<ampere>(MAX_TEC_I);
+        let i_floor = ElectricCurrent::new::<ampere>(-MAX_TEC_I);
+        let i_set = i_set.min(i_ceiling).max(i_floor);
+
         let vref_meas = match channel.into() {
             0 => self.channel0.vref_meas,
             1 => self.channel1.vref_meas,
diff --git a/src/fan_ctrl.rs b/src/fan_ctrl.rs
index 30416f3..614510b 100644
--- a/src/fan_ctrl.rs
+++ b/src/fan_ctrl.rs
@@ -11,13 +11,11 @@ use uom::si::{
 use crate::{
     hw_rev::HWSettings,
     command_handler::JsonBuffer,
+    channels::MAX_TEC_I,
 };
 
 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;
 
@@ -56,7 +54,7 @@ impl FanCtrl {
     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;
+            let scaled_current = self.abs_max_tec_i / MAX_TEC_I as f32;
             // 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);