Implement simple fan control

Core/Src/FanControl.c

@@ -1,18 +1,48 @@
 #include "FanControl.h"
 
+#include "TMP144.h"
+#include "main.h"
+
 #include "stm32f4xx_hal_def.h"
 #include "stm32f4xx_hal_tim.h"
 
+#include <stdint.h>
+
 TIM_HandleTypeDef* timer;
 uint32_t channel;
+FanState fan_state;
 
 HAL_StatusTypeDef fan_ctrl_init(TIM_HandleTypeDef* handle, uint32_t channel_) {
   timer = handle;
   channel = channel_;
+  fan_state = FANS_OFF;
 
   return HAL_TIM_PWM_Start(timer, channel);
 }
 
+void fan_ctrl_update() {
+  if (fan_state == FANS_OFF && max_temperature > THRESH_FANS_ON_HALF) {
+    fan_state = FANS_ON;
+  } else if (fan_state == FANS_ON && max_temperature < THRESH_FANS_OFF) {
+    fan_state = FANS_OFF;
+  }
+
+  uint32_t power;
+  if (fan_state == FANS_OFF) {
+    power = 0;
+  } else {
+    if (max_temperature < THRESH_FANS_ON_HALF) {
+      power = 50;
+    } else if (max_temperature > THRESH_FANS_ON_FULL) {
+      power = 100;
+    } else {
+      power = (100 * (max_temperature - THRESH_FANS_ON_HALF)) /
+              (THRESH_FANS_ON_FULL - THRESH_FANS_ON_HALF);
+    }
+  }
+  fan_ctrl_set_power(power);
+}
+
 void fan_ctrl_set_power(uint32_t percent) {
   if (percent > 100) {
     percent = 100;

Core/Src/main.c

@@ -188,6 +188,7 @@ int main(void) {
     afe_measure();
     tmp144_read_temps();
     check_error_conditions();
+    fan_ctrl_update();
     delay_period();
   }
   /* USER CODE END 3 */