From 8a583aaa8c1a27a3d13747b7ecead6a3d73a4e81 Mon Sep 17 00:00:00 2001
From: Robbe Derks <robbe.derks@gmail.com>
Date: Wed, 2 Apr 2025 12:15:35 +0200
Subject: [PATCH] Fan controller: fix instability on high rpm fans (#2179)

* integrator error relative to max rpm

* need to cast
---
 board/drivers/fan.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/board/drivers/fan.h b/board/drivers/fan.h
index b355f58b..ec0e1be5 100644
--- a/board/drivers/fan.h
+++ b/board/drivers/fan.h
@@ -19,7 +19,7 @@ void fan_init(void) {
 
 // Call this at FAN_TICK_FREQ
 void fan_tick(void) {
-  const float FAN_I = 0.001f;
+  const float FAN_I = 6.5f;
   const uint8_t FAN_STALL_THRESHOLD_MAX = 8U;
 
   if (current_board->fan_max_rpm > 0U) {
@@ -74,7 +74,7 @@ void fan_tick(void) {
     if (fan_state.target_rpm == 0U) {
       fan_state.error_integral = 0.0f;
     } else {
-      float error = fan_state.target_rpm - fan_rpm_fast;
+      float error = (fan_state.target_rpm - fan_rpm_fast) / ((float) current_board->fan_max_rpm);
       fan_state.error_integral += FAN_I * error;
     }
     fan_state.error_integral = CLAMP(fan_state.error_integral, 0U, current_board->fan_max_pwm);