From 5bfe3890f28d0a62a6d18a8f63cc32c34234343a Mon Sep 17 00:00:00 2001
From: "Adrian A. Baumann" <ade@adebaumann.com>
Date: Sat, 27 Jun 2026 01:33:48 +0200
Subject: [PATCH] Detach freed PWM channels in attachMeters()

---
 src/main.cpp | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 6e23cb7..5a8700b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -138,12 +138,29 @@ static void saveConfig() {
 // PWM helpers
 // ---------------------------------------------------------------------------
 
+// Tracks the GPIO currently bound to each PWM channel so channels that get
+// freed (meter count shrinks, or a pin is changed/cleared) are detached
+// instead of being left driving PWM on their old pin.
+static int8_t attachedPin[8] = { -1, -1, -1, -1, -1, -1, -1, -1 };
+
 static void attachMeters() {
-  for (int i = 0; i < meterCount && i < 8; i++) {
-    if (meters[i].pin > 0) {
+  for (int i = 0; i < 8; i++) {
+    int pin = (i < meterCount && meters[i].pin > 0) ? meters[i].pin : -1;
+
+    // Release the channel if it's no longer used or its pin changed.
+    if (attachedPin[i] != -1 && attachedPin[i] != pin) {
+      ledcDetachPin(attachedPin[i]);
+      pinMode(attachedPin[i], OUTPUT);
+      digitalWrite(attachedPin[i], LOW);  // drive freed pin low so the meter reads zero
+      Serial.printf("[PWM] detach ch%d pin%d\n", i, attachedPin[i]);
+      attachedPin[i] = -1;
+    }
+
+    if (pin > 0 && attachedPin[i] != pin) {
       ledcSetup(i, PWM_FREQ, PWM_RES);
-      ledcAttachPin(meters[i].pin, i);
-      Serial.printf("[PWM] attach ch%d pin%d\n", i, meters[i].pin);
+      ledcAttachPin(pin, i);
+      attachedPin[i] = pin;
+      Serial.printf("[PWM] attach ch%d pin%d\n", i, pin);
     }
   }
 }