diff --git a/Marlin/src/HAL/AVR/Servo.cpp b/Marlin/src/HAL/AVR/Servo.cpp
index 526352b773..6dc1e2fb07 100644
--- a/Marlin/src/HAL/AVR/Servo.cpp
+++ b/Marlin/src/HAL/AVR/Servo.cpp
@@ -66,7 +66,7 @@ static volatile int8_t Channel[_Nbr_16timers];              // counter for the s
 
 /************ static functions common to all instances ***********************/
 
-static inline void handle_interrupts(timer16_Sequence_t timer, volatile uint16_t* TCNTn, volatile uint16_t* OCRnA) {
+static inline void handle_interrupts(const timer16_Sequence_t timer, volatile uint16_t* TCNTn, volatile uint16_t* OCRnA) {
   if (Channel[timer] < 0)
     *TCNTn = 0; // channel set to -1 indicated that refresh interval completed so reset the timer
   else {
diff --git a/Marlin/src/HAL/DUE/Servo.cpp b/Marlin/src/HAL/DUE/Servo.cpp
index 5524aa9cef..72a7d649ef 100644
--- a/Marlin/src/HAL/DUE/Servo.cpp
+++ b/Marlin/src/HAL/DUE/Servo.cpp
@@ -52,7 +52,7 @@ static volatile int8_t Channel[_Nbr_16timers];              // counter for the s
 // ------------------------
 /// Interrupt handler for the TC0 channel 1.
 // ------------------------
-void Servo_Handler(timer16_Sequence_t timer, Tc *pTc, uint8_t channel);
+void Servo_Handler(const timer16_Sequence_t, Tc*, const uint8_t);
 
 #ifdef _useTimer1
   void HANDLER_FOR_TIMER1() { Servo_Handler(_timer1, TC_FOR_TIMER1, CHANNEL_FOR_TIMER1); }
@@ -70,7 +70,7 @@ void Servo_Handler(timer16_Sequence_t timer, Tc *pTc, uint8_t channel);
   void HANDLER_FOR_TIMER5() { Servo_Handler(_timer5, TC_FOR_TIMER5, CHANNEL_FOR_TIMER5); }
 #endif
 
-void Servo_Handler(timer16_Sequence_t timer, Tc *tc, uint8_t channel) {
+void Servo_Handler(const timer16_Sequence_t timer, Tc *tc, const uint8_t channel) {
   // clear interrupt
   tc->TC_CHANNEL[channel].TC_SR;
   if (Channel[timer] < 0)
@@ -113,26 +113,21 @@ static void _initISR(Tc *tc, uint32_t channel, uint32_t id, IRQn_Type irqn) {
   TC_Start(tc, channel);
 }
 
-void initISR(timer16_Sequence_t timer) {
+void initISR(const timer16_Sequence_t timer) {
   #ifdef _useTimer1
-    if (timer == _timer1)
-      _initISR(TC_FOR_TIMER1, CHANNEL_FOR_TIMER1, ID_TC_FOR_TIMER1, IRQn_FOR_TIMER1);
+    if (timer == _timer1) _initISR(TC_FOR_TIMER1, CHANNEL_FOR_TIMER1, ID_TC_FOR_TIMER1, IRQn_FOR_TIMER1);
   #endif
   #ifdef _useTimer2
-    if (timer == _timer2)
-      _initISR(TC_FOR_TIMER2, CHANNEL_FOR_TIMER2, ID_TC_FOR_TIMER2, IRQn_FOR_TIMER2);
+    if (timer == _timer2) _initISR(TC_FOR_TIMER2, CHANNEL_FOR_TIMER2, ID_TC_FOR_TIMER2, IRQn_FOR_TIMER2);
   #endif
   #ifdef _useTimer3
-    if (timer == _timer3)
-      _initISR(TC_FOR_TIMER3, CHANNEL_FOR_TIMER3, ID_TC_FOR_TIMER3, IRQn_FOR_TIMER3);
+    if (timer == _timer3) _initISR(TC_FOR_TIMER3, CHANNEL_FOR_TIMER3, ID_TC_FOR_TIMER3, IRQn_FOR_TIMER3);
   #endif
   #ifdef _useTimer4
-    if (timer == _timer4)
-      _initISR(TC_FOR_TIMER4, CHANNEL_FOR_TIMER4, ID_TC_FOR_TIMER4, IRQn_FOR_TIMER4);
+    if (timer == _timer4) _initISR(TC_FOR_TIMER4, CHANNEL_FOR_TIMER4, ID_TC_FOR_TIMER4, IRQn_FOR_TIMER4);
   #endif
   #ifdef _useTimer5
-    if (timer == _timer5)
-      _initISR(TC_FOR_TIMER5, CHANNEL_FOR_TIMER5, ID_TC_FOR_TIMER5, IRQn_FOR_TIMER5);
+    if (timer == _timer5) _initISR(TC_FOR_TIMER5, CHANNEL_FOR_TIMER5, ID_TC_FOR_TIMER5, IRQn_FOR_TIMER5);
   #endif
 }
 
diff --git a/Marlin/src/HAL/SAMD51/Servo.cpp b/Marlin/src/HAL/SAMD51/Servo.cpp
index 23ab21c615..04461653f9 100644
--- a/Marlin/src/HAL/SAMD51/Servo.cpp
+++ b/Marlin/src/HAL/SAMD51/Servo.cpp
@@ -124,7 +124,7 @@ HAL_SERVO_TIMER_ISR() {
   }
 }
 
-void initISR(timer16_Sequence_t timer) {
+void initISR(const timer16_Sequence_t timer) {
   Tc * const tc = timer_config[SERVO_TC].pTc;
   const uint8_t tcChannel = TIMER_TCCHANNEL(timer);
 
@@ -201,7 +201,7 @@ void initISR(timer16_Sequence_t timer) {
   }
 }
 
-void finISR(timer16_Sequence_t timer) {
+void finISR(const timer16_Sequence_t timer) {
   Tc * const tc = timer_config[SERVO_TC].pTc;
   const uint8_t tcChannel = TIMER_TCCHANNEL(timer);
 
diff --git a/Marlin/src/HAL/STM32F1/Servo.cpp b/Marlin/src/HAL/STM32F1/Servo.cpp
index 8dc1ef7b6a..47ffb631cf 100644
--- a/Marlin/src/HAL/STM32F1/Servo.cpp
+++ b/Marlin/src/HAL/STM32F1/Servo.cpp
@@ -147,17 +147,17 @@ void libServo::move(const int32_t value) {
     uint16_t SR = timer_get_status(tdev);
     if (SR & TIMER_SR_CC1IF) { // channel 1 off
       #ifdef SERVO0_PWM_OD
-        OUT_WRITE_OD(SERVO0_PIN, 1); // off
+        OUT_WRITE_OD(SERVO0_PIN, HIGH); // off
       #else
-        OUT_WRITE(SERVO0_PIN, 0);
+        OUT_WRITE(SERVO0_PIN, LOW);
       #endif
       timer_reset_status_bit(tdev, TIMER_SR_CC1IF_BIT);
     }
     if (SR & TIMER_SR_CC2IF) { // channel 2 resume
       #ifdef SERVO0_PWM_OD
-        OUT_WRITE_OD(SERVO0_PIN, 0); // on
+        OUT_WRITE_OD(SERVO0_PIN, LOW); // on
       #else
-        OUT_WRITE(SERVO0_PIN, 1);
+        OUT_WRITE(SERVO0_PIN, HIGH);
       #endif
       timer_reset_status_bit(tdev, TIMER_SR_CC2IF_BIT);
     }
@@ -167,9 +167,9 @@ void libServo::move(const int32_t value) {
     timer_dev *tdev = HAL_get_timer_dev(MF_TIMER_SERVO0);
     if (!tdev) return false;
     #ifdef SERVO0_PWM_OD
-      OUT_WRITE_OD(inPin, 1);
+      OUT_WRITE_OD(inPin, HIGH);
     #else
-      OUT_WRITE(inPin, 0);
+      OUT_WRITE(inPin, LOW);
     #endif
 
     timer_pause(tdev);
@@ -200,9 +200,9 @@ void libServo::move(const int32_t value) {
       timer_disable_irq(tdev, 1);
       timer_disable_irq(tdev, 2);
       #ifdef SERVO0_PWM_OD
-        OUT_WRITE_OD(pin, 1); // off
+        OUT_WRITE_OD(pin, HIGH); // off
       #else
-        OUT_WRITE(pin, 0);
+        OUT_WRITE(pin, LOW);
       #endif
     }
   }
diff --git a/Marlin/src/HAL/shared/servo.cpp b/Marlin/src/HAL/shared/servo.cpp
index cfec6f3017..b838800de6 100644
--- a/Marlin/src/HAL/shared/servo.cpp
+++ b/Marlin/src/HAL/shared/servo.cpp
@@ -65,7 +65,7 @@ uint8_t ServoCount = 0;                         // the total number of attached
 
 /************ static functions common to all instances ***********************/
 
-static boolean isTimerActive(timer16_Sequence_t timer) {
+static bool anyTimerChannelActive(const timer16_Sequence_t timer) {
   // returns true if any servo is active on this timer
   LOOP_L_N(channel, SERVOS_PER_TIMER) {
     if (SERVO(timer, channel).Pin.isActive)
@@ -101,17 +101,18 @@ int8_t Servo::attach(const int inPin, const int inMin, const int inMax) {
   max = (MAX_PULSE_WIDTH - inMax) / 4;
 
   // initialize the timer if it has not already been initialized
-  timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);
-  if (!isTimerActive(timer)) initISR(timer);
-  servo_info[servoIndex].Pin.isActive = true;  // this must be set after the check for isTimerActive
+  const timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);
+  if (!anyTimerChannelActive(timer)) initISR(timer);
+  servo_info[servoIndex].Pin.isActive = true;  // this must be set after the check for anyTimerChannelActive
 
   return servoIndex;
 }
 
 void Servo::detach() {
   servo_info[servoIndex].Pin.isActive = false;
-  timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);
-  if (!isTimerActive(timer)) finISR(timer);
+  const timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);
+  if (!anyTimerChannelActive(timer)) finISR(timer);
+  //pinMode(servo_info[servoIndex].Pin.nbr, INPUT); // set servo pin to input
 }
 
 void Servo::write(int value) {
diff --git a/Marlin/src/HAL/shared/servo_private.h b/Marlin/src/HAL/shared/servo_private.h
index d85d8da8ba..021e0cb81d 100644
--- a/Marlin/src/HAL/shared/servo_private.h
+++ b/Marlin/src/HAL/shared/servo_private.h
@@ -70,10 +70,10 @@
 #define ticksToUs(_ticks) (unsigned(_ticks) * (SERVO_TIMER_PRESCALER) / clockCyclesPerMicrosecond())
 
 // convenience macros
-#define SERVO_INDEX_TO_TIMER(_servo_nbr) ((timer16_Sequence_t)(_servo_nbr / (SERVOS_PER_TIMER))) // returns the timer controlling this servo
-#define SERVO_INDEX_TO_CHANNEL(_servo_nbr) (_servo_nbr % (SERVOS_PER_TIMER))       // returns the index of the servo on this timer
-#define SERVO_INDEX(_timer,_channel)  ((_timer*(SERVOS_PER_TIMER)) + _channel)     // macro to access servo index by timer and channel
-#define SERVO(_timer,_channel)  (servo_info[SERVO_INDEX(_timer,_channel)])       // macro to access servo class by timer and channel
+#define SERVO_INDEX_TO_TIMER(_servo_nbr) timer16_Sequence_t(_servo_nbr / (SERVOS_PER_TIMER)) // the timer controlling this servo
+#define SERVO_INDEX_TO_CHANNEL(_servo_nbr) (_servo_nbr % (SERVOS_PER_TIMER))      // the index of the servo on this timer
+#define SERVO_INDEX(_timer,_channel)  ((_timer*(SERVOS_PER_TIMER)) + _channel)    // servo index by timer and channel
+#define SERVO(_timer,_channel)  servo_info[SERVO_INDEX(_timer,_channel)]          // servo class by timer and channel
 
 // Types
 
@@ -94,5 +94,5 @@ extern ServoInfo_t servo_info[MAX_SERVOS];
 
 // Public functions
 
-extern void initISR(timer16_Sequence_t timer);
-extern void finISR(timer16_Sequence_t timer);
+extern void initISR(const timer16_Sequence_t timer);
+extern void finISR(const timer16_Sequence_t timer);