Fix stepper pulse timing

Always honor minimum period on stepper pulse generation, and fix timing calculations

Signed-off-by: etagle <ejtagle@hotmail.com>

Marlin/src/HAL/HAL_AVR/HAL.h

   int freeMemory(void);
 }
 
-// eeprom
-//void eeprom_write_byte(unsigned char *pos, unsigned char value);
-//unsigned char eeprom_read_byte(unsigned char *pos);
-
 // timers
 #define HAL_TIMER_RATE          ((F_CPU) / 8)    // i.e., 2MHz or 2.5MHz
 
 #define TEMP_TIMER_NUM          0
 #define PULSE_TIMER_NUM         STEP_TIMER_NUM
 
-#define STEPPER_TIMER_RATE      HAL_TIMER_RATE
-#define HAL_TICKS_PER_US        ((STEPPER_TIMER_RATE) / 1000000) // Cannot be of type double
-#define STEPPER_TIMER_PRESCALE  8
-#define STEP_TIMER_MIN_INTERVAL 8 // minimum time in µs between stepper interrupts
-
 #define TEMP_TIMER_FREQUENCY    ((F_CPU) / 64.0 / 256.0)
 
-#define TIMER_OCR_1             OCR1A
-#define TIMER_COUNTER_1         TCNT1
-
-#define TIMER_OCR_0             OCR0A
-#define TIMER_COUNTER_0         TCNT0
+#define STEPPER_TIMER_RATE      HAL_TIMER_RATE
+#define STEPPER_TIMER_PRESCALE  8
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // Cannot be of type double
 
-#define PULSE_TIMER_PRESCALE    STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT()  SBI(TIMSK1, OCIE1A)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() CBI(TIMSK1, OCIE1A)
   }
 }
 
+#define TIMER_OCR_1             OCR1A
+#define TIMER_COUNTER_1         TCNT1
+
+#define TIMER_OCR_0             OCR0A
+#define TIMER_COUNTER_0         TCNT0
+
 #define _CAT(a, ...) a ## __VA_ARGS__
 #define HAL_timer_set_compare(timer, compare) (_CAT(TIMER_OCR_, timer) = compare)
 #define HAL_timer_restrain(timer, interval_ticks) NOLESS(_CAT(TIMER_OCR_, timer), _CAT(TIMER_COUNTER_, timer) + interval_ticks)

Marlin/src/HAL/HAL_DUE/HAL_timers_Due.h

 typedef uint32_t hal_timer_t;
 #define HAL_TIMER_TYPE_MAX 0xFFFFFFFF
 
+#define HAL_TIMER_RATE         ((F_CPU) / 2)    // frequency of timers peripherals
+
 #define STEP_TIMER_NUM 3  // index of timer to use for stepper
 #define TEMP_TIMER_NUM 4  // index of timer to use for temperature
+#define PULSE_TIMER_NUM STEP_TIMER_NUM
 #define TONE_TIMER_NUM 6  // index of timer to use for beeper tones
 
-#define HAL_TIMER_RATE         ((F_CPU) / 2)    // frequency of timers peripherals
+#define TEMP_TIMER_FREQUENCY   1000 // temperature interrupt frequency
 
 #define STEPPER_TIMER_RATE     HAL_TIMER_RATE   // frequency of stepper timer (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
-#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / HAL_TICKS_PER_US)
-#define STEP_TIMER_MIN_INTERVAL   8 // minimum time in µs between stepper interrupts
-
-#define TEMP_TIMER_FREQUENCY   1000 // temperature interrupt frequency
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
+#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / STEPPER_TIMER_TICKS_PER_US)
 
-#define PULSE_TIMER_NUM STEP_TIMER_NUM
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_enable_interrupt(STEP_TIMER_NUM)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT()  HAL_timer_disable_interrupt(STEP_TIMER_NUM)

Marlin/src/HAL/HAL_LPC1768/HAL_timers.h

 typedef uint32_t hal_timer_t;
 #define HAL_TIMER_TYPE_MAX 0xFFFFFFFF
 
+#define HAL_TIMER_RATE         ((SystemCoreClock) / 4)  // frequency of timers peripherals
+
 #define STEP_TIMER_NUM 0  // Timer Index for Stepper
 #define TEMP_TIMER_NUM 1  // Timer Index for Temperature
 #define PULSE_TIMER_NUM STEP_TIMER_NUM
 #define PWM_TIMER_NUM 3   // Timer Index for PWM
 
-#define HAL_TIMER_RATE         ((SystemCoreClock) / 4)  // frequency of timers peripherals
-#define STEPPER_TIMER_RATE     HAL_TIMER_RATE   // frequency of stepper timer (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
-#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / HAL_TICKS_PER_US)
-
-#define STEP_TIMER_MIN_INTERVAL   8 // minimum time in µs between stepper interrupts
-
 #define TEMP_TIMER_RATE        1000000
 #define TEMP_TIMER_FREQUENCY   1000 // temperature interrupt frequency
 
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
+#define STEPPER_TIMER_RATE     HAL_TIMER_RATE   // frequency of stepper timer (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
+#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / STEPPER_TIMER_TICKS_PER_US)
+
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_enable_interrupt(STEP_TIMER_NUM)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_disable_interrupt(STEP_TIMER_NUM)

Marlin/src/HAL/HAL_STM32F1/HAL_timers_Stm32f1.h

 typedef uint16_t hal_timer_t;
 #define HAL_TIMER_TYPE_MAX 0xFFFF
 
+#define HAL_TIMER_RATE         (F_CPU)  // frequency of timers peripherals
+
+#define STEP_TIMER_CHAN 1 // Channel of the timer to use for compare and interrupts
+#define TEMP_TIMER_CHAN 1 // Channel of the timer to use for compare and interrupts
+
 #if defined(MCU_STM32F103CB) || defined(MCU_STM32F103C8)
   #define STEP_TIMER_NUM 4 // For C8/CB boards, use timer 4
 #else
   #define STEP_TIMER_NUM 5 // for other boards, five is fine.
 #endif
-
-#define STEP_TIMER_CHAN 1 // Channel of the timer to use for compare and interrupts
 #define TEMP_TIMER_NUM 2  // index of timer to use for temperature
-#define TEMP_TIMER_CHAN 1 // Channel of the timer to use for compare and interrupts
 #define PULSE_TIMER_NUM STEP_TIMER_NUM
 
-timer_dev* get_timer_dev(int number);
-
-#define TIMER_DEV(num) get_timer_dev(num)
-
-#define STEP_TIMER_DEV TIMER_DEV(STEP_TIMER_NUM)
-#define TEMP_TIMER_DEV TIMER_DEV(TEMP_TIMER_NUM)
-
-//STM32_HAVE_TIMER(n);
+#define TEMP_TIMER_PRESCALE     1000 // prescaler for setting Temp timer, 72Khz
+#define TEMP_TIMER_FREQUENCY    1000 // temperature interrupt frequency
 
-#define HAL_TIMER_RATE         (F_CPU)  // frequency of timers peripherals
 #define STEPPER_TIMER_PRESCALE 18             // prescaler for setting stepper timer, 4Mhz
 #define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
-
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
 
-#define TEMP_TIMER_PRESCALE     1000 // prescaler for setting Temp timer, 72Khz
-#define TEMP_TIMER_FREQUENCY    1000 // temperature interrupt frequency
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
-#define STEP_TIMER_MIN_INTERVAL    8 // minimum time in µs between stepper interrupts
+timer_dev* get_timer_dev(int number);
+#define TIMER_DEV(num) get_timer_dev(num)
+#define STEP_TIMER_DEV TIMER_DEV(STEP_TIMER_NUM)
+#define TEMP_TIMER_DEV TIMER_DEV(TEMP_TIMER_NUM)
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() timer_enable_irq(STEP_TIMER_DEV, STEP_TIMER_CHAN)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() timer_disable_irq(STEP_TIMER_DEV, STEP_TIMER_CHAN)

Marlin/src/HAL/HAL_STM32F4/HAL_timers_STM32F4.h

 #define hal_timer_t uint32_t  // TODO: One is 16-bit, one 32-bit - does this need to be checked?
 #define HAL_TIMER_TYPE_MAX 0xFFFF
 
-#define STEP_TIMER_NUM 0  // index of timer to use for stepper
-#define TEMP_TIMER_NUM 1  // index of timer to use for temperature
-
 #define HAL_TIMER_RATE         (HAL_RCC_GetSysClockFreq() / 2)  // frequency of timer peripherals
-#define STEPPER_TIMER_PRESCALE 54            // was 40,prescaler for setting stepper timer, 2Mhz
-#define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
 
+#define STEP_TIMER_NUM 0  // index of timer to use for stepper
+#define TEMP_TIMER_NUM 1  // index of timer to use for temperature
 #define PULSE_TIMER_NUM STEP_TIMER_NUM
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
 
 #define TEMP_TIMER_PRESCALE     1000 // prescaler for setting Temp timer, 72Khz
 #define TEMP_TIMER_FREQUENCY    1000 // temperature interrupt frequency
 
-#define STEP_TIMER_MIN_INTERVAL    8 // minimum time in µs between stepper interrupts
+#define STEPPER_TIMER_PRESCALE 54 // was 40,prescaler for setting stepper timer, 2Mhz
+#define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
+
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_enable_interrupt(STEP_TIMER_NUM)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_disable_interrupt(STEP_TIMER_NUM)

Marlin/src/HAL/HAL_STM32F7/HAL_timers_STM32F7.h

 #define hal_timer_t uint32_t  // TODO: One is 16-bit, one 32-bit - does this need to be checked?
 #define HAL_TIMER_TYPE_MAX 0xFFFF
 
-#define STEP_TIMER_NUM 0  // index of timer to use for stepper
-#define TEMP_TIMER_NUM 1  // index of timer to use for temperature
-
 #define HAL_TIMER_RATE         (HAL_RCC_GetSysClockFreq() / 2)  // frequency of timer peripherals
-#define STEPPER_TIMER_PRESCALE 54            // was 40,prescaler for setting stepper timer, 2Mhz
-#define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
 
+#define STEP_TIMER_NUM 0  // index of timer to use for stepper
+#define TEMP_TIMER_NUM 1  // index of timer to use for temperature
 #define PULSE_TIMER_NUM STEP_TIMER_NUM
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
 
-#define TEMP_TIMER_PRESCALE     1000 // prescaler for setting Temp timer, 72Khz
 #define TEMP_TIMER_FREQUENCY    1000 // temperature interrupt frequency
+#define TEMP_TIMER_PRESCALE     1000 // prescaler for setting Temp timer, 72Khz
+
+#define STEPPER_TIMER_PRESCALE 54    // was 40,prescaler for setting stepper timer, 2Mhz
+#define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
 
-#define STEP_TIMER_MIN_INTERVAL    8 // minimum time in µs between stepper interrupts
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_enable_interrupt(STEP_TIMER_NUM)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_disable_interrupt(STEP_TIMER_NUM)

Marlin/src/HAL/HAL_TEENSY35_36/HAL_timers_Teensy.h

 typedef uint32_t hal_timer_t;
 #define HAL_TIMER_TYPE_MAX 0xFFFFFFFF
 
-#define STEP_TIMER_NUM 0
-#define TEMP_TIMER_NUM 1
-#define PULSE_TIMER_NUM STEP_TIMER_NUM
-
 #define FTM0_TIMER_PRESCALE 8
 #define FTM1_TIMER_PRESCALE 4
 #define FTM0_TIMER_PRESCALE_BITS 0b011
 #define FTM1_TIMER_RATE (F_BUS / FTM1_TIMER_PRESCALE) // 60MHz / 4 = 15MHz
 
 #define HAL_TIMER_RATE         (FTM0_TIMER_RATE)
-#define STEPPER_TIMER_RATE     HAL_TIMER_RATE
-#define HAL_TICKS_PER_US       ((STEPPER_TIMER_RATE) / 1000000)
-#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / HAL_TICKS_PER_US)
-#define STEP_TIMER_MIN_INTERVAL   8 // minimum time in µs between stepper interrupts
 
-#define TEMP_TIMER_FREQUENCY   1000
+#define STEP_TIMER_NUM 0
+#define TEMP_TIMER_NUM 1
+#define PULSE_TIMER_NUM STEP_TIMER_NUM
+
+#define TEMP_TIMER_FREQUENCY    1000
+
+#define STEPPER_TIMER_RATE     HAL_TIMER_RATE
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000)
+#define STEPPER_TIMER_PRESCALE (CYCLES_PER_MICROSECOND / STEPPER_TIMER_TICKS_PER_US)
 
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
+#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define ENABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_enable_interrupt(STEP_TIMER_NUM)
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() HAL_timer_disable_interrupt(STEP_TIMER_NUM)

Marlin/src/module/stepper.cpp

       #else
         1
       #endif
-      * (HAL_TICKS_PER_US)
+      * (STEPPER_TIMER_TICKS_PER_US)
     );
 
     /**
   // Just update the value we will get at the end of the loop
   step_events_completed += events_to_do;
 
-  #if MINIMUM_STEPPER_PULSE
-    // Get the timer count and estimate the end of the pulse
-    hal_timer_t pulse_end = HAL_timer_get_count(PULSE_TIMER_NUM) + hal_timer_t((HAL_TICKS_PER_US) * (MINIMUM_STEPPER_PULSE));
-  #endif
+  // Get the timer count and estimate the end of the pulse
+  hal_timer_t pulse_end = HAL_timer_get_count(PULSE_TIMER_NUM) + hal_timer_t(MIN_PULSE_TICKS);
+
+  const hal_timer_t added_step_ticks = ADDED_STEP_TICKS;
 
   // Take multiple steps per interrupt (For high speed moves)
   do {
     #if MINIMUM_STEPPER_PULSE
       // Just wait for the requested pulse duration
       while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
-      // Add to the value, the value needed for the pulse end and ensuring the maximum driver rate is enforced
-      pulse_end += hal_timer_t(MIN_STEPPER_PULSE_CYCLES) - hal_timer_t((HAL_TICKS_PER_US) * (MINIMUM_STEPPER_PULSE));
     #endif
 
+    // Add the delay needed to ensure the maximum driver rate is enforced
+    if (signed(added_step_ticks) > 0) pulse_end += hal_timer_t(added_step_ticks);
+
     // Pulse stop
     #if HAS_X_STEP
       PULSE_STOP(X);
     // Decrement the count of pending pulses to do
     --events_to_do;
 
-    #if MINIMUM_STEPPER_PULSE
-      // For minimum pulse time wait after stopping pulses also
-      if (events_to_do) {
-        // Just wait for the requested pulse duration
-        while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
+    // For minimum pulse time wait after stopping pulses also
+    if (events_to_do) {
+      // Just wait for the requested pulse duration
+      while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
+      #if MINIMUM_STEPPER_PULSE
         // Add to the value, the time that the pulse must be active (to be used on the next loop)
-        pulse_end += hal_timer_t((HAL_TICKS_PER_US) * (MINIMUM_STEPPER_PULSE));
-      }
-    #endif
+        pulse_end += hal_timer_t(MIN_PULSE_TICKS);
+      #endif
+    }
 
   } while (events_to_do);
 }
           REV_E_DIR(active_extruder);
       #endif
 
+    // Get the timer count and estimate the end of the pulse
+    hal_timer_t pulse_end = HAL_timer_get_count(PULSE_TIMER_NUM) + hal_timer_t(MIN_PULSE_TICKS);
+
+    const hal_timer_t added_step_ticks = ADDED_STEP_TICKS;
+
     // Step E stepper if we have steps
     while (LA_steps) {
 
-      #if MINIMUM_STEPPER_PULSE
-        hal_timer_t pulse_end = HAL_timer_get_count(PULSE_TIMER_NUM) + hal_timer_t((HAL_TICKS_PER_US) * (MINIMUM_STEPPER_PULSE));
-      #endif
-
+      // Set the STEP pulse ON
       #if ENABLED(MIXING_EXTRUDER)
         MIXING_STEPPERS_LOOP(j) {
           // Step mixing steppers (proportionally)
         E_STEP_WRITE(active_extruder, !INVERT_E_STEP_PIN);
       #endif
 
+      // Enforce a minimum duration for STEP pulse ON
       #if MINIMUM_STEPPER_PULSE
         // Just wait for the requested pulse duration
         while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
-        // Add to the value, the value needed for the pulse end and ensuring the maximum driver rate is enforced
-        pulse_end += hal_timer_t(MIN_STEPPER_PULSE_CYCLES) - hal_timer_t((HAL_TICKS_PER_US) * (MINIMUM_STEPPER_PULSE));
       #endif
 
+      // Add the delay needed to ensure the maximum driver rate is enforced
+      if (signed(added_step_ticks) > 0) pulse_end += hal_timer_t(added_step_ticks);
+
       LA_steps < 0 ? ++LA_steps : --LA_steps;
 
+      // Set the STEP pulse OFF
       #if ENABLED(MIXING_EXTRUDER)
         MIXING_STEPPERS_LOOP(j) {
           if (delta_error_m[j] >= 0) {
         E_STEP_WRITE(active_extruder, INVERT_E_STEP_PIN);
       #endif
 
-      #if MINIMUM_STEPPER_PULSE
-        // For minimum pulse time wait before looping
-        // Just wait for the requested pulse duration
-        if (LA_steps) while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
-      #endif
-
+      // For minimum pulse time wait before looping
+      // Just wait for the requested pulse duration
+      if (LA_steps) {
+        while (HAL_timer_get_count(PULSE_TIMER_NUM) < pulse_end) { /* nada */ }
+        #if MINIMUM_STEPPER_PULSE
+          // Add to the value, the time that the pulse must be active (to be used on the next loop)
+          pulse_end += hal_timer_t(MIN_PULSE_TICKS);
+        #endif
+      }
     } // LA_steps
 
     return interval;