diff --git a/include/zh_avr_ac_dimmer.h b/include/zh_avr_ac_dimmer.h
index fb5785d..8d87065 100644
--- a/include/zh_avr_ac_dimmer.h
+++ b/include/zh_avr_ac_dimmer.h
@@ -18,10 +18,39 @@
         .triac_port = 0}
 
 #ifdef __cplusplus
+
 extern "C"
 {
 #endif
 
+#define ZH_ZERO_CROSSING_ON                           \
+    if (_is_zero_crossing == false)                   \
+    {                                                 \
+        switch (_init_config.triac_port)              \
+        {                                             \
+        case AVR_PORTB:                               \
+            PORTB &= ~(1 << _init_config.triac_gpio); \
+            break;                                    \
+        case AVR_PORTC:                               \
+            PORTC &= ~(1 << _init_config.triac_gpio); \
+        case AVR_PORTD:                               \
+            PORTD &= ~(1 << _init_config.triac_gpio); \
+            break;                                    \
+        default:                                      \
+            break;                                    \
+        }                                             \
+        _is_zero_crossing = true;                     \
+        break;                                        \
+    }
+
+#define ZH_ZERO_CROSSING_OFF       \
+    if (_is_zero_crossing == true) \
+    {                              \
+        _is_zero_crossing = false; \
+        flag = true;               \
+    }                              \
+    break;
+
     typedef enum
     {
         ZH_50HZ = 1,
diff --git a/zh_avr_ac_dimmer.c b/zh_avr_ac_dimmer.c
index dff7925..9dfb15e 100644
--- a/zh_avr_ac_dimmer.c
+++ b/zh_avr_ac_dimmer.c
@@ -1,5 +1,5 @@
 #include "zh_avr_ac_dimmer.h"
-// https://avr-start.ru/?p=3983
+
 static zh_avr_ac_dimmer_init_config_t _init_config = {0};
 volatile static bool _is_dimmer_work = false;
 volatile static uint8_t _dimmer_value = 0;
@@ -55,32 +55,33 @@ void zh_avr_ac_dimmer_isr_handler(void)
     case AVR_PORTB:
         if ((PINB & (1 << _init_config.zero_cross_gpio)) == (1 << _init_config.zero_cross_gpio))
         {
-            PORTB &= ~(1 << _init_config.triac_gpio);
-            flag = true;
+            ZH_ZERO_CROSSING_ON;
+        }
+        if ((PINB & (1 << _init_config.zero_cross_gpio)) == 0)
+        {
+            ZH_ZERO_CROSSING_OFF;
         }
         break;
     case AVR_PORTC:
         if ((PINC & (1 << _init_config.zero_cross_gpio)) == (1 << _init_config.zero_cross_gpio))
         {
-            PORTC &= ~(1 << _init_config.triac_gpio);
-            flag = true;
+            ZH_ZERO_CROSSING_ON;
+        }
+        if ((PINC & (1 << _init_config.zero_cross_gpio)) == 0)
+        {
+            ZH_ZERO_CROSSING_OFF;
         }
         break;
     case AVR_PORTD:
-        if (((PIND & (1 << _init_config.zero_cross_gpio)) == (1 << _init_config.zero_cross_gpio)) && _is_zero_crossing == false)
+        if ((PIND & (1 << _init_config.zero_cross_gpio)) == (1 << _init_config.zero_cross_gpio))
         {
-            PORTD &= ~(1 << _init_config.triac_gpio);
-            // flag = true;
-            _is_zero_crossing = true;
+            ZH_ZERO_CROSSING_ON;
         }
-        if (((PIND & (1 << _init_config.zero_cross_gpio)) == 0) && _is_zero_crossing == true)
+        if ((PIND & (1 << _init_config.zero_cross_gpio)) == 0)
         {
-            // PORTD &= ~(1 << _init_config.triac_gpio);
-            _is_zero_crossing = false;
-            flag = true;
+            ZH_ZERO_CROSSING_OFF;
         }
         break;
-
     default:
         break;
     }
@@ -90,24 +91,17 @@ void zh_avr_ac_dimmer_isr_handler(void)
         {
             if (_dimmer_value == 100)
             {
-                // cli();
                 TIMSK0 &= ~(1 << OCIE0A);
-                // sei();
                 switch (_init_config.triac_port)
                 {
                 case AVR_PORTB:
                     PORTB |= (1 << _init_config.triac_gpio);
-                    // _delay_us(ZH_TRIAC_TIME);
-                    // PORTB &= ~(1 << _init_config.triac_gpio);
                     break;
                 case AVR_PORTC:
                     PORTC |= (1 << _init_config.triac_gpio);
-                    // _delay_us(ZH_TRIAC_TIME);
-                    // PORTC &= ~(1 << _init_config.triac_gpio);
+                    break;
                 case AVR_PORTD:
                     PORTD |= (1 << _init_config.triac_gpio);
-                    // _delay_us(10);
-                    // PORTD &= ~(1 << _init_config.triac_gpio);
                     break;
                 default:
                     break;
@@ -115,11 +109,9 @@ void zh_avr_ac_dimmer_isr_handler(void)
             }
             else
             {
-                // cli();
                 TCNT0 = 0;
                 TIFR0 = (1 << OCF0A);
                 TIMSK0 |= (1 << OCIE0A);
-                // sei();
             }
         }
     }
@@ -182,22 +174,23 @@ static void _zh_avr_ac_dimmer_gpio_init(void)
 
 static avr_err_t _zh_avr_ac_dimmer_timer_init(void)
 {
+    // Frequency calculator http://rcl-radio.ru/?p=111487.
     TCCR0A |= (1 << WGM01);
     switch (F_CPU)
     {
-    case 8000000:
+    case 8000000: // When operating from an internal RC generator, frequency deviation of up to 5% is possible.
         switch (_init_config.ac_dimmer_frequency)
         {
         case ZH_50HZ:
-            OCR0A = 94; // Check. 99
+            OCR0A = 94; // Timer tick every 0,00009524 sec.
             TCCR0B |= (1 << CS01);
             break;
-        case ZH_60HZ:
-            OCR0A = 82;
+        case ZH_60HZ: // Timer tick every 0,00007937 sec.
+            OCR0A = 78;
             TCCR0B |= (1 << CS01);
             break;
-        case ZH_400HZ:
-            OCR0A = 99;
+        case ZH_400HZ: // Timer tick every 0,0000119 sec.
+            OCR0A = 94;
             TCCR0B |= (1 << CS00);
             break;
         default:
@@ -207,15 +200,15 @@ static avr_err_t _zh_avr_ac_dimmer_timer_init(void)
     case 16000000:
         switch (_init_config.ac_dimmer_frequency)
         {
-        case ZH_50HZ:
+        case ZH_50HZ: // Timer tick every 0,0001 sec.
             OCR0A = 24;
             TCCR0B |= (1 << CS01) | (1 << CS00);
             break;
-        case ZH_60HZ:
+        case ZH_60HZ: // Timer tick every 0,00008333 sec.
             OCR0A = 165;
             TCCR0B |= (1 << CS01);
             break;
-        case ZH_400HZ:
+        case ZH_400HZ: // Timer tick every 0,0000125 sec.
             OCR0A = 24;
             TCCR0B |= (1 << CS01);
             break;
@@ -226,15 +219,15 @@ static avr_err_t _zh_avr_ac_dimmer_timer_init(void)
     case 20000000:
         switch (_init_config.ac_dimmer_frequency)
         {
-        case ZH_50HZ:
+        case ZH_50HZ: // Timer tick every 0,0001 sec.
             OCR0A = 249;
             TCCR0B |= (1 << CS01);
             break;
-        case ZH_60HZ:
+        case ZH_60HZ: // Timer tick every 0,00008333 sec.
             OCR0A = 207;
             TCCR0B |= (1 << CS01);
             break;
-        case ZH_400HZ:
+        case ZH_400HZ: // Timer tick every 0,0000125 sec.
             OCR0A = 249;
             TCCR0B |= (1 << CS00);
             break;
@@ -277,5 +270,4 @@ ISR(TIMER0_COMPA_vect)
         }
     }
     TIFR0 = (1 << OCF0A);
-    // ++_dimmer_count;
 }
\ No newline at end of file