diff --git a/firmware/main.c b/firmware/main.c
index d7c11b0..3cc9ab8 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -90,13 +90,14 @@ uint16_t burst[PULSE_MAX]; /* pulse times forming a burst (from timer) */
 
 /* channel variables */
 #define LEVELS 10 /* the number of PWM levels */
-volatile uint8_t ch_tick = 0; /* the tick counter for the channel PWM */
+volatile uint8_t ch_tick = 0; /* to tick for the channel PWM */
+uint8_t on[CHANNELS_1+CHANNELS_2]; /* at which tick turn the channel on */
+uint8_t off[CHANNELS_1+CHANNELS_2]; /* at which tick turn the channel off */
 
 /* flags, set in the interrupts and handled in the main program */
 volatile bool uart_flag = false; /* an incoming activity on the UART */
 volatile bool power_flag = false; /* a change in the power or fan */
 volatile bool ir_flag = false; /* to process a burst */
-volatile bool pwm_flag = false; /* to trigger a PWM tick */
 volatile bool channel_flag = false; /* indicate a change in the channel PWM values */
 volatile bool learn_flag = false; /* learn an IR command for an action */
 enum IR_ACTIONS to_learn = IR_ACTION_END; /* IR action to learn */
@@ -163,8 +164,23 @@ ISR(TIMER1_COMPA_vect) { /* timer 1 OCR1A match interrupt vector */
 
 /* timer 0 interrupt used generate a PWM for the channels */
 ISR(TIMER0_COMPA_vect) { /* timer 0 OCR0A match interrupt vector */
-	ch_tick = (ch_tick+1)%LEVELS;
-	pwm_flag = true;
+	ch_tick++;
+	if (pwr_ok) {
+		for (int i=0; i<CHANNELS_1+CHANNELS_2; i++) {
+			if (on[i]==ch_tick) {
+				if (on[i]!=off[i]) {
+					*(PORTS[i]) |= (1<<BITS[i]);
+				} else if (brightness[mode][i]==0) {
+					*(PORTS[i]) &= ~(1<<BITS[i]);
+				} else {
+					*(PORTS[i]) |= (1<<BITS[i]);
+				}
+			} else if (off[i]==ch_tick && brightness[mode][i]!=0xff) {
+				*(PORTS[i]) &= ~(1<<BITS[i]);
+			}
+		}
+		PIND = (1<<LED);
+	}
 }
 
 /* disable watched when booting */
@@ -245,7 +261,7 @@ void ioinit(void)
 	TCCR0B &= ~(1<<CS02);
 	TCCR0B |= (1<<CS01);
 	TCCR0B &= ~(1<<CS00);
-	OCR0A = 0xff; /* set PWM frequency (with prescale=8, 0x00=2304kHz-0xff=9kHz) */
+	OCR0A = 0x40; /* set PWM frequency (with prescale=8, 0x00=2304kHz-0xff=9kHz) */
 	TIFR0 = (1<<OCF0A); /* clear timer 0 compare interrupt flag */
 	TIMSK0 |= (1<<OCIE0A); /* enable timer 0 compare interrupt */
 
@@ -280,10 +296,6 @@ int main(void)
 	ir_data.command = 0;
 	uint8_t ir_repeat = 0; /* number of times the IR data has been repeated */
 
-	uint8_t on[CHANNELS_1+CHANNELS_2]; /* times when to switch on the output on the channels */
-	uint8_t off[CHANNELS_1+CHANNELS_2]; /* times when to switch off the output on the channels */
-	channel_flag = true; /* calculate above values later */
-
 	puts("LED dimmer up & running");
 
 	/* load (or initialize) settings */
@@ -299,6 +311,7 @@ int main(void)
 		load_settings();
 		puts("settings loaded");
 	}
+	channel_flag = true; /* calculate channel values later */
 	
 	/* switch power supply as saved */
 	if (power) {
@@ -312,32 +325,12 @@ int main(void)
 		while (channel_flag) {
 			uint8_t start = 0;
 			for (uint8_t i=0; i<CHANNELS_1+CHANNELS_2; i++) {
-				on[i] = (start)%LEVELS;
-				off[i] = (on[i]+brightness[mode][i])%LEVELS;
-				start = (start+brightness[mode][i])%LEVELS;
+				on[i] = start;
+				start += brightness[mode][i];
+				off[i] = start;
 			}
 			channel_flag = false;
 		}
-		/* generate PWM for channel */
-		while (pwm_flag) {
-			if (pwr_ok) {
-				for (int i=0; i<CHANNELS_1+CHANNELS_2; i++) {
-					if (on[i]==ch_tick) {
-						if (on[i]!=off[i]) {
-							*(PORTS[i]) |= (1<<BITS[i]);
-						} else if (brightness[mode][i]==0) {
-							*(PORTS[i]) &= ~(1<<BITS[i]);
-						} else {
-							*(PORTS[i]) |= (1<<BITS[i]);
-						}
-					} else if (off[i]==ch_tick) {
-						*(PORTS[i]) &= ~(1<<BITS[i]);
-					}
-				}
-				PIND |= (1<<LED);
-			}
-			pwm_flag = false;
-		}
 		/* handle UART input */
 		while (uart_flag) {
 			/* echo back */
@@ -553,6 +546,7 @@ void uart_action(char* str)
 				goto error;
 			}
 			brightness[mode][channel] = (uint8_t)br;
+			channel_flag = true;
 		}
 	} else {
 		goto error;