diff --git a/firmware/main.c b/firmware/main.c
index 209ceb5..56bbef5 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -42,16 +42,17 @@ const char help_03[] PROGMEM = "\tpower                      show power state\n"
 const char help_04[] PROGMEM = "\tpower on                   switch power on\n";
 const char help_05[] PROGMEM = "\tpower off                  switch power off\n";
 const char help_06[] PROGMEM = "\tfan                        show fan speed\n";
-const char help_07[] PROGMEM = "\tmode                       show current mode\n";
-const char help_08[] PROGMEM = "\tmode N                     select mode\n";
-const char help_09[] PROGMEM = "\tch X Y                     show channel [1-2].[1-5] brightness\n";
-const char help_10[] PROGMEM = "\tch X Y Z                   set channel [1-2].[1-5] brightness [0-255]\n";
-const char help_11[] PROGMEM = "\tir learn power             learn the IR command to power on/off\n";
-const char help_12[] PROGMEM = "\tir learn mode              learn the IR command to change between modes\n";
-const char help_13[] PROGMEM = "\tir learn brightness up     learn the IR command to increase brightness\n";
-const char help_14[] PROGMEM = "\tir learn brightness down   learn the IR command to decrease brightness\n";
-const char help_15[] PROGMEM = "\tir learn channel next      learn the IR command to select next channel\n";
-const char help_16[] PROGMEM = "\tir learn channel previous  learn the IR command to select previous channel\n";
+const char help_07[] PROGMEM = "\ttemp                       show temperature\n";
+const char help_08[] PROGMEM = "\tmode                       show current mode\n";
+const char help_09[] PROGMEM = "\tmode N                     select mode\n";
+const char help_10[] PROGMEM = "\tch X Y                     show channel [1-2].[1-5] brightness\n";
+const char help_11[] PROGMEM = "\tch X Y Z                   set channel [1-2].[1-5] brightness [0-255]\n";
+const char help_12[] PROGMEM = "\tir learn power             learn the IR command to power on/off\n";
+const char help_13[] PROGMEM = "\tir learn mode              learn the IR command to change between modes\n";
+const char help_14[] PROGMEM = "\tir learn brightness up     learn the IR command to increase brightness\n";
+const char help_15[] PROGMEM = "\tir learn brightness down   learn the IR command to decrease brightness\n";
+const char help_16[] PROGMEM = "\tir learn channel next      learn the IR command to select next channel\n";
+const char help_17[] PROGMEM = "\tir learn channel previous  learn the IR command to select previous channel\n";
 PGM_P const help_table[] PROGMEM = {
 	help_00,
 	help_01,
@@ -69,7 +70,8 @@ PGM_P const help_table[] PROGMEM = {
 	help_13,
 	help_14,
 	help_15,
-	help_16
+	help_16,
+	help_17
 };
 
 //volatile uint8_t* PORTS[CHANNELS_1+CHANNELS_2] = {&PORTC,&PORTC,&PORTC,&PORTC,&PORTC,&PORTD,&PORTD,&PORTD,&PORTD,&PORTD};
@@ -276,6 +278,18 @@ void ioinit(void)
 	TIFR0 = (1<<OCF0A); /* clear timer 0 compare interrupt flag */
 	TIMSK0 |= (1<<OCIE0A); /* enable timer 0 compare interrupt */
 
+	/* configure internal temperature sensor */
+	ADMUX |= (1<<REFS1)|(1<<REFS0); /* select internal 1.1V voltage reference */
+	/* select ADC8 internal temperature sensor */
+	ADMUX |= (1<<MUX3);
+	ADMUX &= ~((1<<MUX2)|(1<<MUX1)|(1<<MUX0));
+	ADCSRA |= (1<<ADEN); /* enable ADC */
+	ADCSRA |= ((1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0)); /* prescaler at 128 */
+	/* continuously do the conversion (then don't wait for ADCS to clear) */
+	//ADCSRB &= ~((1<<ADTS2)|(1<<ADTS1)|(1<<ADTS0)); /* free-running mode */
+	//ADCSRA |= (1<<ADATE); /* conversion can be triggered */
+	//ADCSRA |= (1<<ADSC); /* start analogue to digital conversion */
+	
 	/* use UART as terminal */
 	uart_init();
 	stdout = &uart_output;
@@ -332,7 +346,7 @@ int main(void)
 		PORTB |= (1<<nPS_ON);
 	}
 
-	PIND |= ~(1<<LED); /* switch on LED */
+	PORTD &= ~(1<<LED); /* switch on LED */
 	while (true) {
 		/* calculated PWM values (on/off times) */
 		while (channel_flag) {
@@ -347,7 +361,7 @@ int main(void)
 		}
 		/* handle UART input */
 		while (uart_flag) {
-			PIND &= (1<<LED); /* switch off LED */
+			PORTD |= (1<<LED); /* switch off LED */
 			/* echo back */
 			char c = 0;
 			while (command_i<input_i) {
@@ -368,7 +382,7 @@ int main(void)
 				input_i = command_i = 0; /* reset input buffer */
 			}
 			uart_flag = false;
-			PIND |= ~(1<<LED); /* switch on LED */
+			PORTD &= ~(1<<LED); /* switch on LED */
 		}
 		/* handle power state */
 		while (power_flag) {
@@ -394,7 +408,7 @@ int main(void)
 		}
 		/* handle IR input */
 		while (ir_flag) {
-			PIND &= (1<<LED); /* switch off LED */
+			PORTD |= (1<<LED); /* switch off LED */
 			time2nec(burst,pulse-1); /* convert raw time burst in NEC format */
 			struct nec ir_tmp = nec2data(burst,pulse-1); /* decode NEC burst */
 			if (ir_tmp.valid) {
@@ -423,7 +437,7 @@ int main(void)
 			}
 			pulse = 0; /* reset burst */
 			ir_flag = false;
-			PIND |= ~(1<<LED); /* switch on LED */
+			PORTD &= ~(1<<LED); /* switch on LED */
 		}
 	}
 	return 0;
@@ -478,6 +492,10 @@ void uart_action(char* str)
 		} else {
 			printf("fan is off (or not detected)\n");
 		}
+	} else if (0==strcmp(word,"temp")) {
+		ADCSRA |= (1<<ADSC); /* start analogue to digital conversion */
+		loop_until_bit_is_clear(ADCSRA,ADSC); /* wait until conversion is finished */
+		printf("temperature: %u°C\n",(uint16_t)((ADCW-T_OFFSET)*T_FACTOR));
 	} else if (0==strcmp(word,"mode")) {
 		word = strtok(NULL,delimiter);
 		if (!word) {
diff --git a/firmware/main.h b/firmware/main.h
index 1b74b7f..4d81cac 100644
--- a/firmware/main.h
+++ b/firmware/main.h
@@ -22,6 +22,8 @@
 #define FAN PC5 /* FAN output */
 #define PWR_OK PB1 /* ATX power OK */
 #define nPS_ON PB2 /* ATX power supply ON switch */
+#define T_OFFSET 320 /* measured temperature offset (see AVR122) */
+#define T_FACTOR 0.653 /* measured temperature factor (see AVR122) */
 
 /* channel definitions */
 //#define CHANNELS_1 5 /* the number of outputs (zo use) for channel 1 (up to 5) */