diff --git a/.gitignore b/.gitignore
index 752b187..4bb05a4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,55 +1,2 @@
-### C ###
-# Prerequisites
-*.d
-
-# Object files
-*.o
-*.ko
-*.obj
-*.elf
-
-# Linker output
-*.ilk
-*.map
-*.exp
-
-# Precompiled Headers
-*.gch
-*.pch
-
-# Libraries
-*.lib
-*.a
-*.la
-*.lo
-
-# Shared objects (inc. Windows DLLs)
-*.dll
-*.so
-*.so.*
-*.dylib
-
-# Executables
-*.exe
-*.out
-*.app
-*.i*86
-*.x86_64
-*.hex
-
-# Debug files
-*.dSYM/
-*.su
-*.idb
-*.pdb
-
-# Kernel Module Compile Results
-*.mod*
-*.cmd
-.tmp_versions/
-modules.order
-Module.symvers
-Mkfile.old
-dkms.conf
-
-*.eep
+build/*
+obj/*
diff --git a/Makefile b/Makefile
index d07789f..907e8c6 100644
--- a/Makefile
+++ b/Makefile
@@ -2,12 +2,17 @@
 # is public domain), believed to be neutral to any flavor of "make"
 # (GNU make, BSD make, SysV make)
 
+SRC_DIR = src
+BUILD_DIR = build
+INC_DIR = include
+OBJ_DIR = obj
 
 MCU = atmega328p
 FORMAT = ihex
 TARGET = main
-SRC = $(TARGET).c
-ASRC =
+SRC = $(wildcard $(SRC_DIR)/*.c)
+OBJ = $(SRC:$(SRC_DIR)/%.c=$(OBJ_DIR)/%.o)
+LST = $(SRC:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.lst)
 OPT = s
 
 # Name of this Makefile (used for "make depend").
@@ -29,8 +34,7 @@ CSTANDARD = -std=gnu99
 CDEFS = -DF_CPU=1000000L -D__AVR__ -D__AVR_ATmega328P__
 
 # Place -I options here
-CINCS =
-
+CINCS = -I $(INC_DIR)
 
 CDEBUG = -g$(DEBUG)
 CWARN = -Wall -Wextra -Wstrict-prototypes
@@ -77,13 +81,12 @@ EXTMEMOPTS =
 #LDMAP = $(LDFLAGS) -Wl,-Map=$(TARGET).map,--cref
 LDFLAGS = $(EXTMEMOPTS) $(LDMAP) $(PRINTF_LIB) $(SCANF_LIB) $(MATH_LIB)
 
-
 # Programming support using avrdude. Settings and variables.
 
 AVRDUDE_PROGRAMMER = usbasp
 AVRDUDE_PORT = usb
 
-AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex
+AVRDUDE_WRITE_FLASH = -U flash:w:$(BUILD_DIR)/$(TARGET).hex
 #AVRDUDE_WRITE_EEPROM = -U eeprom:w:$(TARGET).eep
 
 
@@ -102,7 +105,8 @@ AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex
 #AVRDUDE_VERBOSE = -v -v
 
 AVRDUDE_BASIC = -p $(MCU) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER)
-AVRDUDE_FLAGS = $(AVRDUDE_BASIC) $(AVRDUDE_NO_VERIFY) $(AVRDUDE_VERBOSE) $(AVRDUDE_ERASE_COUNTER)
+AVRDUDE_FLAGS = $(AVRDUDE_BASIC) $(AVRDUDE_NO_VERIFY) $(AVRDUDE_VERBOSE) \
+				$(AVRDUDE_ERASE_COUNTER)
 
 
 CC = avr-gcc
@@ -111,101 +115,84 @@ OBJDUMP = avr-objdump
 SIZE = avr-size
 NM = avr-nm
 AVRDUDE = avrdude
-REMOVE = rm -f
+REMOVE = rm -rf
 MV = mv -f
 
-# Define all object files.
-OBJ = $(SRC:.c=.o) $(ASRC:.S=.o)
-
-# Define all listing files.
-LST = $(ASRC:.S=.lst) $(SRC:.c=.lst)
-
 # Combine all necessary flags and optional flags.
 # Add target processor to flags.
-ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS)
-ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)
+ALL_CFLAGS = -mmcu=$(MCU) $(CFLAGS)
 
 
 # Default target.
 all: build
 
-build: elf hex eep
+build: elf hex eep lss sym
 
-elf: $(TARGET).elf
-hex: $(TARGET).hex
-eep: $(TARGET).eep
-lss: $(TARGET).lss
-sym: $(TARGET).sym
+elf: $(BUILD_DIR)/$(TARGET).elf
+hex: $(BUILD_DIR)/$(TARGET).hex
+eep: $(BUILD_DIR)/$(TARGET).eep
+lss: $(BUILD_DIR)/$(TARGET).lss
+sym: $(BUILD_DIR)/$(TARGET).sym
 
 
 # Program the device.
-program: $(TARGET).hex $(TARGET).eep
+program: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep
 	$(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) $(AVRDUDE_WRITE_EEPROM)
 
 
 
 
 # Convert ELF to COFF for use in debugging / simulating in AVR Studio or VMLAB.
-COFFCONVERT=$(OBJCOPY) --debugging \
-			--change-section-address .data-0x800000 \
-			--change-section-address .bss-0x800000 \
-			--change-section-address .noinit-0x800000 \
-			--change-section-address .eeprom-0x810000
+COFFCONVERT = $(OBJCOPY) --debugging \
+			  --change-section-address .data-0x800000 \
+			  --change-section-address .bss-0x800000 \
+			  --change-section-address .noinit-0x800000 \
+			  --change-section-address .eeprom-0x810000
 
 
-coff: $(TARGET).elf
-	$(COFFCONVERT) -O coff-avr $(TARGET).elf $(TARGET).cof
+coff: $(BUILD_DIR)/$(TARGET).elf
+	$(COFFCONVERT) -O coff-avr $< $(TARGET).cof
 
 
-extcoff: $(TARGET).elf
-	$(COFFCONVERT) -O coff-ext-avr $(TARGET).elf $(TARGET).cof
+extcoff: $(BUILD_DIR)/$(TARGET).elf
+	$(COFFCONVERT) -O coff-ext-avr $< $(TARGET).cof
 
 
 .SUFFIXES: .elf .hex .eep .lss .sym
 
-.elf.hex:
+%.hex: %.elf
 	$(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@
 
-.elf.eep:
+%.eep: %.elf
 	-$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \
 		--change-section-lma .eeprom=0 -O $(FORMAT) $< $@
 
 # Create extended listing file from ELF output file.
-.elf.lss:
+%.lss: %.elf
 	$(OBJDUMP) -h -S $< > $@
 
 # Create a symbol table from ELF output file.
-.elf.sym:
+%.sym: %.elf
 	$(NM) -n $< > $@
 
 
 
 # Link: create ELF output file from object files.
-$(TARGET).elf: $(OBJ)
-	$(CC) $(ALL_CFLAGS) $(OBJ) --output $@ $(LDFLAGS)
+.SECONDARY: $(OBJ)
+$(BUILD_DIR)/%.elf: $(OBJ)
+	@mkdir -p $(@D)
+	$(CC) $(ALL_CFLAGS) $^ --output $@ $(LDFLAGS)
 
 
 # Compile: create object files from C source files.
-.c.o:
+$(OBJ_DIR)/%.o : $(SRC_DIR)/%.c
+	@mkdir -p $(@D)
 	$(CC) -c $(ALL_CFLAGS) $< -o $@
 
 
-# Compile: create assembler files from C source files.
-.c.s:
-	$(CC) -S $(ALL_CFLAGS) $< -o $@
-
-
-# Assemble: create object files from assembler source files.
-.S.o:
-	$(CC) -c $(ALL_ASFLAGS) $< -o $@
-
-
-
 # Target: clean project.
 clean:
-	$(REMOVE) $(TARGET).hex $(TARGET).eep $(TARGET).cof $(TARGET).elf \
-		$(TARGET).map $(TARGET).sym $(TARGET).lss \
-		$(OBJ) $(LST) $(SRC:.c=.s) $(SRC:.c=.d)
+	$(REMOVE) $(BUILD_DIR)/* $(OBJ_DIR)/*
 
 depend:
 	if grep '^# DO NOT DELETE' $(MAKEFILE) >/dev/null; \
@@ -216,6 +203,6 @@ depend:
 		fi
 	echo '# DO NOT DELETE THIS LINE -- make depend depends on it.' \
 		>> $(MAKEFILE); \
-		$(CC) -M -mmcu=$(MCU) $(CDEFS) $(CINCS) $(SRC) $(ASRC) >> $(MAKEFILE)
+		$(CC) -M -mmcu=$(MCU) $(CDEFS) $(CINCS) $(SRC) >> $(MAKEFILE)
 
 .PHONY:	all build elf hex eep lss sym program coff extcoff clean depend
diff --git a/io.h b/include/io.h
similarity index 50%
rename from io.h
rename to include/io.h
index a598778..013225e 100644
--- a/io.h
+++ b/include/io.h
@@ -1,10 +1,16 @@
 #ifndef PORTS_H
 #define PORTS_H
 
-#define LED_1 PD3
-#define SERVO_L PD5
+/* DS18B20+ is configured in DS18B20 library */
+
+/* Signal LED */
+#define LED_1 PD2
+
+/* Servo motors */
+#define SERVO_L PB1
 #define SERVO_R PD6
-#define TEMP PC0
+
+/* Photo sensors */
 #define PH_1 PC1
 #define PH_2 PC2
 #define PH_3 PC3
diff --git a/include/main.h b/include/main.h
new file mode 100644
index 0000000..7e52ff4
--- /dev/null
+++ b/include/main.h
@@ -0,0 +1,12 @@
+#ifndef MAIN_H
+#define MAIN_H
+
+typedef unsigned char byte;
+
+void initIO(void);
+void blinkLed(void);
+void readTemp(void);
+void readPhoto(void);
+void runServos(void);
+
+#endif
diff --git a/main.c b/main.c
index 65636cc..8919a74 100644
--- a/main.c
+++ b/main.c
@@ -1,32 +1,17 @@
 #include <avr/io.h>
+#include <avr/interrupt.h>
 #include <util/delay.h>
 #include "main.h"
 #include "io.h"
 
-#define LED_DELAY 100
-
-void blinkLed(void)
+void initIO()
 {
     DDRD |= (1 << LED_1);
-    while (1) {
-        PORTD |= (1 << LED_1);
-        _delay_ms(LED_DELAY);
-        PORTD &= ~(1 << LED_1);
-        _delay_ms(LED_DELAY);
-    }
-}
-
-void runServos(void)
-{
-    DDRD |= (1 << SERVO_L) | (1 << SERVO_R);
-    while (1) {
-        PORTD |= (1 << SERVO_L) | (1 << SERVO_R);
-    }
 }
 
 int main(void)
 {
-    blinkLed();
+    initIO();
 
     return 0;
 }
diff --git a/main.h b/main.h
deleted file mode 100644
index 354ca23..0000000
--- a/main.h
+++ /dev/null
@@ -1,25 +0,0 @@
-#ifndef MAIN_H
-#define MAIN_H
-
-#include <stdint.h>
-
-void blinkLed(void);
-void readTemp(void);
-void readPhoto(void);
-void runServos(void);
-/// Set pin value to high
-void setPinHigh(volatile uint8_t *port, int pin);
-/// Set pin value to low
-void setPinLow(volatile uint8_t *port, int pin);
-
-void setPinHigh(volatile uint8_t *port, int pin)
-{
-    *port |= (1 << pin);
-}
-
-void setPinLow(volatile uint8_t *port, int pin)
-{
-    *port &= ~(1 << pin);
-}
-
-#endif
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..fd3d5a1
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,49 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+/* https://davidegironi.blogspot.com/2014/09/a-ds18b20-1-wire-digital-thermometer.html */
+#include "ds18b20.h"
+/* https://github.com/kehribar/nrf24L01_plus */
+#include "main.h"
+#include "io.h"
+
+void initIO()
+{
+    DDRB |= (1 << SERVO_L);
+    TCCR1A |= (1 << COM1A1) | (1 << WGM10);
+    TCCR1B |= (1 << CS10) | (1 << WGM12);
+
+    DDRD |= (1 << SERVO_R);
+    TCCR0A |= (1 << COM0A1) | (1 << WGM00);
+    TCCR0B |= (1 << CS00) | (1 << WGM02);
+
+    DDRD |= (1 << LED_1);
+}
+
+void readTemp()
+{
+    double d;
+
+    sei();
+    for (;;) {
+        d = ds18b20_gettemp();
+        if (d >= 21)
+            PORTD |= (1 << LED_1);
+        else
+            PORTD &= ~(1 << LED_1);
+
+        _delay_ms(500);
+    }
+}
+
+int main(void)
+{
+    initIO();
+    readTemp();
+
+    /* Full speed */
+    OCR1A = 0x00;
+    OCR0A = 0x00;
+
+    return 0;
+}