diff --git a/ex00/main.c b/ex00/main.c
index 65207e8..62d8906 100644
--- a/ex00/main.c
+++ b/ex00/main.c
@@ -9,10 +9,10 @@
 #define D4 PORTB4
 
 int main(void) {
-	DDRB |= _BV(D1);
+	DDRB |= _BV(D2);
 
 	while (true) {
-		PORTB ^= _BV(D1);
+		PORTB ^= _BV(D2);
 		delay_ms(500);
 	};
 }
diff --git a/ex01/main.c b/ex01/main.c
index f514ef9..23c01e3 100644
--- a/ex01/main.c
+++ b/ex01/main.c
@@ -20,14 +20,14 @@
 //
 // all these information are on page ~140
 void timer1_init(void) {
-	// Set PB2 (OC1B) as output
-	DDRB   |= _BV(PB2);
+	// Set PB1 (OC1A) as output
+	DDRB   |= _BV(PB1);
 
 	// CTC mode (WGM12 = 1)
 	TCCR1B |= _BV(WGM12);
 
 	// Toggle OC1B on compare match (COM1B0 = 1)
-	TCCR1A |= _BV(COM1B0);
+	TCCR1A |= _BV(COM1A0);
 
 	// Set compare values
 	OCR1A	= TIMER_FREQ / 2;
diff --git a/ex02/Makefile b/ex02/Makefile
new file mode 100644
index 0000000..d64d0a1
--- /dev/null
+++ b/ex02/Makefile
@@ -0,0 +1,43 @@
+# Makefile
+MCU=atmega328p
+F_CPU=16000000
+CC=avr-gcc
+OBJCOPY=avr-objcopy
+CFLAGS=-std=c99 -Wall -Wextra -g -Os -mmcu=$(MCU) -DF_CPU=$(F_CPU) -Iinclude
+TARGET=main
+SERIAL=-P /dev/ttyUSB0 -b 115200
+
+
+SRC_DIR=.
+OBJ_DIR=build
+
+SRC_FILES=main.c utils.c
+OBJ_FILES=$(patsubst %.c,%.o,$(SRC_FILES))
+
+SRC=$(addprefix $(SRC_DIR)/,$(SRC_FILES))
+OBJ=$(addprefix $(OBJ_DIR)/,$(OBJ_FILES))
+
+all: flash
+
+re: fclean all
+
+fclean: clean
+clean:
+	rm -rf $(OBJ_DIR)
+	rm -f $(TARGET).hex
+
+hex: $(TARGET).hex
+
+flash: hex
+	avrdude -p $(MCU) -c arduino -U flash:w:$(TARGET).hex:i $(SERIAL) 
+
+$(OBJ_DIR)/$(TARGET).bin: $(OBJ)
+	$(CC) $(CFLAGS) $(OBJ) -o $@
+
+$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c 
+	mkdir -p $(shell dirname $@)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+
+$(TARGET).hex: $(OBJ_DIR)/$(TARGET).bin
+	$(OBJCOPY) -j .text -j .data -O ihex $< $@
diff --git a/ex02/include/mystd.h b/ex02/include/mystd.h
new file mode 100644
index 0000000..5d880c5
--- /dev/null
+++ b/ex02/include/mystd.h
@@ -0,0 +1,15 @@
+#ifndef MYSTDINT_H
+#define MYSTDINT_H
+
+typedef unsigned int uint16_t;
+typedef signed int	 int16_t;
+
+typedef unsigned char uint8_t;
+typedef signed char	  int8_t;
+
+typedef uint8_t bool;
+
+#define true  (1)
+#define false (0)
+
+#endif /* MYSTDINT_H */
diff --git a/ex02/include/utils.h b/ex02/include/utils.h
new file mode 100644
index 0000000..a9ab05f
--- /dev/null
+++ b/ex02/include/utils.h
@@ -0,0 +1,8 @@
+#ifndef UTILS_H
+#define UTILS_H
+
+#include "mystd.h"
+
+void delay_ms(uint16_t count);
+
+#endif /* UTILS_H */
diff --git a/ex02/main.c b/ex02/main.c
new file mode 100644
index 0000000..0b12ad9
--- /dev/null
+++ b/ex02/main.c
@@ -0,0 +1,45 @@
+#include <avr/io.h>
+#include "mystd.h"
+#include "utils.h"
+
+#define D1		   PORTB0
+#define D2		   PORTB1
+#define D3		   PORTB2
+#define D4		   PORTB4
+
+#define PRESCALER  256
+#define TIMER_FREQ (F_CPU / PRESCALER)
+
+#define DUTY_CYCLE 1
+
+// the PWM is something that counts from 0 to TOP
+// when it reached the value i'll name TOGGLE, it'll set the OUTPUT high
+// when it reaches TOP it'll reset COUNTER and set OUTPUT to low
+//
+// this means we have a clock that reaches TOP every X
+// and during this, we can set TOGGLE such that we set OUTPUT high
+void timer1_init(void) {
+	// Set PB1 (OC1A) as output
+	DDRB   |= _BV(PB1);
+
+	// Non-inverting OC1B -> the OC1B is set to low on TOP reached
+	TCCR1A |= _BV(COM1A1);
+
+	// set to PWM-fast with ICR1 as TOP
+	TCCR1A |= _BV(WGM11);
+	TCCR1B |= _BV(WGM13) | _BV(WGM12);
+
+	// TOP => 1hz
+	ICR1	= TIMER_FREQ - 1;
+	// TOGGLE => 1/10th of ICR1
+	OCR1A	= ((TIMER_FREQ / 10) * DUTY_CYCLE);
+
+	// Start timer with prescaler 256 (CS12)
+	TCCR1B |= _BV(CS12);
+}
+
+int main(void) {
+	timer1_init();
+	while (1)
+		;
+}
diff --git a/ex02/utils.c b/ex02/utils.c
new file mode 100644
index 0000000..96efa11
--- /dev/null
+++ b/ex02/utils.c
@@ -0,0 +1,19 @@
+#include "utils.h"
+
+// this just burns cycles.
+// the volatile is important, it means that the cpu can't optimize any
+// read/writes for the value
+static inline void spin_loop(volatile uint16_t counts) {
+	while (counts)
+		counts--;
+}
+
+void delay_ms(uint16_t ms) {
+	while (ms) {
+		// this value was taken using a delay of 500ms, and just recording the led
+		// blinking. it seems to be high enough such that each loop of delay_loop
+		// takes 1ms :D
+		spin_loop((F_CPU) / 5000);
+		ms--;
+	}
+}
diff --git a/ex03/Makefile b/ex03/Makefile
new file mode 100644
index 0000000..d64d0a1
--- /dev/null
+++ b/ex03/Makefile
@@ -0,0 +1,43 @@
+# Makefile
+MCU=atmega328p
+F_CPU=16000000
+CC=avr-gcc
+OBJCOPY=avr-objcopy
+CFLAGS=-std=c99 -Wall -Wextra -g -Os -mmcu=$(MCU) -DF_CPU=$(F_CPU) -Iinclude
+TARGET=main
+SERIAL=-P /dev/ttyUSB0 -b 115200
+
+
+SRC_DIR=.
+OBJ_DIR=build
+
+SRC_FILES=main.c utils.c
+OBJ_FILES=$(patsubst %.c,%.o,$(SRC_FILES))
+
+SRC=$(addprefix $(SRC_DIR)/,$(SRC_FILES))
+OBJ=$(addprefix $(OBJ_DIR)/,$(OBJ_FILES))
+
+all: flash
+
+re: fclean all
+
+fclean: clean
+clean:
+	rm -rf $(OBJ_DIR)
+	rm -f $(TARGET).hex
+
+hex: $(TARGET).hex
+
+flash: hex
+	avrdude -p $(MCU) -c arduino -U flash:w:$(TARGET).hex:i $(SERIAL) 
+
+$(OBJ_DIR)/$(TARGET).bin: $(OBJ)
+	$(CC) $(CFLAGS) $(OBJ) -o $@
+
+$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c 
+	mkdir -p $(shell dirname $@)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+
+$(TARGET).hex: $(OBJ_DIR)/$(TARGET).bin
+	$(OBJCOPY) -j .text -j .data -O ihex $< $@
diff --git a/ex03/include/mystd.h b/ex03/include/mystd.h
new file mode 100644
index 0000000..5d880c5
--- /dev/null
+++ b/ex03/include/mystd.h
@@ -0,0 +1,15 @@
+#ifndef MYSTDINT_H
+#define MYSTDINT_H
+
+typedef unsigned int uint16_t;
+typedef signed int	 int16_t;
+
+typedef unsigned char uint8_t;
+typedef signed char	  int8_t;
+
+typedef uint8_t bool;
+
+#define true  (1)
+#define false (0)
+
+#endif /* MYSTDINT_H */
diff --git a/ex03/include/utils.h b/ex03/include/utils.h
new file mode 100644
index 0000000..a9ab05f
--- /dev/null
+++ b/ex03/include/utils.h
@@ -0,0 +1,8 @@
+#ifndef UTILS_H
+#define UTILS_H
+
+#include "mystd.h"
+
+void delay_ms(uint16_t count);
+
+#endif /* UTILS_H */
diff --git a/ex03/main.c b/ex03/main.c
new file mode 100644
index 0000000..f2dc8aa
--- /dev/null
+++ b/ex03/main.c
@@ -0,0 +1,70 @@
+#include <avr/io.h>
+#include "mystd.h"
+#include "utils.h"
+
+#define D1		   PORTB0
+#define D2		   PORTB1
+#define D3		   PORTB2
+#define D4		   PORTB4
+
+#define PRESCALER  256
+#define TIMER_FREQ (F_CPU / PRESCALER)
+
+// the PWM is something that counts from 0 to TOP
+// when it reached the value i'll name TOGGLE, it'll set the OUTPUT high
+// when it reaches TOP it'll reset COUNTER and set OUTPUT to low
+//
+// this means we have a clock that reaches TOP every X
+// and during this, we can set TOGGLE such that we set OUTPUT high
+void timer1_init(uint8_t duty) {
+	// Set PB1 (OC1A) as output
+	DDRB   |= _BV(PB1);
+
+	// Non-inverting OC1B -> the OC1B is set to low on TOP reached
+	TCCR1A |= _BV(COM1A1);
+
+	// set to PWM-fast with ICR1 as TOP
+	TCCR1A |= _BV(WGM11);
+	TCCR1B |= _BV(WGM13) | _BV(WGM12);
+
+	// TOP => 1hz
+	ICR1	= TIMER_FREQ - 1;
+	// TOGGLE => 1/10th of ICR1
+	OCR1A	= ((TIMER_FREQ / 10) * duty);
+
+	// Start timer with prescaler 256 (CS12)
+	TCCR1B |= _BV(CS12);
+}
+
+#define SW1 PD2
+#define SW2 PD4
+
+int main(void) {
+	uint8_t prev	   = 0;
+	uint8_t duty_cycle = 1;
+	timer1_init(duty_cycle);
+	while (1) {
+		bool	has_changed = false;
+		// lets read both button in a single byte, and keep track of that too
+		uint8_t cur			= (PIND & (_BV(SW1) | _BV(SW2)));
+		// check for button SW1
+		if (prev & (_BV(SW1)) && !(cur & (_BV(SW1)))) {
+			duty_cycle++;
+			has_changed = true;
+		}
+		// check for button SW2
+		if (prev & (_BV(SW2)) && !(cur & (_BV(SW2)))) {
+			duty_cycle--;
+			has_changed = true;
+		}
+		prev = cur;
+		if (has_changed) {
+			if (duty_cycle > 10)
+				duty_cycle = 10;
+			if (duty_cycle < 1)
+				duty_cycle = 1;
+			timer1_init(duty_cycle);
+		}
+		delay_ms(10);
+	}
+}
diff --git a/ex03/utils.c b/ex03/utils.c
new file mode 100644
index 0000000..96efa11
--- /dev/null
+++ b/ex03/utils.c
@@ -0,0 +1,19 @@
+#include "utils.h"
+
+// this just burns cycles.
+// the volatile is important, it means that the cpu can't optimize any
+// read/writes for the value
+static inline void spin_loop(volatile uint16_t counts) {
+	while (counts)
+		counts--;
+}
+
+void delay_ms(uint16_t ms) {
+	while (ms) {
+		// this value was taken using a delay of 500ms, and just recording the led
+		// blinking. it seems to be high enough such that each loop of delay_loop
+		// takes 1ms :D
+		spin_loop((F_CPU) / 5000);
+		ms--;
+	}
+}