Setup custom targets in the "src/CMakeListst.txt" file. These include, the elf, hex, bin and an upload target.

src/CMakeLists.txt

@@ -1,3 +1,41 @@
-add_executable(main
+add_executable(${PROJECT_NAME}
     main.c    
 )
+
+# Ensure the build rules are defined
+set_target_properties(${PROJECT_NAME} PROPERTIES SUFFIX ".elf")
+
+if(NOT TARGET size)
+# Set the size utility to display the size of the final binary
+add_custom_target(size ALL
+    COMMAND ${CMAKE_SIZE} --format=avr --mcu=${AVR_MCU} ${CMAKE_PROJECT_NAME}.elf
+    DEPENDS ${CMAKE_PROJECT_NAME}.elf
+)
+endif()
+
+
+if(NOT TARGET hex)
+# Define how to convert ELF to HEX
+add_custom_target(hex ALL
+    COMMAND ${CMAKE_OBJCOPY} -O ihex -R .eeprom ${CMAKE_PROJECT_NAME}.elf ${CMAKE_PROJECT_NAME}.hex
+    DEPENDS ${CMAKE_PROJECT_NAME}.elf
+)
+endif()
+
+
+if(NOT TARGET bin)
+# Define how to convert ELF to BIN
+add_custom_target(bin ALL
+    COMMAND ${CMAKE_OBJCOPY} -O binary -R .eeprom ${CMAKE_PROJECT_NAME}.elf ${CMAKE_PROJECT_NAME}.bin
+    DEPENDS ${CMAKE_PROJECT_NAME}.elf
+)
+endif()
+
+
+if(NOT TARGET upload)
+# Upload command (adjust according to your programmer)
+add_custom_target(upload ALL
+    COMMAND avrdude -c usbtiny -p ${AVR_MCU} -U flash:w:${CMAKE_PROJECT_NAME}.hex
+    DEPENDS hex
+)
+endif()

src/main.c

@@ -1,8 +1,61 @@
 #include "stdio.h"
 
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <avr/sleep.h>
+
+
+//#############################
+//Globals
+//#############################
+
+#define LED_PIN PB0
+
+
+//#############################
+//Prototypes
+//#############################
+
+void led_blink(void);
+
+
+
+//#############################
+//MAIN
+//#############################
+
 int main(int argc, char **argv)
 { 
-    printf("Hello!\n");
+    led_blink();
+     
+    while(1) {
+        led_blink();
+        _delay_ms(500);
+    }
+    
     return 0;
 }
 
+
+
+//#############################
+//FUNCTIONS
+//#############################
+
+/*
+ * Input: None
+ * Output: None
+ * Description: Toggles the pin for the LED indicator.
+ */
+void led_blink(void) {
+    //Set the DDR for output.
+    DDRC |= (1<<LED_PIN);
+
+    PORTC ^= (1<<LED_PIN);
+    _delay_ms(250);
+    PORTC ^= (1<<LED_PIN);
+    _delay_ms(250);
+    
+}
+