Improve hardcoded bootloader code

Author: m3y54m

.clang-format

@@ -0,0 +1,20 @@
+# This .clang-format file is tailored for C projects following widely accepted best practices.
+# It enforces readability, consistency, and compatibility with most open source C codebases.
+BasedOnStyle: LLVM
+Language: C
+IndentWidth: 4
+TabWidth: 4
+UseTab: Never
+ColumnLimit: 80
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: InlineOnly
+BreakBeforeBraces: Allman
+SpaceBeforeParens: ControlStatements
+PointerAlignment: Left
+SortIncludes: true
+IncludeBlocks: Preserve
+IndentCaseLabels: true
+AlignConsecutiveAssignments: true
+AlignConsecutiveDeclarations: true
+AlignTrailingComments: true

.github/workflows/build.yml

@@ -43,5 +43,5 @@ jobs:
       with:
         name: bootloader
         path: |
-          build/bootloader/bootloader.bin
-          build/bootloader/bootloader.hex
+          build/bootloader_hardcoded/bootloader_hardcoded.bin
+          build/bootloader_hardcoded/bootloader_hardcoded.hex

CMakeLists.txt

@@ -1,4 +1,5 @@
 cmake_minimum_required(VERSION 3.10)
+
 # Use the AVR toolchain file (set before project())
 set(CMAKE_TOOLCHAIN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/toolchain.cmake CACHE STRING "AVR toolchain file")
 project("AVR Bootloader" C)
@@ -9,6 +10,7 @@ project("AVR Bootloader" C)
 
 # MCU and clock settings
 set(MCU atmega328p)
+
 # This definition is essential for libraries like <util/delay.h>
 set(F_CPU 16000000UL)
 
@@ -25,17 +27,18 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Os -mmcu=${MCU} -DF_CPU=${F_CPU}")
 
 # Add subprojects
 add_subdirectory(blinky)
-add_subdirectory(bootloader)
+add_subdirectory(bootloader_hardcoded)
 
 # Clean all build files and directories
-add_custom_target(clean_build
+add_custom_target(
+  clean_build
   COMMAND ${CMAKE_COMMAND} -E remove_directory "${CMAKE_BINARY_DIR}"
-  COMMENT "[[main]] Cleaning the entire build directory..."
+  COMMENT "[[${PROJECT_NAME}]] Cleaning the entire build directory..."
 )
 
 # Fully erase the flash and EEPROM (if present) of the microcontroller
 add_custom_target(
   erase_flash
   COMMAND avrdude -c ${AVRDUDE_PROGRAMMER} -p ${MCU} -e
-  COMMENT "[[main]] Erasing the flash and EEPROM of \"${MCU}\" using \"${AVRDUDE_PROGRAMMER}\""
+  COMMENT "[[${PROJECT_NAME}]] Erasing the flash and EEPROM of \"${MCU}\" using \"${AVRDUDE_PROGRAMMER}\""
 )

README.md

@@ -44,7 +44,6 @@ int main(void)
   while (1)
   {
     PORTB ^= (1 << PB5); // Toggle the LED
-
     _delay_ms(100); // Wait for 100 ms
   }
 

blinky/CMakeLists.txt

@@ -1,5 +1,8 @@
 cmake_minimum_required(VERSION 3.10)
-project(blinky C)
+
+# Dynamically set project name from directory name
+get_filename_component(PROJECT_NAME ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+project(${PROJECT_NAME} C)
 
 add_executable(${PROJECT_NAME}.elf src/main.c)
 

blinky/src/main.c

@@ -1,16 +1,18 @@
-
-// Blinky for AVR (ATmega328P)
-// Board connection:
-//   PB5 (Arduino Uno D13) ---> LED (with resistor)
-#define LED_PIN PB5
+/**
+ * @brief Blinky application for the ATmega328P.
+ * @details This application blinks an LED connected to pin PB5
+ * (Arduino Uno D13) at a 5Hz frequency.
+ */
 
 #include <stdint.h>
 #include <avr/io.h>
 #include <util/delay.h>
 
+#define LED_PIN PB5
+
 int main(void)
 {
-    // Set LED pin as output
+    // Configure LED pin as output
     DDRB |= (1U << LED_PIN);
 
     while (1)

bootloader/src/main.c

@@ -1,8 +1,25 @@
+
 cmake_minimum_required(VERSION 3.10)
-project(bootloader C)
+
+# Dynamically set project name from directory name
+get_filename_component(PROJECT_NAME ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+project(${PROJECT_NAME} C)
+
+# Set the start address for the bootloader (Boot Reset Vector) for ATmega328P
+# Fuse bits must be set accordingly to enable the bootloader section
+# BOOTSZ0 = 0, BOOTSZ1 = 1 for 1024 words (0x3C00 * 2 = 0x7800 for ATmega328P)
+set(BOOTLOADER_START_ADDRESS 0x7800)
+
+# Fuse bits for ATmega328P
+# Default values are set for a 16MHz external crystal with 1024 words bootloader size
+# CAUTION: Setting incorrect fuse bits can brick your microcontroller.
+# https://www.engbedded.com/fusecalc/
+set(LFUSE 0xFF)
+set(HFUSE 0xDA)
+set(EFUSE 0xFD)
 
 set(CMAKE_EXE_LINKER_FLAGS
-  "${CMAKE_EXE_LINKER_FLAGS} -Wl,-section-start=.text=0x7C00")
+  "${CMAKE_EXE_LINKER_FLAGS} -Wl,-section-start=.text=${BOOTLOADER_START_ADDRESS}")
 
 add_executable(${PROJECT_NAME}.elf src/main.c)
 
@@ -17,14 +34,6 @@ add_custom_target(
   COMMENT "[[${PROJECT_NAME}]] Building .hex and .bin files for \"${MCU}\""
 )
 
-# Fuse bits for ATmega328P
-# Default values are set for a 16MHz external crystal with 512 words bootloader size
-# CAUTION: Setting incorrect fuse bits can brick your microcontroller.
-# https://www.engbedded.com/fusecalc/
-set(LFUSE 0xFF CACHE STRING "Low fuse byte")
-set(HFUSE 0xDC CACHE STRING "High fuse byte")
-set(EFUSE 0xFD CACHE STRING "Extended fuse byte")
-
 # Write fuse bits
 add_custom_target(
   ${PROJECT_NAME}_write_fusebits
@@ -39,4 +48,5 @@ add_custom_target(
   COMMAND avrdude -c ${AVRDUDE_PROGRAMMER} -p ${MCU} -U flash:w:${PROJECT_NAME}.hex
   DEPENDS ${PROJECT_NAME}_build
   COMMENT "[[${PROJECT_NAME}]] Flashing the bootloader to \"${MCU}\" using \"${AVRDUDE_PROGRAMMER}\""
+  COMMENT "[[${PROJECT_NAME}]] Bootloader start address: 0x${BOOTLOADER_START_ADDRESS}"
 )