Initial

.gitignore

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+# Compiled object files
+*.o
+*.hex
+
+# Executables
+*.exe
+*.out
+*.elf
+
+# Build directories
+build/
+bin/
+
+# IDE and editor files
+#.vscode/
+.idea/
+*.sublime-project
+*.sublime-workspace
+
+# Dependency directories
+lib/
+vendor/
+
+# Log files
+*.log
+
+# OS generated files
+.DS_Store
+Thumbs.db

.vscode/c_cpp_properties.json

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+{
+    "configurations": [
+        {
+            "name": "AVR",
+            "includePath": [
+                "${workspaceFolder}/**",
+                "/usr/avr/include"
+            ],
+            "defines": [],
+            "compilerPath": "/usr/bin/avr-gcc",
+            "cStandard": "c11",
+            "cppStandard": "c++17",
+            "intelliSenseMode": "gcc-x64",
+            "compilerArgs": [
+                "-mmcu=atmega328p",
+                "-Os",
+                "-Wall",
+                "-Wextra",
+                "-Wpedantic",
+                "-Werror"
+            ]
+        }
+    ],
+    "version": 4
+}

README.md

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+# AVR Playground
+
+[QEMU AVR Docs](https://www.qemu.org/docs/master/system/target-avr.html)
+
+```bash
+sudo dnf install avr-binutils avr-libc avr-gcc avr-gcc-c++ avrdude qemu-system-avr
+```

main.c

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+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <avr/sleep.h>
+#include <util/delay.h>
+
+#define BLINK_TIME 0.5  // 1 second
+
+ISR(TIMER1_OVF_vect) {
+    PORTB ^= _BV(PORTB5);                         // Toggle the LED
+    TCNT1 = 65535 - (F_CPU / 1024 * BLINK_TIME);  // Reset timer value
+}
+
+int main(void) {
+    // Set PORTB5 as output
+    DDRB |= _BV(DDB5);
+
+    // Initialize TIMER1 value
+    TCNT1 = 65535 - (F_CPU / 1024 * BLINK_TIME);
+
+    // Set the prescaler to 1024
+    TCCR1B |= _BV(CS10) | _BV(CS12);
+
+    // Enable TIMER1 overflow interrupt
+    TIMSK1 |= _BV(TOIE1);
+
+    // Enable global interrupts
+    // sei();
+
+    // Enable global interrupts with style
+    __asm__ __volatile__ ("sei");
+
+    while (1) {
+        // Keep in mind that the sleep mode depth will affect the wake up time
+        sleep_cpu();  // Deep sleep
+        // set_sleep_mode(SLEEP_MODE_IDLE); // Idle sleep
+        // sleep_mode(); // Sets the CPU to whatever mode was set
+    }
+}

makefile

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+# AVR-GCC compiler
+CC = avr-gcc
+
+# Programmer (change it according to your programmer)
+PROGRAMMER = usbasp
+
+# MCU
+MCU = atmega328p
+QEMU_MACHINE_NAME = uno
+
+# Compiler flags
+CFLAGS = -std=c2x -Wall -Wno-array-bounds -mmcu=$(MCU) -DF_CPU=16000000UL -O3
+
+# Source files
+SRCS = main.c
+
+# Object files
+OBJS = $(SRCS:.c=.o)
+
+# Target file
+TARGET = main
+
+# Default target
+all: $(TARGET).hex
+
+# Compile C files
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+# Link object files
+$(TARGET).elf: $(OBJS)
+	$(CC) $(CFLAGS) $(OBJS) -o $(TARGET).elf
+	avr-strip $(TARGET).elf
+
+# Convert ELF to HEX
+$(TARGET).hex: $(TARGET).elf
+	avr-objcopy -O ihex -R .eeprom $(TARGET).elf $(TARGET).hex
+
+# Flash the program
+flash: $(TARGET).hex
+	avrdude -p $(MCU) -c $(PROGRAMMER) -U flash:w:$(TARGET).hex
+
+# Run the program in QEMU
+qemu: $(TARGET).elf
+	qemu-system-avr -machine $(QEMU_MACHINE_NAME) -bios $(TARGET).elf
+
+# View the generated assembly
+asm: $(TARGET).hex
+	avr-objdump -S $(TARGET).elf
+
+.PHONY: serial
+serial:
+	picocom -b 9600 /dev/ttyUSB0
+
+.PHONY: check
+check:
+	avrdude -p $(MCU) -c $(PROGRAMMER)
+
+# Clean
+.PHONY: clean
+clean:
+	rm -f $(OBJS) $(TARGET).elf $(TARGET).hex
+
+size: main.hex
+	avr-size --mcu=atmega328p main.hex