Cross‑Compilation – Building for Embedded Targets

Cross‑compilation allows you to build a binary on a host machine for a different architecture (e.g., ARM Cortex‑M, AVR).

Typical toolchain prefix: arm-none-eabi- or avr-.

arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -O2 -c main.c -o main.o
arm-none-eabi-ld -T stm32.ld main.o -o firmware.elf
arm-none-eabi-objcopy -O binary firmware.elf firmware.bin

Key steps:

1. Select the right compiler (*-gcc).
2. Use a linker script (.ld) to place sections (.text, .data, .bss) at correct addresses.
3. Define the entry point (Reset_Handler).
4. Flash the binary using tools like openocd or vendor‑specific utilities.

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📚 Example: Minimal AVR Makefile

CC=avr-gcc
CFLAGS=-mmcu=atmega328p -Os -Wall
OBJ=main.o

all: main.hex

main.elf: $(OBJ)
	$(CC) $(CFLAGS) -o $@ $^

main.hex: main.elf
	avr-objcopy -O ihex -R .eeprom $< $@

clean:
	rm -f *.o *.elf *.hex