Aug 08 2016 Arduino Hello World without IDE

There is already a number of resources available about programming the Arduino with or without the IDE (I won't discuss here the pros and cons of using it). This aims at being a quick memo for those who already have some knowledge about C programming, and just want the minimal information required to compile C code and upload it to an Arduino board. This is basically a compilation of chunks of code retrieved here and there a couple of months ago and possibly updated.

Packages to install

To be able to compile and upload C code to an Arduino board, one has to install the following packages:

• avr-gcc : Cross Compiling GNU GCC targeted at avr
• avr-libc : C library for use with GCC on Atmel AVR microcontrollers
• avrdude : Software for programming Atmel AVR microcontroller

Note the avr-libc (and to some extend avr-gcc) install a lot of interesting libraries. Corresponding headers can be found in the following directory: /usr/avr/include/.

Makefile

The following Makefile summarizes the commands (with parameters) needed to compile a C project and upload it to an Arduino board:

baud=115200
avrType=atmega328p
avrFreq=16000000 # 16 Mhz
programmerDev=/dev/ttyUSB0
programmerType=arduino

cflags=-DF_CPU=$(avrFreq) -mmcu=$(avrType) -Wall -Werror -Wextra -Os
objects=$(patsubst %.c,%.o,$(wildcard *.c))

.PHONY: flash clean

all: main.hex

%.o: %.c
    avr-gcc $(cflags) -c $< -o $@

main.elf: $(objects)
    avr-gcc $(cflags) -o $@ $^

main.hex: main.elf
    avr-objcopy -j .text -j .data -O ihex $^ $@

flash: main.hex
    avrdude -p$(avrType) -c$(programmerType) -P$(programmerDev) -b$(baud) -v -U flash:w:$<

clean:
    rm -f main.hex main.elf $(objects)

To compile and upload a C project, one has to type the following commands (actually the last one is enough, since it will automatically build the main.hex file if required):

  $ make
  ...
  $ make flash
  ...

Depending on the board being used, one may have to tune the parameters at the beginning of the file. For instance, the avrType must reflect the type of AVR microcontroller on the board. The following header contains an extensive list of the supported hardware: /usr/avr/include/avr/io.h

Arduino Hello World

The minimal program on an Arduino consists in having a LED blink. I found this code somewhere (though I couldn't recover where from..):

#include <util/delay.h>
#include <avr/io.h>

#define LED PORTB5

int main(void) {
  DDRB |= (1 << LED);
  for/*ever*/(;;) {
    PORTB |= (1 << LED);
    _delay_ms(100);
    PORTB &= (0 << LED);
    _delay_ms(100);
  }
}

That's all folks. With the packages installed and the Makefile described earlier, one can compile this little C code and upload it to an Arduino board and see the little red LED blinking. From this starting point, one can easily work on bigger Arduino based projects.