• arduino-cli: Command Line Interface for Arduino
• ARM cross compiler: sudo apt install gcc-arm-none-eabi

Sample program

We want to create the most simple program which goal is to light on the built-in LED, located at port PB27 on the Arduino Due.

Arduino

void setup()
{
    pinMode(LED_BUILTIN, OUTPUT);
}
void loop()
{
	digitalWrite(LED_BUILTIN, HIGH);
}

Embedded C

int main()
{
    PIOB->PIO_PER = 1<<27;       /* Enable port PB27 */
    PIOB->PIO_OER = 1<<27;       /* Configure PB27 as output */
    PIOB->PIO_ODSR = 0xFFFFFFFF; /* Write 1 in all PORTB ports */
    return 0;
}

Codes and compilation

$ ls -lR
./led-arduino:
total 4
-rw-r--r-- 1 pascal pascal 104 mai    1 12:58 led-arduino.ino
./led-embedded:
total 4
-rw-r--r-- 1 pascal pascal 81 mai    1 13:00 led-embedded.ino
$ arduino-cli compile --fqbn arduino:sam:arduino_due_x --output-dir led-arduino led-arduino
$ arduino-cli compile --fqbn arduino:sam:arduino_due_x --output-dir led-embedded led-embedded

Binary comparison

The embedded C code is 5 times smaller than the Arduino one which is a bit “weird” as both codes do the same thing! Let’s find why by reversing binaries and analyzing assembly codes.

As I was teaching some embedded C basics, I was asked what are some benefits of embedded C over the classic Arduino language for an Arduino-based board. This article tries to see what we can do by reversing a really simple program compiled with both methods for the Arduino Uno.

Prerequisites

• arduino-cli: Command Line Interface for Arduino. You will need to install the AVR toolchain as well: arduino-cli core install arduino:avr
• AVR cross compiler: sudo apt install gcc-avr
• Optional: an Arduino simulator such as SimulIDE

Sample program