🛠 Faire clignoter la LED 13 d'une Duemilanove (et choisir le bon ATmega)

Objectives

Get started with the Arduino Duemilanove (2009), the last major "old-school" board before the Uno: an 8-bit AVR ATmega168 or ATmega328 running at 16 MHz, 5 V logic, FTDI FT232RL USB-to-serial bridge, and ATmegaBOOT bootloader. The first program is a classic — blinking the LED on pin 13 — but it hides THE historical pitfall of this board: there are two different chips behind the same board name, and you must select the correct one in the IDE.

Hardware

• 1 Arduino Duemilanove board with ATmega328 (or ATmega168 — check the silkscreen on the DIP-28 chip)
• 1 mini-USB cable (Duemilanove boards use a mini connector, not micro)
• PC: on Windows, install the FTDI VCP driver (modern Windows 10/11 drivers usually include it)
• Arduino IDE with the "Arduino AVR Boards" core

Full code

// Blink Duemilanove — LED integree broche 13 (HIGH = allumee)
const byte LED = 13;

void setup {
  pinMode(LED, OUTPUT);
}

void loop {
  digitalWrite(LED, HIGH);   // LED allumee
  delay(1000);
  digitalWrite(LED, LOW);    // LED eteinte
  delay(1000);
}

In the IDE: Tools > Board > Arduino Duemilanove or Diecimila, then Tools > Processor: select "ATmega328" if your chip is a 328 (or 328P), or "ATmega168" if it is a 168. Select the serial port (the FTDI USB-to-serial port, never a Bluetooth port) and Upload.

Expected verification

The "L" LED blinks once per second as soon as the upload finishes. The board's TX/RX LEDs blink during the upload (USB traffic via the FTDI chip). The program continues to run without USB, powered by a 7–12 V jack supply or a battery connected to the Vin/GND pins on the POWER connector.

Common errors

• Wrong processor selected: a sketch compiled for the 328 (57600 baud, 30720 bytes) uploaded to a 168 (19200 baud, 14336 bytes) fails with a bootloader timeout — and vice versa. This is THE Duemilanove pitfall: the board has the same name but there are two chips.
• Missing FTDI driver on Windows: no COM port appears; install the FTDI VCP driver (clones with counterfeit FT232R chips may refuse to enumerate after certain driver updates).
• Charge-only USB cable: the power LED lights up but no port appears.
• Confusing the power LED (ON, steady) with the user "L" LED (pin 13).
• Too weak a jack supply: below 7 V the 5 V rail becomes unstable, above 12 V the regulator overheats — the Duemilanove is strict about the recommended 7–12 V range.