🛠 Deux ports série : Serial (USB) et Serial1 (broches 0/1)

Objectives

Take advantage of one of the major benefits of the Nano Every over the classic Nano: two hardware UARTs accessible on the connector. Serial goes through the USB bridge module (PC monitor), while Serial1 corresponds to the ATmega4809's USART on pins 0 (RX) and 1 (TX) in TTL. We build a pass-through: everything arriving from one side is output on the other.

Hardware

• 1 × Arduino Nano Every
• 1 × TTL module: GPS, HC-05/HC-06 (via a 5 V→3.3 V adapter if necessary), secondary USB-TTL converter
• Connecting wires, micro-USB cable

Complete code

// Passe-plat USB <-> UART broches 0(RX)/1(TX)
// Garde le moniteur USB libre pour le debogage pendant qu'un
// module (GPS, BLE...) parle sur Serial1.
void setup {
  Serial.begin(115200);    // USB (module pont embarque)
  Serial1.begin(9600);     // USART materielle sur broches 0/1
  Serial.println(F("Passe-plat pret: PC <-> module"));
}

void loop {
  if (Serial.available)  Serial1.write(Serial.read);    // PC -> module
  if (Serial1.available) Serial.write(Serial1.read);    // module -> PC
}

Expected verification

Connect the module to 0/1 (module RX → pin 1, module TX → pin 0, powered at 5 V or 3.3 V depending on the module). Open the serial monitor at 115200: you see the module's frames scrolling by; what you type from the PC is sent to the module. The USB port remains usable for debugging in parallel — impossible on the classic Nano, which has only one UART.

Common errors

• Crossing the pins: the board's TX (pin 1) goes to the module's RX, and the board's RX (pin 0) goes to the module's TX; connecting straight-through means nothing passes.
• Forgetting the common ground between board and module: random characters.
• 5 V level on a 3.3 V module: the 4809 uses 5 V logic on these pins; a 3.3 V module may require a voltage divider on the line going to it.
• Two different baud rates: Serial at 115200 and Serial1 at 9600, each begin with its own baud rate.
• Uploading goes through the USB bridge, not through 0/1, but a chatty module connected to 0/1 can saturate your serial code: disconnect it if in doubt.
• The USB bridge module is not a second programmable MCU: do not attempt to reprogram it, as you risk breaking the USB path.