🛠 Premiers pas sur le Teensy 4.1 : Teensyduino, Teensy Loader et premier Blink

Objectives

Discover PJRC's "Swiss Army knife" board: the Teensy 4.1 uses the NXP i.MX RT1062 (600 MHz Cortex-M7, officially overclockable to 912 MHz) from the Teensy 4.0 in a longer form factor that unlocks 55 I/O pins, Ethernet, native SDIO, and a second USB port. This tutorial covers the basics: installing Teensyduino, uploading a Blink sketch, and understanding the board's key peculiarity — there is no hardware reset button.

Hardware

• 1 Teensy 4.1 (manufactured by SparkFun since March 2025, sold with or without soldered headers) + a micro-USB data cable
• PC running Windows, Mac, or Linux with the Arduino IDE
• No wiring required: the orange LED on pin 13 is sufficient

Installation and Uploading

1. Install the official Teensy add-on via https://www.pjrc.com/teensy/td_download.html (supported alternatives: PlatformIO, Visual Micro, and the command-line Makefiles provided with the installer).
2. In the IDE: Tools > Board > Teensy > Teensy 4.1, then Tools > USB Type > Serial.
3. Click Upload: Teensy Loader launches automatically. If it does not detect the board, press the Program button once — this is NOT a reset button; it instructs the bootloader to enter USB programming mode.
4. The dedicated red LED indicates the bootloader status: dim = waiting, bright = flash writing in progress.

Key architectural point: the bootloader resides in a physically separate chip (a GD32E230F8 on boards manufactured after June 2022). The 8 MB of main flash is 100% yours, and a failed upload cannot brick it. If your code is truly unresponsive, holding the Program button for 13 to 17 seconds erases all non-volatile memory and restores the fallback program (LED blinking). If the Program button is inaccessible, plan for software recovery: the board has no reset pin; only software reset (watchdog or SCB_AIRCR register) is available.

Complete Code

void setup {
  Serial.begin(9600);      // série USB : le baud rate est ignoré
  pinMode(13, OUTPUT);     // LED orange — JAMAIS en INPUT_PULLUP :
                           // la LED de la broche fausse la lecture
}

void loop {
  digitalWrite(13, HIGH);
  delay(150);
  digitalWrite(13, LOW);
  delay(850);
}

Expected Verification

The orange LED blinks once per second upon power-up — your code executes immediately at power-up, with no bootloader delay. The Serial Monitor (USB Type = Serial) displays what you send to it; your program starts faster than the monitor opens, hence the classic while (!Serial && millis < 3000); to avoid missing any messages.

Common Errors

• Charge-only micro-USB cable: neither the Monitor nor the Loader sees the board — try another cable.
• Looking for the reset button: it does not exist. Unplug and replug USB or press Program to reprogram.
• Forgetting to change USB Type: a MIDI or Keyboard sketch uploaded with the default Serial type does nothing on the PC side.
• Powering via the 3.3 V pin: it is reserved for the output of the onboard regulator (250 mA max external); input is 5 V on VUSB/VIN — and since VUSB and VIN are connected, never power VIN while USB is plugged in.