Olimex STM32-H405 Blink
Olimex STM32-H405 Blink is a runnable microcontroller simulation example on SensBench — open the wired circuit, inspect the code, and compile real firmware in your browser, no install needed. Last updated Aug 14, 2026.
FREE SIMULATOR EXAMPLE · BEGINNER
Olimex STM32-H405 Blink
This example blinks the Olimex STM32-H405’s onboard PC12 status LED and prints a board banner to Serial — a quick bring-up check for the F405RG Cortex-M4 board. Active-HIGH logic, 250 ms rhythm, zero wiring.
| Board | Olimex STM32-H405 (STM32F405, Cortex-M4, 168 MHz) |
|---|---|
| Difficulty | beginner |
| Category | basics |
| Libraries | None — just the Arduino core |
| Runs in | Sensbench browser simulator — free, no account |
The exact circuit you get when you open this example — already wired, ready to run.
The sketch
// Olimex STM32-H405 (STM32F405RG) — onboard status LED on PC12 (active HIGH).
void setup() {
pinMode(PC12, OUTPUT);
Serial.begin(115200);
Serial.println("SENSBENCH Olimex H405");
}
void loop() {
digitalWrite(PC12, HIGH);
delay(250);
digitalWrite(PC12, LOW);
delay(250);
}How it works
pinMode(PC12, OUTPUT) configures the status LED pin, then the loop alternates HIGH (on) and LOW (off) at 250 ms — a 2 Hz blink. The active-HIGH wiring means the code reads exactly like Arduino convention.
The Serial.println() banner identifies the board at 115200 baud. Under QEMU the emulated STM32F405RG runs real Cortex-M4 instructions with FPU support at emulated clock rates, so the timing of this blink is faithful to silicon.
Before you build it for real
The H405’s PC12 status LED is active-HIGH — the opposite of the Blue Pill’s PC13, and a reminder that LED polarity is per-board. The F405 is a 3.3 V logic device despite its USB connector: the 5 V from USB powers the regulator, but the GPIOs are 3.3 V and not all pins are 5 V-tolerant. And on real hardware, the Olimex board’s boot configuration (BOOT0 strap) determines whether firmware starts — a detail the QEMU emulator always resolves in your favor.
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FAQ
What is special about the Olimex H405?
It is an STM32F405RG board from Olimex designed for embedded prototyping — compact, with the USB connector and status LED arranged for bench use. The F405 is a Cortex-M4 with FPU at 168 MHz, 1 MB flash and 192 KB RAM, so the board punches well above its size.
Is the PC12 LED active-HIGH?
Yes. The Olimex board drives its status LED from PC12 through a resistor to ground, so HIGH lights it and LOW turns it off — the Arduino-style polarity, different from the Blue Pill’s PC13 arrangement.