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Simulator

micro:bit simulator, running in this tab

Mokxi is a free BBC micro:bit simulator that runs in your browser, with nothing to install and no account needed. Mokxi models the BBC micro:bit V2 on our own Cortex-M4 core, running the nRF52833 at 64 MHz on its real register map, with the 5x5 LED matrix scanned the way the hardware scans it.

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micro:bit: blinklive0.000 s 0.00x
Click to open it in the editor
Real firmware, running right now on our own core. Click it to open the circuit in the editor.
What is modeled

The numbers, not the marketing

Taken from the board's own contract document and put in plain words.

The core
Cortex-M4 (ARMv7-M), no FPU, at 64 MHz, with the datasheet cycle count of every instruction.
Peripherals
GPIO on both ports with the real PIN_CNF and OUT registers, GPIOTE with its event, task and PORT channels, TIMER0 to TIMER2, RTC0 on the 32.768 kHz clock, and UARTE0 with EasyDMA wired to the serial monitor.
The board itself
Twenty-five LEDs on five rows and five columns, buttons A and B behind the board pull-ups, the speaker on P0.00, and rings 0, 1 and 2 on the edge connector for a breadboard.
What is not there
The radio, the accelerometer, the compass, the microphone and the touch logo, and the SAADC, PWM and PPI peripherals.
Go further

The full board page

Every peripheral area, every example and the wiring notes, in one place.

BBC micro:bit V2 simulatorBlink, a button and the serial monitor, running.

Questions

Which micro:bit does this simulate?

The V2, on the nRF52833. The V1 is a different chip and is not modeled.

Does it run MakeCode or MicroPython?

No. Those ship as .hex images built against the vendor stack. The firmware runtime here is ours, and it is Arduino-shaped: write the sketch in C++ and press Run.

Does it simulate the radio or the sensors?

No. There is no radio, no accelerometer, no compass and no microphone in the model.

Is it free?

Yes, with no card and no account needed to try it.

Try your own firmware on the micro:bit

What you build here runs on the board on your desk, unchanged. Nothing to install and no account needed.

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