Microbit V2 Firmware

This project is part of my personal journey into embedded systems development. It contains the source code for a bare-metal firmware for the BBC Microbit V2 (nRF52833), focused on learning low-level hardware abstraction and peripheral management.

Features

This firmware provides the following functionalities:

• Timer API: Hardware timer management supporting multiple channels (CC).
  • Simplified periodic task execution (Run/Stop/Init).
  • Interrupt-driven events for precise timing.
  • Auto-clear shortcuts for consistent frequency generation.
• UART API: Custom driver for serial communication.
  • Supports both polling and interrupt-driven transmission/reception.
• GPIO API: Direct register-level control for GPIO pins.
• GPIOTE API: Hardware-level bridge between GPIO pins and the event system.
  • Supports pin state change detection (rising, falling, or toggle) via hardware events.
  • Enables low-power wake-up and direct task triggering without CPU intervention.
• I2C API: Polling-based master driver for serial communication.
  • Supports read/write primitives with repeated start and hardware error detection.
• LSM303AGR Driver: Hardware abstraction for the 3-axis accelerometer and thermal sensor..
  • Features bit-field register mapping and LUT-based sensitivity scaling up to ±16g.
• Delay functions: for creating delays in the code.

Prerequisites

Installing PyOCD on Arch Linux

PyOCD is required for flashing and debugging the Microbit V2. Install it using yay:

# Install PyOCD from AUR
yay -S python-pyocd

# Verify installation
pyocd --version

# Install udev rules for USB access (no sudo needed for flashing)
sudo sh -c 'curl -o /etc/udev/rules.d/99-microbit.rules https://raw.githubusercontent.com/mbedmicro/pyOCD/master/udev/99-pyocd.rules'

# Reload udev rules
sudo udevadm control --reload-rules
sudo udevadm trigger

# Add your user to the plugdev group (logout/login required)
sudo usermod -a -G plugdev $USER

Usage

To compile this project, ensure you have the ARM GCC toolchain installed. Navigate to the project root directory and execute the following command:

make

This will generate the necessary .o files, link them, and produce the main.hex firmware image suitable for flashing onto the Microbit V2.

Other useful make commands:

• make clean: Removes all compiled object files (.o), executable files (.elf), binary files (.bin), map files (.map), and firmware images (.hex). Use this to clean up the build directory.
• make upload: This command is used to flash the compiled main.hex firmware onto a connected Microbit V2.

  make upload