This is where your code first touches the real world. Every microcontroller talks to LEDs, buttons, and sensors through GPIO pins, and knowing how to configure them, from input and output modes to pull-up and pull-down resistors, is the starting point for almost every project.
Next you'll see how a chip reacts to events without constantly checking for them. Interrupts let hardware pause the main program, run a short handler, and carry on, which is far more efficient than polling. You'll also learn how timers count clock ticks to measure time, create non-blocking delays, and trigger interrupts at exact intervals.
Together these three ideas make firmware responsive and predictable. Once you've finished, move on to Communication Protocols to connect your microcontroller to sensors and other devices.
What general-purpose input/output pins are and how they are configured, including why pull-up and pull-down resistors are needed and how push-pull and open-drain outputs differ.
A clear introduction to the idea behind interrupts: how a running program can be paused by an event, handled, and resumed, and why this beats constantly checking for changes.
A hands-on look at hardware interrupts running on a Nucleo-64 board, showing how an external event triggers an interrupt handler in real firmware.
How hardware timers and prescalers work, then using them to measure execution time, write non-blocking code instead of delays, and trigger interrupts at set intervals.