Microcontrollers and Embedded Basics
This domain tests the block structure of a microcontroller, simple interfacing and the difference between a microcontroller and a general-purpose computer. Expect GPIO, resistor calculations and basic program flow.
Architecture and interfacing
A microcontroller contains a CPU, program memory (Flash/ROM), data memory (RAM), timers, serial ports, ADC and general-purpose input/output (GPIO). It runs one stored program repeatedly. GPIO pins can be inputs or outputs; an input needs a defined level, often by a pull-up resistor, and a mechanical button needs debouncing.
Worked example
An LED with a forward voltage of 2 V is driven from a 5 V GPIO pin at 10 mA. The series resistor is R = (5 − 2)/0.01 = 300 Ω. A 330 Ω standard value gives about 9.1 mA, which is safe. Connecting the LED directly to the pin would exceed the pin's current rating and could damage the microcontroller.
Program flow and peripherals
A typical program configures pins, reads inputs, makes decisions and writes outputs in a loop. PWM controls LED brightness or motor speed by varying duty cycle; the ADC converts an analog sensor voltage into a digital number. Interrupts let the CPU respond to events without constant polling.
Traps that cost marks
Omitting the current-limiting resistor; leaving a digital input floating; assuming all pins can source the same current; confusing program memory with data memory; forgetting that an 8-bit ADC returns 0–255, not volts.
Exam focus
Be ready to identify the function of each block, calculate an LED resistor, and explain why a pull-up or debounce circuit is needed.