Embedded Systems and Actuators
What this domain tests
Embedded Systems and Actuators tests how a microcontroller reads sensors, processes signals and drives actuators. Expect GPIO, ADC, PWM, serial buses, interrupts and motor selection, with a calculation.
Core rules and concepts
- A microcontroller integrates a CPU, memory and input/output peripherals on one chip; a microprocessor typically needs external memory and support chips.
- GPIO pins are digital inputs or outputs. ADC converts an analog voltage to a digital number. PWM approximates an analog output by switching rapidly.
- Common buses: UART for asynchronous point-to-point, I2C for short multi-device buses, SPI for high-speed synchronous links.
- Interrupts let a processor respond to events without polling; real-time systems must meet deadlines, not just be fast.
- Actuators include DC motors, servos, steppers and solenoids. A driver or H-bridge is needed because microcontroller pins cannot supply motor current.
- PWM duty cycle = on-time/period. Average voltage ≈ supply voltage × duty cycle.
Worked example
An 8-bit PWM channel has values 0–255 and a 5 V supply. A duty value of 64 gives duty cycle = 64/255 ≈ 0.251, or 25.1%. Average voltage ≈ 5 × 0.251 ≈ 1.25 V. The PWM frequency is separate: it sets how often the cycle repeats, while duty sets the fraction of on-time.
Traps that cost marks
Do not confuse duty cycle with frequency. Do not connect a motor directly to a GPIO pin. Do not forget a shared ground between driver and microcontroller. Do not use a servo as a continuous-rotation DC motor without checking its type.