Ever wondered how your microcontroller knows how long to keep an LED on or how to blink it every second?
That’s the job of a timer.
Timers are the unsung heroes of embedded systems—they help us implement accurate delays, generate PWM signals, time events, and more. Today, we dig deep into:
🕒 Hardware Timers in Embedded Systems
🧠 What is a Timer?
A timer is a special peripheral that counts up (or down) at a known frequency. It’s driven by the MCU’s system clock and helps in measuring or generating time-based events.
Timers are essential for:
- Delays
- Pulse Width Modulation (PWM)
- Event Counting
- Timeouts
- Scheduling Tasks
🔁 Busy Wait vs Hardware Timer
🚫 Busy-Wait Delay (Not Recommended):
for (volatile int i = 0; i < 100000; i++);- CPU is stuck in the loop
- Not power-efficient
- No multitasking possible
✅ Hardware Timer Delay:
Use a hardware timer that runs independently of your code.
🔧 How a Basic Timer Works
Let’s say you have:
- System Clock = 16 MHz
- Prescaler = 64
- Timer counts: 16,000,000 / 64 = 250,000 ticks/sec
Now, to generate a 1 second delay, just wait until the timer reaches 250,000 counts.
🛠️ Register-Level Timer Example (STM32/AVR-style)
#define TIMER_COUNT (*((volatile uint32_t*)0x40038048))
#define TIMER_CONTROL (*((volatile uint32_t*)0x40038040))
void timer_init() {
TIMER_CONTROL = 0x01; // Enable timer, prescaler config
}
void delay_ms(uint32_t ms) {
uint32_t target = ms * 250; // Adjust based on clock/prescaler
TIMER_COUNT = 0; // Reset
while (TIMER_COUNT < target);
}Note: Addresses & values depend on your MCU. Always refer to the datasheet!
🧪 Example: Blinking an LED Every 1 Second Using a Timer
void led_blink_loop() {
while (1) {
toggle_led(); // Toggle GPIO
delay_ms(1000); // Wait 1 second
}
}💬 PWM with Timers
Timers can also generate PWM signals (used in motors, dimming LEDs, servos).
Key registers:
- Period Register → Total cycle time
- Duty Cycle Register → How long the signal is HIGH
// Pseudo-code for PWM
set_pwm_period(20000); // 20 ms period
set_pwm_duty_cycle(1500); // 1.5 ms high = center servo📘 Real-Life Timer Applications
| Application | Use of Timer |
| LED Blink | Fixed delay loop |
| Servo Motor | PWM signal generation |
| Debouncing Button | Software delay check |
| Real-Time Clock | Long-running timer |
| Sensor Polling | Timed intervals |
⚠️ Pro Tip
Always choose the right prescaler and timer width (8-bit, 16-bit, 32-bit) for your application. For long delays, either use:
- A larger timer (e.g., 32-bit)
- Cascaded timers
- External RTC
🔍 Up Next (Day 7):
📡 UART Basics – Serial Communication with Your Microcontroller
Learn how your microcontroller talks to your PC or other devices over serial (RS-232, USB-Serial).
