Add timer interrupt + PWM work

LED Blink Input Output/GPIO-notes-pins.md

@@ -29,7 +29,8 @@ Microcontroller pins are grouped as:
 
 - PC6 is RESET pin  
   → DO NOT USE as GPIO  
-  → can reset system  
+  → can reset system 
+  → can be used but condition is if reset is disabled.  
 
 - PD0 and PD1 are Serial pins (RX TX)  
   → used for USB upload and debugging  

PWM-generator/Makefile

@@ -0,0 +1,24 @@
+MCU = atmega328p
+F_CPU = 16000000UL
+CC = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-gcc
+OBJCOPY = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-objcopy
+AVRDUDE = ../avrdude
+AVRDUDE_PROGRAMMER = arduino
+AVRDUDE_PORT = COM8
+AVRDUDE_BAUD = 115200
+
+CFLAGS = -mmcu=$(MCU) -DF_CPU=$(F_CPU) -Os -Wall
+
+all: main.hex
+
+main.elf: main.c
+	$(CC) $(CFLAGS) main.c -o main.elf
+
+main.hex: main.elf
+	$(OBJCOPY) -O ihex -R .eeprom main.elf main.hex
+
+upload: main.hex
+	$(AVRDUDE) -c $(AVRDUDE_PROGRAMMER) -p $(MCU) -P $(AVRDUDE_PORT) -b $(AVRDUDE_BAUD) -D -U flash:w:main.hex:i
+
+clean:
+	rm -f main.elf main.hex

PWM-generator/main.c

@@ -0,0 +1,33 @@
+#include <avr/io.h>
+
+int main(void) {
+    // 1. Set PB1 (OC1A) as output
+    DDRB |= (1 << PB1);
+
+    // 2. Fast PWM mode (WGM13:0 = 14)
+    TCCR1A = (1 << COM1A1) | (1 << WGM11);
+    TCCR1B = (1 << WGM12) | (1 << WGM13);
+
+    // 3. Prescaler = 8 (start timer)
+    TCCR1B |= (1 << CS11);
+
+    // 4. Set TOP value (frequency)
+    ICR1 = 19999;   // ~50 Hz (good for visible LED dimming demo)
+
+    // 5. Initial duty cycle
+    OCR1A = 0;
+
+    while (1) {
+        // Increase brightness
+        for (uint16_t i = 0; i < 2000; i++) {
+            OCR1A = i * 10;   // increase duty
+            for (volatile uint32_t d = 0; d < 5000; d++); // small delay
+        }
+
+        // Decrease brightness
+        for (int16_t i = 2000; i > 0; i--) {
+            OCR1A = i * 10;
+            for (volatile uint32_t d = 0; d < 5000; d++);
+        }
+    }
+}

Readmore.md

@@ -0,0 +1,15 @@
+# Timer Interrupt (ATmega328P)
+
+## Goal
+Generated 1ms interrupt using Timer1
+
+## Key Registers
+- TCCR1B → mode + prescaler
+- OCR1A → compare value
+- TIMSK1 → enable interrupt
+
+## Logic
+Timer counts → match OCR1A → ISR runs → ms++
+
+## Result
+LED blink using ms counter (non-blocking)

Timer-Interrupt/Makefile

@@ -0,0 +1,24 @@
+MCU = atmega328p
+F_CPU = 16000000UL
+CC = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-gcc
+OBJCOPY = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-objcopy
+AVRDUDE = ../avrdude
+AVRDUDE_PROGRAMMER = arduino
+AVRDUDE_PORT = COM8
+AVRDUDE_BAUD = 115200
+
+CFLAGS = -mmcu=$(MCU) -DF_CPU=$(F_CPU) -Os -Wall
+
+all: main.hex
+
+main.elf: main.c
+	$(CC) $(CFLAGS) main.c -o main.elf
+
+main.hex: main.elf
+	$(OBJCOPY) -O ihex -R .eeprom main.elf main.hex
+
+upload: main.hex
+	$(AVRDUDE) -c $(AVRDUDE_PROGRAMMER) -p $(MCU) -P $(AVRDUDE_PORT) -b $(AVRDUDE_BAUD) -D -U flash:w:main.hex:i
+
+clean:
+	rm -f main.elf main.hex

Timer-Interrupt/main.c

@@ -0,0 +1,39 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <stdint.h>
+
+volatile uint32_t ms = 0;
+
+void timer1_init(void) {
+    TCCR1A = 0;
+    TCCR1B = 0;
+    TCNT1  = 0;
+
+    TCCR1B |= (1 << WGM12);
+    OCR1A = 249;
+    TIMSK1 |= (1 << OCIE1A);
+    TCCR1B |= (1 << CS11) | (1 << CS10);
+    sei();
+}
+
+ISR(TIMER1_COMPA_vect) {
+    ms++;
+}
+
+void delay_ms(uint32_t delay){
+    uint32_t start = ms;
+    while ((ms - start) < delay) {
+    }
+}
+
+int main(void) {
+    DDRC |= (1<<PC0);
+    timer1_init();
+
+    while(1) {
+        PORTC |= (1<<PC0);
+        delay_ms(500);
+        PORTC &= ~(1<<PC0);
+        delay_ms(500);
+    }
+}

interrupts/Makefile

@@ -1,10 +1,10 @@
 MCU = atmega328p
 F_CPU = 16000000UL
-CC = C:\Users\sharm\Desktop\our main folder\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-gcc
+CC = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-gcc
-OBJCOPY = C:\Users\sharm\Desktop\our main folder\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-objcopy
+OBJCOPY = C:\Users\sharm\Desktop\Embedded Programming\avrprojects\avr8-gnu-toolchain-win32_x86_64\bin\avr-objcopy
 AVRDUDE = ../avrdude
 AVRDUDE_PROGRAMMER = arduino
-AVRDUDE_PORT = COM10
+AVRDUDE_PORT = COM8
 AVRDUDE_BAUD = 115200
 
 CFLAGS = -mmcu=$(MCU) -DF_CPU=$(F_CPU) -Os -Wall

interrupts/main.c

@@ -8,8 +8,7 @@ timer1_init();
    // prescaler 8
   DDRD &= ~(1 << PD2);
   PORTD |= (1 << PD2);
-  EICRA &= ~(1<<ISC00);
+  EICRA &= ~((1 << ISC01) | (1 << ISC00));
-  EICRA |= (1<<ISC01);
   EIMSK |= (1<<INT0);
 
   sei();

interrupts/pin-interrupt-notes.md

@@ -54,7 +54,7 @@ Controls how external interrupts trigger.
 
 # Interrupt Trigger Modes (INT0)
 
-## 1. Low Level (00)
+## 1. Low Level (00) //holding button
 
     EICRA &= ~((1 << ISC01) | (1 << ISC00));
 
@@ -67,7 +67,7 @@ Bit calculation:
 
 ---
 
-## 2. Any Logical Change (01)
+## 2. Any Logical Change (01) 
 
     EICRA &= ~(1 << ISC01);
     EICRA |=  (1 << ISC00);