ATmega328P Interrupts: Complete Guide to ISR, IVT, Volatile, and Event-Driven Programming

Описание: Links:
Exercises:
ATmega Sound: https://drive.google.com/drive/folder...

Resources:
Overview Interrupt Vector Table (IVT): https://drive.google.com/file/d/1dpLs...
Practical Examples:
Interrupt versus Polling: https://drive.google.com/drive/folder...
Interrupt Vector Table (IVT): https://drive.google.com/drive/folder...


This comprehensive tutorial covers everything you need to know about hardware interrupts in the #ATmega328P microcontroller. Starting with the fundamental concept of why interrupts are superior to polling, you will learn how to transform a CPU-blocking while loop that constantly checks timer values into an efficient event-driven program where the timer automatically triggers your code when a second has passed.
The video walks through implementing your first interrupt-driven LED blink program step by step, configuring Timer1 in CTC mode with a prescaler of 1024 and OCR1A set to 15624 to generate a precise one-second interval. You will learn how to write Interrupt Service Routines (ISR) using the ISR() macro, derive interrupt vector names from the datasheet (like TIMER1_COMPA_vect), and create ISR aliases when multiple interrupts should execute the same code. Special ISR types like BADISR_vect (catch-all for unconfigured interrupts) and EMPTY_INTERRUPT are also covered.
The tutorial explains the two-level interrupt activation system: local interrupts enabled through timer mask registers (TIMSK) and global interrupts controlled via sei() and cli() functions. A practical demonstration using objdump shows exactly how the Interrupt Vector Table (IVT) is laid out in program memory, with hardwired addresses that the CPU jumps to when events occur, including the important distinction between word addresses (in the datasheet) and byte addresses (in disassembly).
The critical volatile keyword is demonstrated with a working example showing how the compiler will optimize away variables modified only in ISRs unless marked volatile - a common source of bugs. External interrupts are covered in depth, including Pin Change Interrupts (PCINT) grouped into three banks, the PCMSK and PCICR registers, and how to determine which pin triggered an interrupt using XOR comparison. The dedicated INT0/INT1 pins with configurable edge detection (rising, falling, or any change) are also explained.
Advanced topics include interrupt priority (lower vector number = higher priority), nested interrupts using ISR_NOBLOCK, and the 4+3 clock cycle overhead when entering an ISR. The video concludes with best practices: keep ISRs short, never use delay functions inside them, and replace polling with additional interrupts whenever possible.

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Chapters:
0:00 Introduction
2:39 Polling versus Interrupts
4:18 Wait for Timer0
6:55 Practical Example: Implementing an Interrupt
15:03 Interrupt Subroutines (ISR)
18:56 How to activate Interrupts (sei/cli)?
21:57 The Interrupt Vector Table (IVT)
23:36 Practical Example: How does the Interrupt Vector Table (IVT) work?
29:48 Practical Example: What does the volatile keyword do?
34:25 Interrupt Sources
46:40 Priority of Interrupts
49:59 Nested Interrupts
51:28 Bad Coding Examples
53:21 Summary and What's next?