Summary - Embedded C++

Combine MMIO, free-standing and interrupts to write an LED blink app.

Summary - Embedded C++

In this group you saw the core embedded C++ tools: embedded system, MMIO, freestanding, interrupt and real-time. All ensure reliable operation on constrained hardware.

Now you will combine them in a volatile variable example. You will use volatile for shared variables and ISR-style flags together; this shows how embedded programs are built.

Volatile + flag

In an embedded program volatile variables both point to hardware registers and act as flags shared with the ISR. counter can be a counter, ready a flag; both must be volatile.

Example: volatile int counter = 0; volatile bool ready = false;. The assignment counter = 7; ready = true; signals that the ISR has finished and prepared data. The main loop checks ready and reads counter. Without volatile the compiler may do these accesses once and skip.

Exercise Write volatile counter + flag

Define global volatile int counter = 0; and volatile bool ready = false;. In main write counter = 7;, ready = true; and std::cout << counter + (ready ? 1 : 0);.

Show example solution

#include <iostream>

volatile int counter = 0;
volatile bool ready = false;

int main() {
    counter = 7;
    ready = true;
    std::cout << counter + (ready ? 1 : 0);
    return 0;
}

Test yourself

Which keyword is essential for MMIO?
```
volatile std::uint32_t* reg = ...;
```
- const
- inline
- static
- volatile
Show answer

volatile — volatile prevents the compiler from optimizing hardware access.

Complete the volatile pointer

volatile std::uint32_t* ____ = reinterpret_cast<volatile std::uint32_t*>(&storage);

Show answer

volatile std::uint32_t* reg = reinterpret_cast<volatile std::uint32_t*>(&storage);

Match each tool to its trait

embedded

Constrained resources
MMIO

Memory-mapped I/O
volatile

Hardware access
real-time

Fixed time

Next lesson: Compilation phases

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