Summary - Embedded C++
- C++ course
- Expert
- Lesson 36/47
- 5 min
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.
Practice 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);.
Starter code
#include <iostream>
// Define the counter and ready volatile variables here
int main() {
// Set counter to 7, ready to true and print the total
return 0;
}Sample 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;
}Expected output
8
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which keyword is essential for MMIO?
volatile std::uint32_t* reg = ...;- const
- inline
- static
- volatile Correct answer
Explanation: volatile prevents the compiler from optimizing hardware access.
2 Complete the volatile pointer
volatile std::uint32_t* ____ = reinterpret_cast<volatile std::uint32_t*>(&storage);volatile std::uint32_t* reg = reinterpret_cast<volatile std::uint32_t*>(&storage);Explanation: Write volatile std::uint32_t* reg = ...;; reg points to storage.
3 Match each tool to its trait
| Term | Meaning |
|---|---|
embedded |
Constrained resources |
MMIO |
Memory-mapped I/O |
volatile |
Hardware access |
real-time |
Fixed time |