ESP32: Count backwards asynchronously - c++

Question

I've written a little program which counts back from 5 to 0 and does a println afterwards. I've wrapped this a little bit, but please let me show my code:
Main.ino
#include "MyObject.h"
#include <string>
using namespace std;
MyObjekt *myObject;
void setup() {
Serial.begin(115200);
string trigger = "triggering";
myObject = new MyObject(trigger);
}
void loop(){}
MyObject.h
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <string>
using namespace std;
class MyObject{
public:
string field;
MyObject(string trigger);
string GetField(){ return field; }
void SetField(string trigger);
};
#endif
MyObject.cpp
#include "MyObject.h"
#include <string>
using namespace std;
#include "Timer.h"
MyObject::MyObject(string trigger){
SetField(trigger);
}
void MyObject::SetField(string trigger){
field = trigger;
auto f = []() {std::cout << "---------------- I waited to print! ----------------\n"; };
Timer t1{10000,f};
}
Timer.h
#include <iostream>
#include <chrono>
#include <thread>
#include <functional>
#include <mutex>
#include <condition_variable>
class Timer {
public:
Timer(size_t time, const std::function<void(void)>& f) : time{std::chrono::milliseconds{time}}, f{f} {}
~Timer() {wait_thread.join();}
private:
void wait_then_call()
{
std::unique_lock<std::mutex> lck{mtx};
for(int i{5}; i > 0; --i) {
//std::cout << "Thread " << wait_thread.get_id() << " countdown at: " << '\t' << i << '\n';
cv.wait_for(lck, time / 10);
}
f();
}
std::mutex mtx;
std::condition_variable cv{};
std::chrono::milliseconds time;
std::function <void(void)> f;
std::thread wait_thread{[this]() {wait_then_call();}};
};
Unfortately this blocks the main thread, so nothing other (like another println) is done during this. Is it somehow possible to do this countdown in the background and only do the println (f ) in the foreground (in other words: listening while doing work, if background-println is detected/sent to listener, execute, then listen again and continue with work)?
Would be really happy about every answer and help effort. Sorry if for my Problems expressing myself, i hope it became somehow clear what I am trying to achieve^^
Best regards

Answer 1

It looks like you're on Arduino. Using the arduino-timer library, the code should look something similar:
#include <arduino-timer.h>
const size_t TIMER_INTERVAL_MS = 1000;
volatile int counter = 5;
auto timer = timer_create_default();
void setup() {
timer.every(TIMER_INTERVAL_MS, [](void*) -> bool { counter--; return true; });
}
void loop() {
timer.tick();
if (counter <= 0) {
Serial.println("Counter is 0");
counter = 5; // Reset counter
}
Sorry, can't validate or run the code as I don't have an Arduino setup ready to go. But you should get the point.
You can also do more complex solutions like ask the timer peripheral for an interrupt; or set up timer service in the RTOS (assuming you've upgraded to one). The basic principle is the same.

Answer 2

First of all, don't use keyword new if you never call delete, as it would cause memory leak. What do you want can be achieved with two ways:
1. Use Counter
This is still run on the loopTask, but it is let other code to run.
long lastMillis = 0;
long interval = 1000;
long counter = 5;
void setup() {
Serial.begin(115200);
}
void loop() {
if (millis() - lastMillis > interval && counter >= 0) {
lastMillis = millis();
Serial.println(counter--);
}
//Other code would still run
}
2. Create Another Task
This would be completely asynchronous, even if you are calling delay() on the other task, the code on the loopTask would still run.
int counter = 5;
int interval = 1000;
void vTask(void *param) {
while (counter >= 0) {
delay(1000);
Serial.println(counter--);
}
vTaskDelete(NULL);
}
void setup() {
Serial.begin(115200);
xTaskCreate(vTask, "vTask", 4096, NULL, 1, NULL);
}
void loop() {}