How can I run multiple loops at the same time with an Arduino?

Hello,

to run multiple loop at the same time, independently, you should ... NOT use a second loop !

The loop() function in the Arduino program skeleton is a sort of "fake"; as a matter of fact it is only a way to tell the CPU "do this sequence indefinitely", but it is not covering the loop following the concept for(..) { } as it is usually intended in C/C++ programming. So first of all forget this vision.

Another thing that is too frequently used but as a matter of fact is more a damage than an advantage is the Delay(). It is a function blocking the processor for a certain period, so it is not the worth to use it in your case, but I suggest to never use the Delay() in programs excluding when you are doing tests to see if a certain part works.

Instead you should use a counter. If you initialise a long int global variable you can read the time of the processor in every moment without stopping the execution of the entire program.

long timeCounter; // milliseconds counter
long timePassed; // The actual milliseconds time

// We need a "loop" doing event 1 every 10 ms, one doing event 2 every 5 ms
// and one doing event 3 every 25 ms
long delay1 = 10;    // ms for cycle of event 1
long delay2 = 5;     // ms for cycle of event 2
long delay3 = 25;    // ms for cycle of event 3

// Counters for the number of triggered events before the
// corresponding event starts
int countEvent1, countEvent2, countEvent3;

int TRIGGER = 5; // ms to trigger the milliseconds timer

int MAX1 = 2; // Number or triggered milliseconds to start event1
int MAX2 = 1; // Number or triggered milliseconds to start event2
int MAX3 = 5; // Number or triggered milliseconds to start event3

// Initialisation
setup {
     timeCounter = millis(); // read the actual internal time
     timePassed = 0; // we start with no time passed

     countEvent1 = 0;
     countEvent2 = 0;
     countEvent3 = 0;
}

// Infinite cycle
loop() {

     // Read the actual time
     timePassed = millis() - timeCounter;
     // The smallest unit of time that should trigger an event is for event 2 (5 ms)
     // so our trigger should count this smaller unit

     // Check if the time passed after last reading is the trigger time
     if(timePassed >= TRIGGER) {
          // It's time to manage the events
          if(++countEvent1 == MAX1){
               // Reset the trigger and start the event
               event1();
               countEvent1 = 0;
          } // Event 1 ???
          
          // It's time to manage the events
          if(++countEvent1 == MAX2){
               // Reset the trigger and start the event
               event2();
               countEvent2 = 0;
          } // Event2 ???

          // It's time to manage the events
          if(++countEvent3 == MAX3){
               // Reset the trigger and start the event
               event3();
               countEvent3 = 0;
          } // Event3 ???

     } // Trigger ??

} // LOOP

// ============ Event functions

event1() {
// Add the code for your event
}

event2() {
// Add the code for your event
}

event3() {
// Adde the code for your event
}

Hello,

to run multiple loop at the same time, independently, you should ... NOT use a second loop !

The loop() function in the Arduino program skeleton is a sort of "fake"; as a matter of fact it is only a way to tell the CPU "do this sequence indefinitely", but it is not covering the loop following the concept for(..) { } as it is usually intended in C/C++ programming. So first of all forget this vision.

Another thing that is too frequently used but as a matter of fact is more a damage than an advantage is the Delay(). It is a function blocking the processor for a certain period, so it is not the worth to use it in your case, but I suggest to never use the Delay() in programs excluding when you are doing tests to see if a certain part works.

Instead you should use a counter. If you initialise a long int global variable you can read the time of the processor in every moment without stopping the execution of the entire program.

long timeCounter; // milliseconds counter
long timePassed; // The actual milliseconds time

// We need a "loop" doing event 1 every 10 ms, one doing event 2 every 5 ms
// and one doing event 3 every 25 ms
long delay1 = 10;    // ms for cycle of event 1
long delay2 = 5;     // ms for cycle of event 2
long delay3 = 25;    // ms for cycle of event 3

// Counters for the number of triggered events before the
// corresponding event starts
int countEvent1, countEvent2, countEvent3;

int TRIGGER = 5; // ms to trigger the milliseconds timer

int MAX1 = 2; // Number or triggered milliseconds to start event1
int MAX2 = 1; // Number or triggered milliseconds to start event2
int MAX3 = 5; // Number or triggered milliseconds to start event3

// Initialisation
setup {
     timeCounter = millis(); // read the actual internal time
     timePassed = 0; // we start with no time passed

     countEvent1 = 0;
     countEvent2 = 0;
     countEvent3 = 0;
}

// Infinite cycle
loop() {

     // Read the actual time
     timePassed = millis() - timeCounter;
     // The smallest unit of time that should trigger an event is for event 2 (5 ms)
     // so our trigger should count this smaller unit

     // Check if the time passed after last reading is the trigger time
     if(timePassed >= TRIGGER) {
          // It's time to manage the events
          if(++countEvent1 == MAX1){
               // Reset the trigger and start the event
               event1();
               countEvent1 = 0;
          } // Event 1 ???
          
          // It's time to manage the events
          if(++countEvent1 == MAX2){
               // Reset the trigger and start the event
               event2();
               countEvent2 = 0;
          } // Event2 ???

          // It's time to manage the events
          if(++countEvent3 == MAX3){
               // Reset the trigger and start the event
               event3();
               countEvent3 = 0;
          } // Event3 ???

     } // Trigger ??

} // LOOP

// ============ Event functions

event1() {
// Add the code for your event
}

event2() {
// Add the code for your event
}

event3() {
// Adde the code for your event
}