How can I run two loops at the same time? - c

Question

I have written code that makes LEDs blinks and moves a servo to several different directions. Here's the basic structure:
while(true){
//led on
//wait
//led off
//wait
}
while(true){
//servo to 45
//servo to 90
//servo to 270
}
I want both to run at the same time. The code above only turns on the LEDs, and infinitely since it's in the loop. The servo never works. I looked at other questions on here but I couldn't find anything relevant.
How can I make both the LEDs and servo work at the same time?

Answer 1

In general you cannot use two infinite loops. That's because it is senquentional program, so it cannot run second when until the first one is done. So if first loop is infinite, the second will never run.
To do some kind of 'multithreading', in simplest way is to use timers and interrupts.
In your case you want to run two different task. Blinking led and steering servos. When you use wait()/sleep()/delay(), the uC is simply stopping (except handling other things like interupts etc.). So you can set timers and in the interrupt blink led. Or better in the interrupt just set some flag, and in your main just check if flag has changed. Than just handle blink. So in general you will have in you main sth like this:
volatile uint8_t nowBlink = 0
ISR(TIMER1_OVF_vect)
{
// some timer handling and then:
nowBlink = 1
}
loop(){
if(nowBlink){
toggleLed();
nowBlink = 0;
}
setServo(123123);
}
Setting intterupt to 1 s, will blink your led with freq of 1 Hz, and then other parts of program will be done.
Here you have timers explained, and Here you have some libraries. Just read that and you should be master of arduino.
Best regards, voodoo16.

Answer 2

Don't use functions like delay_ms(), wait () etc. Try interrupt.
Use the struture like this :
int flag = 0;
void func_delay_50ms () interrupt
{
// set initial condition
flag ++;
}
void main
{
while (1)
{
if (flag == 4) // per 200ms
{
led = -led;
flag = 0;
}
if (!(flag % 2)) // per 100ms
{
servo ();
}
}
}
note : servo () should not block for a long time.
There are no really conturrent threads, And you should create an illusion to realize it.
(:з」∠) My poor English. pardon me.

Answer 3

Blinking a LED does not really require code on the MCU. You can use a timer and a PWM signal. https://www.arduino.cc/en/Tutorial/SecretsOfArduinoPWM

Answer 4

I wrote an Operating System for Arduino which supports multithreading in order to run multiple loops at once. Note that the servo has a range from 0-180. You can't turn in 270 degrees. You can find the source and further documentation here https://github.com/DrBubble/ArduinoOS.
This example code should do exactly what you want when running under the ArduinoOS.
#include "KernelInitializer.h"
#include "Servo.h"
#include "Led.h"
void setup()
{
KernelInitializer::InitializeKernel(mainThread);
}
void mainThread()
{
InitTask(secondThread);
while (true)
{
Led led(2); // replace 2 with the pin of your led
while (true)
{
led.TurnOn();
sleep(1000);
led.TurnOff();
sleep(1000);
}
}
}
void secondThread()
{
Servo servo(9); // replace 9 with the pin of your servo
while (true)
{
servo.SetValue(45);
sleep(1000);
servo.SetValue(90);
sleep(1000);
servo.SetValue(180);
sleep(1000);
}
}

Answer 5

You can simply use a goto statement
in both the loop.....you dont even need a loop if you use goto, like in assembly language.
c code for it is:
#include<stdio.h>
int main()
{
int count;
loop1:for(;;)
{
printf("Loop 1\n");
goto loop2;
}
loop2:for(;;)
{
printf("Loop 2\n");
goto loop1;
}
return 0;
}