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Multiple Arduino functions without delay

Former Member

I have literally zero coding experience but have run into the need for it at my job -- all help appreciated. Basically, I am trying to accomplish many things at once and am not sure how to translate what i need into code. What I need: a tone and a light to simultaneously flash on for 500 milliseconds and then off again for 6 seconds; water reward to be delivered (by turning on/ off a solenoid) 2 seconds after the tone/LED have turned off, with the solenoid being open for 25 milliseconds; continuous collection of data from an input potentiometer. Since i need to monitor the input from the potentiometer at all times, i cannot use "delay()" because i cannot have the board stop reading the values from the potentiometer to preform a function.

 

This is a code i attempted -- however, the issue is the timing for the LED/tone and the solenoid. I need the solenoid to always open 2 seconds after the LED/tone turn off and it needs to open for 25 milliseconds and then shut back off. i have put hours into trying to figure out a way to do this --- as the code is now, the led/tone turn on and off fine, but the solenoid has a longer delay time (because i was trying to get it to come 2 seconds after the led/tone went off) and the excess time builds onto itself and makes the timing of the solenoid vary in its proximity to the LED/tone.

 

#include <elapsedMillis.h> //the timer.

 

 

//stopwatches

elapsedMillis timer; 

 

 

int ledPin = 11;

int lick = 4;

int solenoid = 8;

int speaker = 2;

int ledOn = 500;       //milliseconds

int ledOff = 6000;

int solenoidOn = 25;

int solenoidOff = 8475;

int LickState;

 

 

int playTime = 500;  //how long speakers will play for

int freq = 8000;  //frequency for left prize speakers in hz

int toneTime = 500;

 

 

unsigned long lms;        //time from millis()

unsigned long lmsLast;    //last time the LED changed state

unsigned long sms;        //time from millis()

unsigned long smsLast;

unsigned int LedOn = 0;

unsigned int Reward = 0;

unsigned int Lick = 0;

boolean ledState;        //current LED state

boolean solenoidState;

 

 

void setup(void){

  Serial.begin(9600);

  pinMode(lick, INPUT); 

  pinMode(ledPin, OUTPUT);

  pinMode(solenoid, OUTPUT);

  pinMode(speaker, OUTPUT);

 

 

  elapsedMillis timer = 0;

}

 

 

void loop(void){

  int ledState = digitalRead(ledPin);

  int lickstate = digitalRead(lick);

  if (lickstate == HIGH){

//    Serial.println(lickstate);

    Serial.println(timer); }

  lms = millis();

    blinkLED();

  sms = millis();

    blinkLED();

   

 

} }

 

 

void blinkLED(void){

 

 

    if (lms - lmsLast > (ledState ? ledOn : ledOff)) {

        digitalWrite(ledPin, ledState = !ledState);

        lmsLast = lms;

        tone (speaker, freq, toneTime);

        Serial.print("Led");

        Serial.println(timer);

    }

    if (sms - smsLast > (solenoidState ? solenoidOn : solenoidOff)) {

        digitalWrite(solenoid, solenoidState = !solenoidState);

        smsLast = sms;

        Serial.print("Reward");

        Serial.println(timer);

    }

}

 

I have tried using if then statements to say that if the LED state is HIGH, then wait 2 seconds and deliver the reward --- the issue is the "wait 2 seconds part". how do i get the arduino to add two seconds to the current time when the LED turns off and then give my 25 millisecond reward without messing up the on/off times of the LED? Very confused.

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  • 0

    This is a classic problem when creating real-time systems (which this is, since you want things to occur at or within certain times). Writing code without an OS to provide real time capabilities is difficult. If you just try to execute things one at a time, then you get a result as shown in the first diagram below. Then when you add one more function to your program, the timing for everything is affected and your cycle execution time stretches (see the second diagram below). Then you have to try and reduce any delays in your program to compensate, and it's all an unpleasant mess.

    image

     

    You might end up with an interrupt based solution as John mentions, and that will probably meet your needs. This entails you structuring the code around the concept of timer interrupt 'ticks' and you can count them, and dispatch or execute tasks at the correct ticks (each task running to completion, so you need to make sure it finishes before the next tick). If you want to slow things down (e.g. a slow blinking LED) then you need to retain the state of the LED (on or off) and the amount of ticks that you've been in that state. And so on, for all the things you want to do in your software.

    The above is a general description, which you need to translate into software. The diagram below shows the concept. Each task must complete before the next tick.

    image

    At some point, when a program becomes more complex, you may need or want to make use of an OS, and move to a different processor probably (since OS's consume resources, probably more than the Arduino has).

  • 0 in reply to shabaz

    Hi Shabaz, What do you think of using the Arduino strictly as a time keeper and a potentiometer monitor and having it trigger astable 555 timers to complete his other subtasks? Perhaps even the use of a real time clock and interrups could eliminate the counting of clock ticks?

    John

  • 0 in reply to jw0752

    I don’t have time to document my full thoughts on this until next week but this is very doable just with the Arduino

     

     

     

    As Shabaz stated, if the requirement was more complex, then a different approach would be required but this is not a complex requirement

     

     

     

    You need the main loop to be none blocking and a set of timer variables that will be based on the output from millis(), then compared to the current Millis()

     

     

     

    A simple state machine can be setup for this with the time being reset for the delay to the next state

     

     

     

    I will try to write this up over the next few days if Im not explaining myself well enough for you to figure it out

     

     

     

     

     

    My only question is how accurate does the loop need to be to trigger the sequence

     

     

     

    You mention the LED and tone fire together for the same period, then a delay, then briefly fire the solenoid, how long before that repeats or is there some kind of manual trigger

     

     

     

    Regards

     

     

     

    Peter

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  • 0 in reply to jw0752

    I don’t have time to document my full thoughts on this until next week but this is very doable just with the Arduino

     

     

     

    As Shabaz stated, if the requirement was more complex, then a different approach would be required but this is not a complex requirement

     

     

     

    You need the main loop to be none blocking and a set of timer variables that will be based on the output from millis(), then compared to the current Millis()

     

     

     

    A simple state machine can be setup for this with the time being reset for the delay to the next state

     

     

     

    I will try to write this up over the next few days if Im not explaining myself well enough for you to figure it out

     

     

     

     

     

    My only question is how accurate does the loop need to be to trigger the sequence

     

     

     

    You mention the LED and tone fire together for the same period, then a delay, then briefly fire the solenoid, how long before that repeats or is there some kind of manual trigger

     

     

     

    Regards

     

     

     

    Peter

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