Running loop for a specific time period

Question

I currently have a loop that runs without a time condition:

unsigned long previousMillis = 0;        // will store last time LED was updated

int WET=4;//wet line
int DRY=5;//dry line
int Inhale=1000;//msec
int Exhale=1000;//msec
//int Noflow=3000;//msec

void setup() {
  // put your setup code here, to run once:
  pinMode (WET, OUTPUT);
  pinMode (DRY, OUTPUT);
}

void loop() {
  //inhale
  digitalWrite(WET,LOW);
  digitalWrite(DRY,HIGH);
  delay (Inhale);
  //exhale
  digitalWrite(WET,HIGH);
  digitalWrite(DRY,LOW); 
  delay (Exhale);
  //No flow
  //digitalWrite(WET,HIGH);
  //digitalWrite(DRY,HIGH);
  //delay (Noflow);
}

Then i have tried to code a "timer" for each cycle,but i got error:" exit status 1 Error compiling for board Arduino/Genuino Uno."

Code with timer:

unsigned long previousMillis = 0;        // will store last time LED was updated

int WET = 4; //wet line
int DRY = 5; //dry line
//int Inhale=1000;//msec
//int Exhale=1000;//msec
//int Noflow=1000;//msec
int BPM = 60;
int IE = (((60 * 1000) / BPM) / 2);

void setup() {
  // put your setup code here, to run once:
  pinMode (WET, OUTPUT);
  pinMode (DRY, OUTPUT);
}

void loop() {
  for (int i = 0; i = 20;)
    int BPM = BPM + 10;
#include <elapsedMillis.h>

  elapsedMillis timeElapsed;
  unsigned int interval = 60000; //one minute in ms

  while (timeElapsed < interval) {

    //inhale
    digitalWrite(WET, LOW);
    digitalWrite(DRY, HIGH);
    delay (IE);
    //exhale
    digitalWrite(WET, HIGH);
    digitalWrite(DRY, LOW);
    delay (IE);
    //No flow
    //digitalWrite(WET,HIGH);
    //digitalWrite(DRY,HIGH);
    //delay (2000);
  }
}

Target ouput: to run every cycle of the loop for 1 min.

Any one familiar with this error? Many thanks for your help

Answer 1

Your code has a number of problems:

Don't put #include statements for header files in the middle of your code. They belong at the top, before any other code. (What is the header file elapsedMillis.h?)

Another thing: Your for loop is a mess. It should read something like: for (int i = 0; i < 20; i++) (That would cause the for loop to run 20 times, with the value of i ranging from 0 to 19.) However, what do you want to happen in your for loop? Without braces after that code, the ONLY line that will execute 20 times is the int BPM = BPM + 10; line (which doesn't make any sense.)

You really shouldn't use time-based while loops inside your main loop function. That defeats the purpose of using timers instead of delay statements. And you should get rid of your calls to delay() and use millis() to manage all your timing. Do a search on "Arduino blink no delay" and study the examples for information on how to restructure your code.