gistfile1.txt

setInterval(() => {
  new Promise((resolve, reject) => {
    ...
    resolve(value);
    ...
  }).then((value) => { ... }); 
}, 100);

gistfile2.txt

let digitalReadPromise = (pin) => {
  let thePin = pin;
  return new Promise( (resolve, reject) => {
    setTimeout(() => { resolve(); }, 10); // wait 10 milliseconds
  }).then(() => {
    return new Promise((resolve, reject) => {
      gBoard.digitalRead(thePin, function(value){
        resolve(value);
      });
    });
  });
};

setInterval(() => {
      if(statusObj['status'] == "ready") {
        // check for the start button being pressed
        digitalReadPromise(START_BUTTON_PIN).then((value) => {
          if (value == 0) {
            return digitalReadPromise(CALIBRATE_FANS_BUTTON_PIN);
          }
          else {
            return -1;
          }
        }).then((value) => {
          if(value != -1) {
            if (value == 0) {
              // execute code for case 1
            }
            else if(do_fan_calibration == 1){ // fan calibration button is NOT pressed
              // execute code for case 2
            }
          }
        });
      }
    }, 100); // check every 100 milliseconds