Using a HC - SR04 Sensor to control RGB LEDS

Projects General Guidance
1

I am working on a project where I want to control RGB LEDS with a HC-SR04 sensor. Essentially what will happen is my RGB LEDS will go through a fade, but once my sensor detects an object within 31cm of it, the fade will stop and the leds will just be red.

I have a sketch that does what I mentioned above, but the sensor will not send or retrieve a signal as long as the fade is happening. So I have to wait for the fade to complete a cycle before the sensor will send out another signal. My professor told me I should look into interrupts but I'm not sure which one I should use or how they essentially work.

How would I go about using an interrupt in my project? Should I even use an interrupt? Does my code just need to be re-worked?

// ---------------------------------------------------------------------------
// Example NewPing library sketch that does a ping about 20 times per second.
// ---------------------------------------------------------------------------

#include <NewPing.h>

#define TRIGGER_PIN  12  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     11  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.
#define REDPIN 5
#define GREENPIN 6
#define BLUEPIN 3
#define FADESPEED 2

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

void setup() {
  pinMode(REDPIN, OUTPUT);
  pinMode(GREENPIN, OUTPUT);
  pinMode(BLUEPIN, OUTPUT);
  Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
  int r, g, b;
  delay(1000);                      // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
  unsigned int uS = sonar.ping(); // Send ping, get ping time in microseconds (uS).
  Serial.print("Ping: ");
  int DIS = uS / US_ROUNDTRIP_CM;
  Serial.print(DIS); // Convert ping time to distance in cm and print result (0 = outside set distance range)
  Serial.println("cm");
  
  if (31>=DIS && DIS>0) {
r = 255;
 analogWrite(REDPIN, r);
}
else
{
      for (r = 0; r < 256; r++) { 
    analogWrite(REDPIN, r);
    delay(FADESPEED);
  } 
  // fade from violet to red
  for (b = 255; b > 0; b--) { 
    analogWrite(BLUEPIN, b);
    delay(FADESPEED);
  } 
  // fade from red to yellow
  for (g = 0; g < 256; g++) { 
    analogWrite(GREENPIN, g);
    delay(FADESPEED);
  } 
  // fade from yellow to green
  for (r = 255; r > 0; r--) { 
    analogWrite(REDPIN, r);
    delay(FADESPEED);
  } 
  // fade from green to teal
  for (b = 0; b < 256; b++) { 
    analogWrite(BLUEPIN, b);
    delay(FADESPEED);
  } 
  // fade from teal to blue
  for (g = 255; g > 0; g--) { 
    analogWrite(GREENPIN, g);
    delay(FADESPEED);
  } 

}
}
2

You problem is this:

delay(FADESPEED);

Look at the blink without delay example for ideas on how to implement it better.

See here.

Or the google state machine and look at several things at once in this post.