Trying to keep my main code running unless an input is LOW for a certain amount of time

Question

I have code that creates a sequential signal with 4 LEDS. It cascades to the right. This works when I hold down the input button. What I need help with is having the code run exactly the same when there is an input signal of .5s HIGH --> .5s LOW (repeat). So what I am thinking in terms of pseudo-code is a code that keeps reading a HIGH signal as long as the signal is not low for more than .5s.

//LED outputs
int LED_5 = 6;
int LED_6 = 7;
int LED_7 = 8;
int LED_8 = 9;
//right turn signal 
int RTS_IN = A0;
//state variable for switch case statements
int stateRightTurn = 0;
//time variable
unsigned long t = 0;
//interval is the time spacing between case statements
unsigned long interval = 100;
//time for shutting off the code
unsigned long off = 600;
void setup() 
{
 Serial.begin(9600);
 
 //inputs
 pinMode(RTS_IN, INPUT);
 //right turn signal output from left to right
 pinMode(LED_5, OUTPUT);
 pinMode(LED_6, OUTPUT);
 pinMode(LED_7, OUTPUT);
 pinMode(LED_8, OUTPUT);
}
void loop() 
{
 StateRight();
}
//sequential turn signals
void StateRight()
{
 switch (stateRightTurn)
 {
 
 case 0: //idle
 if (digitalRead(RTS_IN) == HIGH)
 {
 Serial.println("0000");
 t = millis();
 SwitchRightLedsOff();
 stateRightTurn = 1;
 }
 break;
 
 case 1: //One LED On
 if (digitalRead(RTS_IN) == LOW)
 {
 Serial.println("1111-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (millis() > t + interval)
 {
 Serial.println("1111-HHHHHHHH");
 t = millis();
 digitalWrite(LED_5, HIGH);
 stateRightTurn = 2;
 }
 break;
 
 case 2: // Two LEDs On
 if (digitalRead(RTS_IN) == LOW)
 {
 Serial.println("2222-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (millis() > t + interval)
 {
 Serial.println("2222-HHHHHHHH");
 t = millis();
 digitalWrite(LED_6, HIGH);
 stateRightTurn = 3;
 }
 break;
 
 case 3: //Three LEDs On
 if (digitalRead(RTS_IN) == LOW)
 {
 Serial.println("3333-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (millis() > t + interval)
 {
 Serial.println("3333-HHHHHHHH");
 t = millis();
 digitalWrite(LED_7, HIGH);
 stateRightTurn = 4;
 }
 break;
 
 case 4: //Four LEDs On
 if (digitalRead(RTS_IN) == LOW)
 {
 Serial.println("4444-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (millis() > t + interval)
 {
 Serial.println("4444-HHHHHHHH");
 t = millis();
 digitalWrite(LED_8, HIGH);
 stateRightTurn = 5;
 }
 break;
 
 case 5: //No LEDs on
 if (digitalRead(RTS_IN) == LOW)
 {
 Serial.println("5555-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (millis() > t + interval)
 {
 Serial.println("55555-HHHHHHHH");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 break;
 } 
}
//method to switch LEDs off
void SwitchRightLedsOff()
{ 
 digitalWrite(LED_5, LOW);
 digitalWrite(LED_6, LOW);
 digitalWrite(LED_7, LOW);
 digitalWrite(LED_8, LOW);
}

• chrisl: And what is your actual question? You didn't ask one. And your description doesn't seem clear to me. Please isolate a single issue with your code, describe only this issue, what happened when you tried it and what you expected to happen.
• Myles: @chrisl I have updated main description. Let me know if that makes more sense.
• VE7JRO: If you really are going to use this in an actual vehicle, please consider what should happen with your "sequential turn signals" when the vehicle's hazard lights are flashing at the same time. What should the turn signals be doing if the brake light is on at the same time?
• Myles: @VE7JRO I have all of that code working simultaneously with the code above. I deleted it all out and segmented just this code for simplicity.
• Dave X: It isn't your issue, but you should move t to the other side of the > sign in expressions like this: (millis() > t + interval) so that you are always comparing intervals rather than timestamps. // Your proposed solution is a debouncing, or lock-out of a low inputs for 0.5s after the last observed high.

Answer 1

If I understand your requirements correctly, you could use a variable to determine if your sequential lights should be flashing or not. If the input signal is LOW for more than 1/2 second, the variable should change to LOW, telling the Arduino to stop flashing your sequential lights.

Let's pretend that your input signal is at the correct voltage and is very accurate with it's time keeping. At the 501ms mark, with no HIGH input signal, your lights should stop flashing.

A simple timer and state variable may work. Here is a test sketch.

// Sketch uses 1144 bytes (3%) of program storage space.
// Global variables use 19 bytes (0%) of dynamic memory.
class MillisTimer{
 private:
 unsigned long m_timeInMilliSeconds;
 unsigned long m_previousMillis;
 byte m_timerActive;
 public:
 MillisTimer(unsigned long timeInMilliSeconds):
 m_timeInMilliSeconds(timeInMilliSeconds),
 m_timerActive(0),
 m_previousMillis(0){
 }
 bool Update(){
 if(m_timerActive && (millis() - m_previousMillis >= m_timeInMilliSeconds)){
 m_previousMillis += m_timeInMilliSeconds;
 return 1;
 }
 else{
 return 0;
 }
 }
 void Start(){
 m_timerActive = 1;
 }
 void Stop(){
 m_timerActive = 0;
 }
 void ReStart(){
 m_timerActive = 1;
 m_previousMillis = millis();
 }
 byte IsActive(){
 return m_timerActive;
 }
};
// Make a copy of the object to work with.
MillisTimer MyTimer(501);
byte inputPin = 2;
byte signalActive = 0;
void setup(){
 // NOTE: Pull-down resistor required if input floating.
 pinMode(inputPin, INPUT);
 MyTimer.Start();
 // Timer status indicator for testing purposes.
 pinMode(LED_BUILTIN, OUTPUT);
 digitalWrite(LED_BUILTIN, LOW);
}
void loop(){
 if(digitalRead(inputPin) == HIGH){
 signalActive = 1;
 MyTimer.ReStart();
 }
 if(MyTimer.Update()){
 signalActive = 0;
 }
 // Test ouput of "signalActive" variable using built in LED on an Uno.
 if(signalActive == 1){
 digitalWrite(LED_BUILTIN, HIGH);
 }
 else{
 digitalWrite(LED_BUILTIN, LOW);
 }
 
}

• Myles: I am trying to get this work. I will let you know.

Answer 2

Assuming that digitalRead(RTS_IN) is the input, I'd read it once at the top of the loop and save the timestamp if it is HIGH, and then use the condition millis() - timestamp <= 500 as a latched input variable.

I'd also do the rest of the Input (i.e.: millis()) at the top of the function, convert the time comparisons from absolutes into intervals, and consider factoring the not-enabled case out of the switch's cases.

Untested code:

//LED outputs
int LED_5 = 6;
int LED_6 = 7;
int LED_7 = 8;
int LED_8 = 9;
//right turn signal
int RTS_IN = A0;
//state variable for switch case statements
int stateRightTurn = 0;
//time variable
unsigned long t = 0;
//interval is the time spacing between case statements
unsigned long interval = 100;
//time for shutting off the code
unsigned long off = 600;
void setup()
{
 Serial.begin(9600);
 //inputs
 pinMode(RTS_IN, INPUT);
 //right turn signal output from left to right
 pinMode(LED_5, OUTPUT);
 pinMode(LED_6, OUTPUT);
 pinMode(LED_7, OUTPUT);
 pinMode(LED_8, OUTPUT);
}
void loop()
{
 StateRight();
}
//sequential turn signals
void StateRight()
{
 const int latchInterval = 500; // ms
 static unsigned long lastHigh = -latchInterval; // initialize into the rolled-over past
 unsigned long now = millis();
 int inState = digitalRead(RTS_IN);
 if (inState == HIGH) { //update timer
 lastHigh = now;
 }
 bool enabled = (now - lastHigh <= latchInterval) ; // latched on for 500 ms after off
 switch (stateRightTurn)
 {
 case 0: //idle
 if (enabled)
 {
 Serial.println("0000");
 t = now;
 SwitchRightLedsOff();
 stateRightTurn = 1;
 }
 break;
 case 1: //One LED On
 if (!enabled)
 {
 Serial.println("1111-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (now - t > interval)
 {
 Serial.println("1111-HHHHHHHH");
 t = now;
 digitalWrite(LED_5, HIGH);
 stateRightTurn = 2;
 }
 break;
 case 2: // Two LEDs On
 if (!enabled)
 {
 Serial.println("2222-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (now - t > interval)
 {
 Serial.println("2222-HHHHHHHH");
 t = now;
 digitalWrite(LED_6, HIGH);
 stateRightTurn = 3;
 }
 break;
 case 3: //Three LEDs On
 if (!enabled)
 {
 Serial.println("3333-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (now - t > interval)
 {
 Serial.println("3333-HHHHHHHH");
 t = now;
 digitalWrite(LED_7, HIGH);
 stateRightTurn = 4;
 }
 break;
 case 4: //Four LEDs On
 if (!enabled)
 {
 Serial.println("4444-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (now - t > interval)
 {
 Serial.println("4444-HHHHHHHH");
 t = now;
 digitalWrite(LED_8, HIGH);
 stateRightTurn = 5;
 }
 break;
 case 5: //No LEDs on
 if (!enabled)
 {
 Serial.println("5555-LOWLOWLOW");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 else if (now - t > interval)
 {
 Serial.println("55555-HHHHHHHH");
 SwitchRightLedsOff();
 stateRightTurn = 0;
 }
 break;
 }
}
//method to switch LEDs off
void SwitchRightLedsOff()
{
 digitalWrite(LED_5, LOW);
 digitalWrite(LED_6, LOW);
 digitalWrite(LED_7, LOW);
 digitalWrite(LED_8, LOW);
}

• Myles: This worked perfectly! I understand it as well. I was trying to do something with the same thought process
• Dave X: The trick is turning your input(s) into the helpful "an input is LOW for a certain amount of time" timer-based state variable that your code can use.