Stop Program looping

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hi

This is my first time at trying to program anything.

I have the Arduino Duemilanove Board.

I am trying to get the board to switch on or off 8 relays.

I have modified some code I have found on the internet and I am able to switch the 8 relays on and off ok. But the problem I am having is the command is being repeated so the relay is constantly switching on and off.

What I want is for a pulse to switch the relay on for 1 second then switch the relay off and wait for the next command.

here is the code I am using.

char val;         // variable to receive data from the serial port 
int ledpin = 2;  // LED connected to pin 2 to 9 (on-board LED) 

void setup() 
{ 
  pinMode(ledpin = 2, OUTPUT);  // pin 2 (on-board LED) as OUTPUT 
  pinMode(ledpin = 3, OUTPUT);  // pin 3 (on-board LED) as OUTPUT 
  pinMode(ledpin = 4, OUTPUT);  // pin 4 (on-board LED) as OUTPUT 
  pinMode(ledpin = 5, OUTPUT);  // pin 5 (on-board LED) as OUTPUT 
  pinMode(ledpin = 6, OUTPUT);  // pin 6 (on-board LED) as OUTPUT 
  pinMode(ledpin = 7, OUTPUT);  // pin 7 (on-board LED) as OUTPUT 
  pinMode(ledpin = 8, OUTPUT);  // pin 8 (on-board LED) as OUTPUT 
  pinMode(ledpin = 9, OUTPUT);  // pin 9 (on-board LED) as OUTPUT 
  Serial.begin(9600);       // start serial communication at 9600bps 
  Serial.println("Press 1 - 9 to toggle relay on/off");
} 
 
void loop() { 
  if( Serial.available() )       // if data is available to read 
  { 
    val = Serial.read();         // read it and store it in 'val' 
  } 
  if( val == '2' )               // if '2' was received 
  { 
    digitalWrite(ledpin = 2, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 2 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
    
  }
if( val == '3' )               // if '3' was received
 { 
    digitalWrite(ledpin = 3, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 3 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  } 
  if( val == '4' )               // if '4' was received
  { 
    digitalWrite(ledpin = 4, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 4 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
  if( val == '5' )               // if '5' was received
  { 
    digitalWrite(ledpin = 5, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 5 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
  if( val == '6' )               // if '6' was received
  { 
    digitalWrite(ledpin = 6, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 6 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
  if( val == '7' )               // if '7' was received
 { 
    digitalWrite(ledpin = 7, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 7 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
  if( val == '8' )               // if '8' was received
  { 
    digitalWrite(ledpin = 8, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 8 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
  if( val == '9' )               // if '9' was received
  { 
    digitalWrite(ledpin = 9, HIGH);  // turn ON the LED 
    delay(1000);                  // waits for a second
    Serial.println("Relay 9 on");
    digitalWrite(ledpin, LOW);    // sets the LED off
  }
}

Please can someone tell me where I'm going wrong.

Simon

2

Once you've processed a valid "command" using val, then you can set the val to a "do nothing" value until there's more input available.

Or you can move the "}" that you put right after the Serial.read() call. Move it to the end of the if statements. This will then only check the val immediately after a read, not on every loop.

3

Remember loop() loops constantly, forever. What is happening is tat every time loop() executes when there is no data, you still execute your if block and switch a relay. They way your program is structured it happens to be the last one you switched.

One way to stop that would be to wait until there is a character available before continuing the loop. This would cause loop() to block (stop execution) until it got a character to read.

Instead of the code

  if( Serial.available() )       // if data is available to read
  {
    val = Serial.read();         // read it and store it in 'val'
  }

try this

  while (Serial.available() <1 )  // wait until there is data to read
  {;}
  val = Serial.read();         // read it and store it in 'val'

-j

4

Hi

Thanks for the quick response.

It's working perfectly now.

Thanks

Simon