delete string variable after executed

Projects Programming
1

im trying to use serial monitor to control arduino. it only works on the first try. I noticed that the string variable in 'msg' was not deleted, i've tried to delete the string within the variable 'msg' using the function msg = ""; for it to be ready for the next command, but it doesnt seem to work.

//library(time.h & TimeAlarms.h) installed from: http://playground.arduino.cc/Code/Time

#include <Time.h>
#include <TimeAlarms.h>
#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2
int Relay1 = 3;
int Relay2 = 4;
char state = 0;
int ledpin = 5;
String msg = "";

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);

void setup()
{ pinMode(Relay1, OUTPUT); 
  pinMode(Relay2, OUTPUT);
  pinMode(ledpin, OUTPUT);
  Serial.begin(9600);
  sensors.begin(); // IC Default 9 bit. If you have troubles consider upping it 12. Ups the delay giving the IC more time to process the temperature measurement

  setTime(8,29,0,1,1,11); // set time to Saturday 8:29:00am Jan 1 2011
  // create the alarms 
  Alarm.alarmRepeat(12,00,00, AC1on); 
  Alarm.alarmRepeat(12,05,00, AC2off);  
  Alarm.alarmRepeat(00,00,00, AC2on);  
  Alarm.alarmRepeat(00,05,00, AC1off);  
}

void  loop(){  
 
if (Serial.available()>0){
    char pdata= Serial.read();
    msg += pdata;
  

 if (msg == "lights on"){
    digitalWrite(ledpin,HIGH);
  msg = "";}
    
 else if (msg == "Lights off"){
    digitalWrite(ledpin,LOW);
  msg = "";}
    
 else if (msg == "info"){
     sensors.requestTemperatures(); // Send the command to get temperatures
     Serial.print("current Temperature is: ");
     Serial.print(sensors.getTempCByIndex(0)); // Why "byIndex"? You can have more than one IC on the same bus. 0 refers to the first IC on the wire
     Serial.println();
     Serial.print("The current time is: ");
     Serial.print(hour());
     printDigits(minute());
     printDigits(second());
     Serial.println(); 
     Serial.print("Air conditioning status: ");
     delay(1000);
     msg="";
     Serial.println(msg);
   }
   
else
{msg=="";}

 Serial.println(msg);

}}

// functions to be called when an alarm triggers:
void AC1on(){ 
  Serial.println("AC1 on");    //print "AC1 on" on serial monitor
  digitalWrite(Relay1, LOW);  //trigger AC1 relay 

}

void AC2off(){  
  Serial.println("AC2 off");    //print "AC1 on" on serial monitor
  digitalWrite(Relay2, LOW);  //trigger AC1 relay 
     
}

void AC2on(){
  Serial.println("AC2 on");    //print "AC1 on" on serial monitor
  digitalWrite(Relay2, HIGH);  //trigger AC1 relay 
}


void AC1off(){
  Serial.println("AC1 off");     //print "AC2 on" on serial monitor
  digitalWrite(Relay1, HIGH);   //trigger AC2 relay on
}


void printDigits(int digits)
{
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits);
}

when i tried to run it and type "info" in the serial monitor, this is the output

i
in
inf
current Temperature is: 27.50
The current time is: 8:29:06
Air conditioning status:

which is fine but when im going to type it over, im getting this instead,

i

in

inf

info

info

2 
msg=="";

This seems to be catching out a lot of people today. == is equality, you want assignment, =.

Although even with that, not sure it'll work, you read one character at a time, and if it doesnt match, you clear it.

Also I recommend switching to strings (char arrays) as opposed to Strings (the class).

3

well that

else
{msg=="";}

shouldnt be there actually, if i correct t. ill get no command at all as it will just delete every single character.

4

No point keeping it there if its incorrect, and to correct it would break the way the program works :wink:

Any more things you left in that need taking out before I look through?

5

nevermind, i just solved it.. i added while loop in it.. thanks for responding anyway.. :wink: