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reading from an array

Former Member

hey guys whats up, so i am parsing an sms message into an array, i am able to get the sms message, but i am having trouble comparing the sms to values, for eg,the sms is 9, i am getting problems comparing the value.

Below is my code

 

char character = 0;
char data[255];
int x=0;
int openingroof =53;
int closingroof =51;
int turningbeans = 52;
int buzzer = 49;
int manual_drawopenled =50;
int manual_drawcloseled = 48;
int smsled = 47;
void setup()
{
  Serial.begin(9600);
  Serial1.begin(9600);
  delay(60000);


pinMode(openingroof,OUTPUT);
pinMode(closingroof,OUTPUT);
pinMode(turningbeans,OUTPUT);
pinMode(buzzer,OUTPUT);
pinMode(manual_drawopenled,OUTPUT);
pinMode(manual_drawcloseled,OUTPUT);
pinMode(smsled,OUTPUT);


Serial1.println("AT+CMGF=1");
}


void smsrecieve()
{
  
  Serial1.println("AT+CMGR=1"); //Reads the first SMS
Serial1.flush();
for (x=0;x < 255;x++){ 
data[x]='\0'; 
} 
x=0;
do{
while(Serial1.available()==0);
data[x]=Serial1.read(); 
x++; 
if(data[x-1]==0x0D&&data[x-2]=='"'){
x=0;
}
}
while(!(data[x-1]=='K'&&data[x-2]=='O'));


data[x-3]='\0'; //finish the string before the OK


}


void loop()
{


smsrecieve();


if (data=="9")
{
  digitalWrite(smsled,HIGH);
  
}


}

 

What happens is data is the array and the sms message is "9". Serial printin data will also show 9. Any ideas?

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  • 0

    Hi,

     

    (Assuming Arduino-language is the same as C), it looks like the immediate problem is that the you're trying to compare a string:

    if (data=="9")
    {
      digitalWrite(smsled,HIGH);
     
    }

    This won't give you what you're looking for. You need to do something like

    if (data[0]=='9')

    which will check the first byte. Alternatively, you can look for a string compare function.

     

    Also, the smsreceive() function looks very irregular, because you're checking things like data[x-2] when you know that x may be under-range for the array. I can see you've tried to compensate for that by defining a dummy character before you define the array.

     

    A better way to implement this sort of stuff is to create a state machine. In C one simple way consists of switch..case statements. There are some more advanced methods, but the switch..case method is fine for simple scenarios and is easy to understand. Here is how it works:

    Your states would be enumerated somewhere, and then you'd use a single byte to store your state.

    So, (for example) if you were expecting (say) the characters ", 9, ", <carriage return> (I don't know if that's what you were expecting, but

    let's use this as an example), then your possible states may be called START, INSTRING, DONESTRING, FINISHED.

    You'd use a switch(statevar) command, and have the case: statements checking for the different state values.

    You'd move to state INSTRING as soon as you see a quote arrive, but only if you were in state START initially.

    You'd move to state DONESTRING as soon as you see a quote arrive, but only if you were in state INSTRING.

    You'd move to state FINISHED whenever you saw a carriage return, regardless of state

    You'd quit the smsreceive() function whenever you reached FINISHED state.

    You get the idea..

     

    Something like:

     

    mystate=START;

    do

    {

      inchar=readchar();

      switch(mystate)

      {

        case START:

          if (inchar=='"')

            mystate=INSTRING;

          break;

        ... etc

      }

    }while(mystate!=FINISHED);

     

     

    State machines solve these types of programming problems quite well.

Reply
  • 0

    Hi,

     

    (Assuming Arduino-language is the same as C), it looks like the immediate problem is that the you're trying to compare a string:

    if (data=="9")
    {
      digitalWrite(smsled,HIGH);
     
    }

    This won't give you what you're looking for. You need to do something like

    if (data[0]=='9')

    which will check the first byte. Alternatively, you can look for a string compare function.

     

    Also, the smsreceive() function looks very irregular, because you're checking things like data[x-2] when you know that x may be under-range for the array. I can see you've tried to compensate for that by defining a dummy character before you define the array.

     

    A better way to implement this sort of stuff is to create a state machine. In C one simple way consists of switch..case statements. There are some more advanced methods, but the switch..case method is fine for simple scenarios and is easy to understand. Here is how it works:

    Your states would be enumerated somewhere, and then you'd use a single byte to store your state.

    So, (for example) if you were expecting (say) the characters ", 9, ", <carriage return> (I don't know if that's what you were expecting, but

    let's use this as an example), then your possible states may be called START, INSTRING, DONESTRING, FINISHED.

    You'd use a switch(statevar) command, and have the case: statements checking for the different state values.

    You'd move to state INSTRING as soon as you see a quote arrive, but only if you were in state START initially.

    You'd move to state DONESTRING as soon as you see a quote arrive, but only if you were in state INSTRING.

    You'd move to state FINISHED whenever you saw a carriage return, regardless of state

    You'd quit the smsreceive() function whenever you reached FINISHED state.

    You get the idea..

     

    Something like:

     

    mystate=START;

    do

    {

      inchar=readchar();

      switch(mystate)

      {

        case START:

          if (inchar=='"')

            mystate=INSTRING;

          break;

        ... etc

      }

    }while(mystate!=FINISHED);

     

     

    State machines solve these types of programming problems quite well.

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