If statement does not work?

Projects Programming
1

Hello people,

I have the followong code:

#include <AltSoftSerial.h>
#include <FileIO.h>
#include <Process.h>

AltSoftSerial altSerial;

// Incoming data
char     sReceived[19];     // The valid string can contain 18 bytes and a terminating null

void setup() {
  Bridge.begin();	// Initialize the Bridge
  Serial.begin(9600);	// Initialize the Serial
  FileSystem.begin();
  // Wait until a Serial Monitor is connected.
  while(!Serial);

  altSerial.begin(4800);
}

void loop(){
  char   cByte     = -1;
  char   cStatus   = -1;
  String sHexChar  = "";
  
  if (altSerial.available()) {
    // Create a string array with the complete data
    cByte = altSerial.read(); 
    AddToReceived(cByte);
    
    // See if the string matches a valid string (yet)
    if ( MatchPattern() ) {
      cStatus = getStatus();
      
      sHexChar = CharToHex(cStatus);
      Serial.println("Status Hex = " + sHexChar );
      Serial.println("Status Chr = " + CharToHex(cStatus) );
      
// Do something with status 00	  
//      if (cStatus = '\0' )
//      if (CharToHex(cStatus) = "00" ){
      if (sHexChar = "00" ){
        Serial.println("-----> Status is '00'");
        StatusMessage(cStatus);
      }
      
// Do something with status 21	  
//      if (cStatus = '\21') 
//      if (CharToHex(cStatus) = "21"){ 
      if (sHexChar = "21"){ 
        Serial.println("-----> Status is '21'");
        StatusMessage(cStatus); 
      }
    }  
  }
}


//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
void StatusMessage(char cChar){
	Serial.println("Status is: '" + (String)cChar +  "'"); // For now, just print it
}

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
char getStatus(){
  return sReceived[12];
}

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
void AddToReceived(char cByte)
{ // sReceived is a global variable
  // We add information ad the end, discarding each first character when we reached a full buffer
  //                       0   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18 
  // Example sReceived = [  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][01][02][03]
  // becomes sReceived = [  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][  ][01][02][03][04]
  // and
  // Example sReceived = [01][02][03][04][05][06][07][08][09][0a][0b][0c][0d][0e][0f][10][11][12][13]
  // becomes sReceived = [02][03][04][05][06][07][08][09][0a][0b][0c][0d][0e][0f][10][11][12][13][14]

  // Shift all characters one position to the left and add the new character to the new position
  for (int i=0; i <= 17; i++){
    sReceived[i] = sReceived[i+1];
  }
  sReceived[18] = cByte;  
}

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
String CharToHex (char cByte)
{ String sHex = "";
  // Get the character received and return the same information converted to it's hexadecimal form.
  sHex  = "0" +String(cByte,HEX);            // Put a zero in front of each value, making '0' into '00' and '11' into '011' and 'ffa3' into '0ffa3'
  sHex  = sHex.substring(sHex.length()-2);   // Get the last two characters, leaving '00' at '00' and turning '011' to '11' and even '0ffa3' into 'a3'
  return sHex;  
}

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
boolean MatchPattern()
{
  if (sReceived[17] == '\3')              // STX byte (Start of transmission) 
    if (sReceived[ 1] == '\2')            // ETX byte (End   of transmission)
      return true;                        // Yup.... This is the one!

  // No match.... So return false.
  return false;
}

The part that is giving me headaches is this:

// Do something with status 00	  
//      if (cStatus = '\0' )
//      if (CharToHex(cStatus) = "00" ){
      if (sHexChar = "00" ){
        Serial.println("-----> Status is '00'");
        StatusMessage(cStatus);
      }
      
// Do something with status 21	  
//      if (cStatus = '\21') 
//      if (CharToHex(cStatus) = "21"){ 
      if (sHexChar = "21"){ 
        Serial.println("-----> Status is '21'");
        StatusMessage(cStatus); 
      }

Why?
Well.... see my output in the Serial Monitor:

Status Hex = 00
Status Chr = 00
-----> Status is '00'
[StatusMessage] Status is: ' '
-----> Status is '21'
[StatusMessage] Status is: ' '

I have tries every form of comparing I can imagine.
(Some of them are still in the comments)
Both if-statements will produce results and I don't get it.
How come?
Do I test the wrong variables?
Do I need an other way of comparing?

I just don't see the problem, and being more and more creative did not help me.
Please tell me what is wrong with my ways of comparing

2 
      if (sHexChar = "00" ){

This is an assignment statement, not an equality test.

= != ==

3

if (cStatus = '\21') --- this statement sets the value of cStatus to '\21' and then checks to see of cStatus is non-zero which it now is.

What you want is

if (cStatus == '\21')

Bites us all one time or another.

4 
 if (sHexChar == "21")

won't work either, you compare strings with strcmp, not ==

5 
you compare strings with strcmp, not ==

But, sHexChar isn't a string. It's a String, with a piss poor name.

6

MarkT:

 if (sHexChar == "21")

won't work either, you compare strings with strcmp, not ==

PaulS:
But, sHexChar isn't a string. It's a String, with a piss poor name.

sHexChar ........
My vision in naming the variable was: It's a String, hence 's'.
It's a HEX notation of the char variable, hence HexChar.
So..... that's how I came to sHexChar. But I'm allways open to suggestion to better myself. :slight_smile:

The if statement.....It's a newbie error, I acknowledge that. :slight_smile:
And if (sHexChar == "21") works.
(BTW: I did try the '==' before I posted and got an error that I was mixing C and C++ commands........)
Thanks for the assistance. The correct message it send at the correct time now.. :slight_smile:

However..... I get the feeling from you comments, there is a better way to work with stings.
Can you direct met to some reading material, or just explain me what to do better?

7

Don't get too concerned about other people's opinions. If the variable means something to you, it's good.

8

If the variable means something to you, it's good.

Unless is only means something today.

I've seen crap like this:
int myFloat;
float myInt;
int someFloats[] = {5, 6, 7};

While the names might have meant something when the code was created, a week later, they wont.

To me, char in a name implies ONE character. chars implies more than one. sHexChars is would have cringed, but passed on. sHexValue I would have accepted. sHexString is a better description of what the variable contains, and would have been acceptable to me Except for using the useless String class in the first place.

9

I see. Maybe sCharInHex wouldv'e been more descriptive, if not a bit long. Keep in mind though, it is one char, just in hex notation, which takes two digits to represent one byte (char).