Test first character in serially sent string

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

I would like to take the ASCII number and convert it to the actual character as shown in the following example program. Is there a function that will do this?

void setup(){
  Serial.begin(9600);
}

void loop()
{
  String strArray[200];
  if (Serial.available()>0)
  {
    int i = 0;
    while(Serial.available() > 0)
    {
      strArray[i] = Serial.read();
      Serial.print("Array number ");
      Serial.print(i);
      Serial.print(" is ");
      Serial.print(strArray[i]);
      Serial.print(" which is the ASCII # for the character ");
      Serial.println(strArray[i]);  // <== how can the # be converted into the character
      i++;
    }
    strArray[i] = '\0';
  }
}
#2

strArray is an array of 200 Strings... is this meant to be? Or should it be an array of 200 chars?

cast it to char? like Serial.println((char) 64);

#3

I would like to take the ASCII number and convert it to the actual character as shown in the following example program. Is there a function that will do this?

I recognize all the words in this sentence, and I even know what they all mean. Arranged in this order, though, there is little meaning.

An ASCII value is a position in a table. That position corresponds to a letter. Take the value 0x50 for instance. The character at that position in the ASCII table is 'P'. If you Serial.print(0x50), it will print the letter 'P'. If you set a char variable to 0x50, like so:

char ltr = ox50;
Serial.print(ltr);

The letter 'P' will be printed.

So, what is it you want to do?

#4

Thank you Rob and Paul. Your advice is greatly appreciated.

I was looking to test the first character in the string sent serially to the Arduino. The following code works well (thank you again). I placed a copy of the relevant section below for anyone searching for a solution to a similar issue.

void setup(){
  Serial.begin(9600);
}

void loop()
{
  char charArray[200];
  if (Serial.available()>0)
  {
    int i = 0;
    String commandString = "";
    while(Serial.available() > 0)
    {
      charArray[i] = Serial.read();
      delay(10);
      commandString = commandString + (charArray[i]);
      i++;
    }
    charArray[i] = '\0';
    if (charArray[0] == 60)  // test if the first character in string is "<" 
    {
       // if the character "<" starts the string - do some work.
    }   
}
#5 
    if (charArray[0] == 60)  // test if the first character in string is "<"

If you change the start character to something else, you need to go look up it’s ASCII value. If you do this:

    if (charArray[0] == '<')

it works the same, no comment is needed, and it’s easy to change.

#6

Once again Paul - thanks.

#7