Convert Characters (A,B C) to Number (1,2,3) Characters are sent from Processing

Projects Programming
1

Hi, im sending one digit and one character from processing. E.g processing sends 1A or 1B, never more, never less than one digit + one character. I need to be able to send A-N from processing.
Arduino store the digit in 'char typeID; ' and the character in 'int motorID;'
This works but i need to convert the characters (in the motorID var) to numbers where A = 1, B=2… Which would be the easiest way of doing this?

This is how I receive the vars:

 typeID = Serial.read();                 // read it and store it in typeID
    motorID = Serial.read();                // read it and store it in motorID
    }
2 
motorID  - 'A' + 1
3

@CodingBadly,
I'm trying to follow along for learning purposes so I looked up the ASCII values for 'A' and '1' and the letters are = to '[num]'+0x30.
(ie: 1=0x31, A=0x61) so couldn't you just do 'A'-0x30 to convert 'A' to '1' ?

4

To convert 'A' to '1' instead of 1 you would do this...

motorID - 'A' + '1'

5

Assuming you got 'A' from the serial port then

x = Serial.read();
x = (x - 'A') + 1;  // () not really required

will give you an ID of 1 if that's the required relationship and it seems that it is. This translates to

65 - 65 + 1

Rob

6

Ok, I see where I got confused, that's DEC and I was trying to do with HEX.

asciifull.gif
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7

The thing to note is that the upper case letters are in order as are the lower case and the numbers.

So 'A' -'A' givers zero. Even better is that '0'-0' gives zero.

Mark

8

Hmm, thanks for all replies but Im a bit confused.

I send A from processing, then I store it in typeID. When Serial.Print(motorID); it outputs '17'.

Can't find out why A translates to 17.

EDIT*

Now I managed to make it so that sending an 'A' from processing prints an 'A'.

So when i convert it ill do
motorID=motorID - 'A' + '1';

since ill be sending A-N, how can i convert it in a smart way? Sometimes 'A' will be sent 4 times, 'N' nine times, so on… And i need N to = 14.

EDIT*

Looks like motorID=motorID - 'A' + '1'; did all the tricks! Ill do some more testing now.