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[on:]

Hi all,
 
I am having no end of issues with this so thought I would ask for some help guidance.

I want to convert a byte string that is send in over Serial i.e. '192' to its byte value 192. So a direct conversion as its a byte that's being sent not a string containing 192.

I have tried various methods and none seem to be working or I'm doing something wrong.

Code:

void setup () {
  Serial.begin(9600);
}

void loop(){
// Do stuff
}

void serialEvent() {
char str[3];
byte c = 0x0;
int l = 0;

while (Serial.available() > 0) {
c = Serial.read();
str[l] = c;
l++;
}

for(int i =0;i<l;i+=2) {
byte sendb = getVal(str[i]) >> 4) + getVal(str[i + 1]);
Serial.write(sendb);
}

}

byte getVal(char c)
{
   if(c >= '0' && c <= '9')
     return (byte)(c - '0');
   else if (c >= 'a' && c <= 'f')
     return (byte)(c-'a'+10)
   else
     return (byte)(c-'A'+10)
}

Above is my latest iteration which doesn't work at all tbh.

Thanks for any replies.

Modified to include full code

[Reply #1 on:]

Post the whole code not just a snippit.

What do you mean "byte string".

Mark

[Reply #2 on:]

I want to send the byte 192 via Serial to the Arduino ( atmel ) , I send this as a string. i.e "192" now I want a direct conversion so String 192 = byte 192 .

[Reply #3 on:]

I believe there's a function called atoi() for that purpose. Fairly simple to use, look it up.

[Reply #4 on:]

I believe there's a function called atoi() for that purpose. Fairly simple to use, look it up.

I was under the understanding that was a string to a int.

Which I don't *think* is the same value as a byte.

[Reply #5 on:]

Although that is actually good enough as I can do a check after to make sure its within the acceptable range 0 - 255.

Thanks!

[Reply #6 on:]

You're right, an int is 2 bytes. However it probably work the same for most purposes. Now, understand that I never actually learned C (I just picked up what I needed), but I think you can do something like
byte b 〓 atoi(chars); or maybe
byte b 〓 (byte) atoi(chars); and it will be legal (or at least compile). Don't take my word for it though. I don't have a computer here to test it.

[Reply #7 on:]

I was under the understanding that was a string to a int.

Which I don't *think* is the same value as a byte.

Correct, atoi() is intended for use with a string. However the only difference between a "byte string" as you refer to it and a string is that the final character in a string is a null. So if you receive the characters '1', '9', and '2'. Then you would simply need to pass the string '1', '9', '2', and '\0' to atoi() to get an int.

[Reply #8 on:]

Code:

for(int i =0;i<l;i+=2) {

l is really a crappy global variable name. Too hard to distinguish from one. One letter global names are rarely a good idea. One letter names are usually reserved for local (loop index) variables.

[Reply #9 on:]

Maybe a stupid question here, but if the number always fits in a byte then why send it as a string.  Just send the byte value 192 or whatever as one byte.  Then neither sender nor receiver has to do any conversions.