How to convert char array to int

Other Hardware Home Automation
1

i have char array "0C" i want to convert into 0x0c , i try "atoi" but its not working

2

Is the char array terminated with a zero to turn it into a C style string , which is what atoi() expects ?

Please post what you tried

3

atoi() expects base 10, not base 16 ➜ use strtol() and say you are reading something in base 16

1 Like
4

when i try "12" atoi return int 12. but when i try "0C" atoi return only 0.

5

read post #3 again...

try this

char data[] = "0C";

void setup() {
  Serial.begin(115200);
  long dataValue = strtol(data, nullptr, 16); // you coudl use an end pointer instead of nullptr to know if something went wrong
  Serial.print("I read 0x"); Serial.println(dataValue, HEX);
}

void loop() {}
6

its working .
char d3[]="00";
int reg3=(int)strtol(d3,NULL,16);
but this function also convert 0c to 12 , i want "0c" to 0c as its.

7

your variable will hold a value. This is 12 in decimal or C in hexadecimal... it's the same value, it's just a different way of printing it.

To see it in hexadecimal use
Serial.println(value, HEX);

To see it in decimal use
Serial.println(value);
or
Serial.println(value, DEC);

to see it in binary use
Serial.println(value, BIN);

if you want leading 0, you have to deal with it yourself has the print function won't add that for you.

➜

byte value = 0x0C;
if (value < 0x10) Serial.write('0');
Serial.println(value, HEX);
1 Like
8

thank , but i pass the value into array like.
outgoing.data.uint8[2] = reg3;
its oky or i want to do something to convert reg3 variable.?

9

It is okay. The 'reg3' variable contains the binary data. That is what you want, so you can use it as it is.

I made a variation. Suppose that there is a text with 8 hexadecimal numbers in it. Then I would use ssprintf() scanf() :

char text[] = "0C12D4436F000E5A";

void setup() 
{
  Serial.begin(115200);
  Serial.println( "Extract eight numbers from hexadecimal text");
  
  int x[8];
  sscanf( text, "%02X%02X%02X%02X%02X%02X%02X%02X", 
    &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7]);
  
  for( int i=0; i<8; i++)
  {
    if( x[i] < 0x10)
      Serial.print( "0");
    Serial.print( x[i], HEX);
    Serial.print( " "); 
  }
  Serial.println();
}

void loop() {}
10

Did you mean sscanf() or maybe sprintf() ?

1 Like
11

it's OK, yes. The value is the value (you have 8 bits really in memory). The way you interpret and print those 8 bits is just a user interface stuff. the bits are the same regardless of the base you want to print that out, the screen representation is different

1 Like
12

Oops, sorry, I meant sscanf(). The sketch was tested and works.

13

@J-M-L really thanks. problem solve. :slightly_smiling_face:

14

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.