IOS:Convert string to hexadecimal array

Question

i have string representing data .i need to convert those data to the hex array .By using the hex array data i can pass it to the CRC for writing to the peripheral

M

Answer 1

A. The hexadecimal format is simply another representation of the same data.

B. You do not convert them into hex array. Every character has a number. For example in ASCII and UTF-8 the A has the number 65 (decimal representation). This is 0x41 in hex representation.

'A' (ASCII) == 65 == 0x41.

A hex number has the the digits 0-9, a-f, wherein a has the value of 10, b the value of 11 … It is converter into decimal representation by multiplying the upper digit by 16 and adding the lower digit. (0x41: 4 x 16 + 1 = 65.)

Please read and understand this: http://en.wikipedia.org/wiki/Hexadecimal

C. To convert a string into its number, you have to know, which code you want to apply. Probably you want to use UTF-8.

NSString *text = @"helloworld123123989128739";
NSUInteger length = [text lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
char data[length];
[text getCString:data maxLength:length usingEncoding:NSUTF8StringEncoding];
// Here we go