Arduino char数组为整数值

Question

Stupid question here:

I'm trying to convert a char array to a integer number. This is my case (extracted from main code, I've simplyfied it..):

int val;
char *buff;
uint8_t v1 = 2;
uint8_t v2 = 25;

buff[0] = v1;
buff[1] = v2;
val = strtol(buff, NULL, 16);

In that situation the val returns always '0' but, if I replace 'buff' with "0x225", it returns the expected value of 549.

What I'm doing wrong? Thanx in advance..

Answer 1

you need to learn C (C++ actually as arduino is programmed in C++).

strtol converts strings to numbers.

string in C is a array of char elements ending with zero (not '0' but 0 ). So "0x225" is the array of {'0', 'x', '2', '2', '5', 0}

'2' is not the number 2 . It is ASCII representation of char '2' which is 50 in decimal.

buff[0] = '0';
buff[1] = 'x';
buff[2] = '2';
buff[3] = '2';
buff[4] = '5';
buff[5] = 0;

val = strtol(buff, NULL, 16);


buff[0] = 48;
buff[1] = 120;
buff[2] = 50;
buff[3] = 50;
buff[4] = 53;
buff[5] = 0;

val = strtol(buff, NULL, 16);

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your code has many other issues. You need to understand what 25 and what 0x25 is (they are not equal). You should start from the book and PC compiler and learn language from the very basic stuff.