Convert string plus hexadecimals to array of hex:

Question

I have a string which I send to the arduino using serial monitor. Something like that:

my specific string 0x0F 0x2C 0x98 0xBC

How can I parse this string in the arduino to get an array of hex values:

0x0F 0x2C 0x98 0xBD

? There are two prerequisites:

1. All hexadecimal starts with #
2. The size of hexadecimal is 2. No 0x111 or '0xbbb'

Answer 1

How can I parse this string in the arduino to get an array of hex values:

There are a few standard library (stdlib) functions that can help you with that. Below is a snippet:

char buf[] = "0x0F 0x2C 0x98 0xBD";
uint8_t val[4];

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

  char* bp = buf;
  int i = 0;
  do {
    char* ep;
    val[i] = strtol(bp, &ep, 16);
    Serial.println(val[i], HEX);
    bp = ep;
    i += 1;
  } while (*bp != 0);
}

void loop()
{
}

Cheers!

Answer 2

You can try reading each character and convert it to hexadecimal representation. I suppose you wanna 1 byte each value in hexadecimal representation, so, let's start.

For example the string "0x25", ignore the 0x and read the '2' and save it into a char variable. Same for '5';

char highBits = '2' - '0'; // convert to decimal representation
char lowBits  = '5' - '0'; 

byte = (highBits << 4 | lowBits);

Now, save it inside you array. Make sure you check if the value is one of the possible letters in hexadecimal and convert it properly (A=10 and so on). Just include an if statement if it is a letter and convert it.