byte b;
char temp[3];

void setup() {
  Serial.begin(115200);
}

void loop() {
  if (Serial.available() > 0) {
    String s = Serial.readStringUntil('\n');
    strncpy(temp, s.substring(0, 2).c_str(), 2);

    for (byte n=0;n<2;n++) 
      temp[n] = (temp[n]>=97 && temp[n]<=122) ? temp[n]-32 : temp[n];
    
    b =  (temp[0]<='9') ? (temp[0]-'0') : (temp[0]-'A'+10); b *= 16;
    b += (temp[1]<='9') ? (temp[1]-'0') : (temp[1]-'A'+10);
    
    Serial.print(temp); Serial.print(" "); Serial.println(b);
  }
}


/*
void str2hex( char *str, byte index ) {
  char temp[3];
  byte bytes[2] = {0x00,0x00};
  int i,
      x = 0,
      len = strlen(str); 

  //byte *base = &(mem::vfd_mem.ram[index].glyph[0]);
  for (i=0; i<len; i+=2) {
    if ((str[i] == NULL) || (str[i+1] == NULL)) break;
    strncpy(temp, &str[i], 2);
    
    for (byte n=0;n<2;n++) 
      temp[n] = (temp[n]>=97 && temp[n]<=122) ? temp[n]-32 : temp[n];

    bytes[x] =  (temp[0]<='9') ? (temp[0]-'0') : (temp[0]-'A'+10); bytes[x] *= 16;
    bytes[x] += (temp[1]<='9') ? (temp[1]-'0') : (temp[1]-'A'+10);
    x++;
  }
  for (i=0; i<5; i++) 
    mem::vfd_mem.ram[index].glyph[i] = bytes[i];
}
*/