rem: apdu[i] = char_string[i];
add: apdu[i] = octet_string[i];
context: int encode_octet_string(uint8_t * apdu, const uint8_t *octet_string,  unsigned len){    unsigned i;    // limit - 6 octets is the most our tag and type could be    if (len > (MAX_APDU - 6))        len = MAX_APDU - 6;    for (i = 0; i < len; i++) {        apdu[i] = char_string[i];    }    return len;}