char *byte2hex(char *s, uint8_t b) {
    static char hex[] = {
        '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
    };

    *s++ = hex[ (b >> 4) & 0x0F ];
    *s++ = hex[ b & 0x0F ];
    return s;
}


char buffer[12345314123565123567865];
uint16_t id[...];
char *p = buffer;

for (size_t i = 0; i < ...; i++) {
    p = byte2hex(p, id[i] >> 8);
    p = byte2hex(p, id[i]);
}