RX_BUF_LEN
static unsigned char rx_ring[RX_BUF_LEN+16] __attribute__((aligned(4)));
ring_offs = cur_rx % RX_BUF_LEN;
if (ring_offs+4+rx_size-4 > RX_BUF_LEN) {
int semi_count = RX_BUF_LEN - ring_offs - 4;