cc2520_read_register
ret = cc2520_read_register(priv, CC2520_RSSISTAT, &status);
ret = cc2520_read_register(priv, CC2520_RSSI, &rssi);
cc2520_read_register(priv, CC2520_FRMFILT0, &frmfilt0);
cc2520_read_register(priv, CC2520_FRMFILT0, &frmfilt0);
ret = cc2520_read_register(priv, CC2520_FSMSTAT1, &state);