Hello all, I have found closed topics here with similar names (devzone.nordicsemi.com/.../ etc.) but my question is about adding the characteristic with encryption. My device is nrf51822 s130. I want to create encrypted link with the central by NUS (Nordic Uart Service).
I added service and want to add TX characteristic with:
char_md.char_props.write = 1;
char_md.char_props.write_wo_resp = 1;
...
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&attr_md.read_perm);
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&attr_md.write_perm);
and call sd_ble_gatts_characteristic_add that successfully finished. I've tested encryption by sending packets from central with and without bonding, without being bonded my device didn't receive the packets. So I think encryption works on this direction.
The different situation is with RX characteristic (full code). I want to notify to peer central.
memset(&cccd_md, 0, sizeof(cccd_md));
/*BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM*/
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm); //**But why???**
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&cccd_md.write_perm);
cccd_md.vloc = BLE_GATTS_VLOC_STACK;
memset(&char_md, 0, sizeof(char_md));
char_md.char_props.notify = 1;
char_md.p_char_user_desc = NULL;
char_md.p_char_pf = NULL;
char_md.p_user_desc_md = NULL;
char_md.p_cccd_md = &cccd_md;
char_md.p_sccd_md = NULL;
ble_uuid.type = gs_central.uuid_type;
ble_uuid.uuid = BLE_UUID_NUS_RX_CHARACTERISTIC;
memset(&attr_md, 0, sizeof(attr_md));
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&attr_md.read_perm);
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&attr_md.write_perm);
attr_md.vloc = BLE_GATTS_VLOC_STACK;
attr_md.rd_auth = 0;
attr_md.wr_auth = 0;
attr_md.vlen = 1;
memset(&attr_char_value, 0, sizeof(attr_char_value));
attr_char_value.p_uuid = &ble_uuid;
attr_char_value.p_attr_md = &attr_md;
attr_char_value.init_len = sizeof(uint8_t);
attr_char_value.init_offs = 0;
attr_char_value.max_len = BLE_MAX_DATA_LEN;
if ((err_code=sd_ble_gatts_characteristic_add(gs_central.service_handle, &char_md, &attr_char_value, &gs_central.rx_handles)) != NRF_SUCCESS){
DBG("sd_ble_gatts_characteristic_add RX: %d\n",err_code);
return;
}
The error NRF_ERROR_INVALID_PARAM occured during sd_ble_gatts_characteristic_add wthen cccd_md.read_perm set to be encrypted.
BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(&cccd_md.read_perm);
when no encryption chosen ( BLE_GAP_CONN_SEC_MODE_SET_OPEN ) there are no error.
The question #1 is why the error occured?
The question #2 : Could RX direction of link be considered encrypted with BLE_GAP_CONN_SEC_MODE_SET_OPEN on cccd_md.read_perm?
Best regards,
