Hello friends,
I am working on STM32WB on-chip Bluetooth low energy system to transmit data from server to client using notification property.
I want to transmit 46 bytes at the rate of 500Hz without any packet loss, to achieve this I have updated the following BLE connection parameters-
- MTU Size: 512 Bytes
- hci_le_set_data_length: 251 Bytes with Tx time: 2120 ms
- Connection Interval: 11.25ms
- TX_PHY & RX_PHY: 2M
- Tx Power: 4dBm
but I face data loss at the receiver end.
To transmit 46 bytes of data using notify, I update the p2p service and Characteristic as-
/**
* Peer To Peer Service
*
* Max_Attribute_Records = 2*no_of_char + 1
* service_max_attribute_record = 1 for Peer To Peer service +
* 2 for P2P Write characteristic +
* 2 for P2P Notify characteristic +
* 1 for client char configuration descriptor +
*
*/
COPY_P2P_SERVICE_UUID(uuid16.Char_UUID_128);
aci_gatt_add_service(UUID_TYPE_128,
(Service_UUID_t *) &uuid16,
PRIMARY_SERVICE,
8,
&(aPeerToPeerContext.PeerToPeerSvcHdle));
/**
* Add LED Characteristic
*/
COPY_P2P_WRITE_CHAR_UUID(uuid16.Char_UUID_128);
aci_gatt_add_char(aPeerToPeerContext.PeerToPeerSvcHdle,
UUID_TYPE_128, &uuid16,
BA_RX_DATA_PACKET_SIZE,
CHAR_PROP_WRITE_WITHOUT_RESP|CHAR_PROP_READ,
ATTR_PERMISSION_NONE,
GATT_NOTIFY_ATTRIBUTE_WRITE, /* gattEvtMask */
10, /* encryKeySize */
1, /* isVariable */
&(aPeerToPeerContext.P2PWriteClientToServerCharHdle));
/**
* Add Button Characteristic
*/
COPY_P2P_NOTIFY_UUID(uuid16.Char_UUID_128);
aci_gatt_add_char(aPeerToPeerContext.PeerToPeerSvcHdle,
UUID_TYPE_128, &uuid16,
249,
CHAR_PROP_NOTIFY,
ATTR_PERMISSION_NONE,
GATT_NOTIFY_ATTRIBUTE_WRITE, /* gattEvtMask */
10, /* encryKeySize */
1, /* isVariable: 1 */
&(aPeerToPeerContext.P2PNotifyServerToClientCharHdle));
And send data from server to client using function -
tBleStatus P2PS_STM_App_Update_Char(uint16_t UUID, uint8_t *pPayload, uint8_t length)
{
tBleStatus result = BLE_STATUS_INVALID_PARAMS;
switch(UUID)
{
case P2P_NOTIFY_CHAR_UUID:
result = aci_gatt_update_char_value(aPeerToPeerContext.PeerToPeerSvcHdle,
aPeerToPeerContext.P2PNotifyServerToClientCharHdle,
0, /* charValOffset */
length, /* charValueLen */
(uint8_t *) pPayload);
break;
default:
break;
}
return result;
}
I need your tips and guidance to get lossless transmission using BLE.
