Central receiving more than 23 bytes as a notification

[DavidC]

Hello community,

I am working in a central device with SDK 13 v. 4, PCA10400 (NRF52832) and SD 132 and one task is to receive 30 bytes from a sensors as a notifcation, but unfortunally I dont get anything, the MTU is already set up in ble_stack_init() as the following:

 #define NRF_BLE_MAX_MTU_SIZE    34

// Configure the MTU
memset(&ble_cfg, 0, sizeof(ble_cfg));
ble_cfg.conn_cfg.conn_cfg_tag = CONN_CFG_TAG;
ble_cfg.conn_cfg.params.gatt_conn_cfg.att_mtu = NRF_BLE_MAX_MTU_SIZE;
err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATT, &ble_cfg, ram_start);

What else should the programm have in order to receive the 30 bytes from the sensor?

Regards,

David Caraveo

[endnode]

Hi David,

MTU size is agreed on every connection (BLE stacks are usually doing it automatically at the beginning) and it will settle down on value which is minimum of both max supported values on both sides. So also your peer must be able to support larger (G)ATT MTUs. Do you have a trace from BLE sniffer to see what is happening on the radio?

[DavidC]

Thanks for the file, i'm able to check what is going on using nrf Connect to activate the notifications on the peripheral is ok but it's not receiving any notifcation, on the other hand when it tries to read the characteristics, the sniffer throws the following error: Source: Destination Protocol length Info Master Slave ATT 35 Rcvd Read Blob Request, Handle 0x0032, offset:22 Slave Master ATT 35 Rcvd Error response - Attribute not long, Handle: 0x0037 But when I am using the cysmart from Cypress in order to get the notification, i got the following: Source: Destination Protocol length Info Slave Master L2CAP 27 Rcvd Malformed packet But Im still having the data on my cellphone.