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]

I dont have any sniifer, I am using pca10040 and the sniffer program does not support it. I've a doongle of Cypress company and it receives the 30 bytes via notication but when I use nRF connect with my pca10040 I can not receive any notification and if i read them it returns an error:

Read operation failed: BLE_GATT_STATUS_ATTERR_ATTRIBUTE_NOT_LONG (0x010B)

why do you know i cannot get this 30 bytes?