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?

[Bjørn Kvaale]

Hi DavidC. As Endnode mentioned, there is an unofficial sniffer app for the nrf52. You can find it here. Could also be useful to look at the nrf sniffer user guide here.