BLE params on nRF53

RE: BLE params on nRF53

dejans — Thu, 20 Jan 2022 16:33:55 GMT

Hi Mehdi,

1. A standard data length of radio packets in Bluetooth Low Energy is 27 bytes. It means that CONFIG_BT_CTLR_DATA_LENGTH_MAX is set to 27 bytes. You need to have a proper configuration in the child_image folder which would replace default one. You could try using the following options:
CONFIG_BT_BUF_ACL_TX_SIZE=251 //Maximum supported ACL size for outgoing data
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 //Maximum data length supported
CONFIG_BT_BUF_ACL_RX_SIZE=251 //Maximum supported ACL size for incoming data
CONFIG_BT_MAX_CONN=2 //Maximum number of simultaneous connections

There are two ways to handle setting of both parameters. One is to disable bt_conn_le_data_len_update function. In this case, Bluetooth stack would handle that on your behalf. The second way is to repeat procedure of requesting the length.

2. nrf\samples\bluetooth\throughput\prj.conf defines needed options for the throughput example. hci_rpmsg.conf defined in child_image folder contains additional configuration options.

3. Devices agree on MTU value through the negotiation. process.

4. Similar to gat event length, you should consider using CONFIG_SDC_MAX_CONN_EVENT_LEN_DEFAULT (default max connection event length)

Best regards,
Dejan

RE: BLE params on nRF53

Mehdi — Wed, 19 Jan 2022 14:57:01 GMT

Hi Dejans,

I want first to thank you for your reply.

Thank you, I'm running the throughput test as a peripheral, and once connected to the mobile I used

bt_conn_le_data_len_update to update data length, It works with the TX params but the RX data length is maintained to 27 bytes. Knowing that through bt_conn_le_data_len_update it's possible to set only the TX params(max length and timeout), is there any way to set both RX and TX params?
Based on the throughput example, CONFIG_BT_L2CAP_TX_MTU symbol which I think is related to the BLE MTU is set under the configuration file of the application core, is there any other symbol related to the MTU that should be set to the network configuration file ?
Following the link, the bt_gatt_exchange_mtu function could only trigger a request to exchange MTU, but I don't see how can I set my preferred MTU.
Is there any way to exchange GAP event length like nRF52 using the softdevice S132?

Best Regards,

Mehdi.

RE: BLE params on nRF53

dejans — Tue, 18 Jan 2022 14:35:55 GMT

Hi Mehdi,

1. For nRF5340-DK, the additional configuration options for the network core such as CONFIG_BT_CTLR_DATA_LENGTH_MAX are taken from the "child_image" directory.
Please have a look at multi-image-builds and configuration of the child image.
There is an example of the configuration file inside change_image folder in nrf\samples\bluetooth\throughput\child_image\hci_rpmsg.conf.
2. Yes, these parameters are related to the bluetooth controller and they should be associated with the network core
3. Menuconfig is the place where you set your MTU value. However, you can change this on runtime by using bt_gatt_exchange_mtu function. You can read more on the developer page exchange MTU.

Best regards,
Dejan