Enabling Data Packet length extension

[Fabrice_31]

Hello,

Here is my configuration:

NRF52840

S140

#define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 247

I would like to enable DDLE in order to get more than 27 bytes in each transfer

On both slave and master , I saw that the DLE is activated (LL_FEATURE_REQ and LL_FEATURE_RSP)

Also, in LL_LENGTH_RSP and LL_LENGTH_REQ, RX octet =251 and TX octet=251

With that configuration, i have :

The data to be sent is 112 bytes.

Could you help to understand why the data is sent in packet of 22 byrtes?

I added the wireshark log (with nordic sniffer).

3884.log.pcapng

Thanks for your help.

Fabrice

[Sigurd]

Hi,

Looks like the master requested the data in packets of 22 bytes.

What device is the master and the peripheral ? The master is a phone? and the peripheral is a nRF52840?

[Fabrice_31]

Thanks.

The peripheral is the nRF52840. The master is a raspberry pi with a script to perform several tasks.

What is the message exchanged where the master asks for 22 bytes?

[Sigurd]

Fabrice_31 said:

What is the message exchanged where the master asks for 22 bytes?

 It's start reading an attribute, first without offset, then it continues reading the same attribute with an offset at 22 bytes increment.

[Fabrice_31]

So the raspberry ask to read an attribute and the response of the nrf52840 send 22 bytes.

Then, the raspberry asks for the following data.

Thus, on the nrf52840, it seems that there is something which send only 22 bytes (packet of 27 bytes). I tried to modify NRF_SDH_BLE_GAP_DATA_LENGTH but without success.

How to change that number of bytes sent?

[Sigurd]

I think I see it now, the raspberry does not support long MTU,