NRF52 and bluez (dlen set to 27 by default)

[Constantin]

Hi,

We are developing sensors with the nRF52840. We send data packets of approx. 160 bytes with 25 Hz. We interact with a PC (Ubuntu - bluez 5.48) which works with one sensor totally fine. But if we use a second one it gets always the wrong MTU size and we can find in btmon: 

But on the nrf52 we can see that the correct MTU size is negotiated:

Are we missing something. Starting with more the than one sensor always results in a reduced data length for the first sensor while the last sensor remains with the high dlen.

Any suggestion?

Best regards,

Constantin

[Constantin]

The errors prompted by btmon are:

unexpected start frame followed by unexpected continuation

[bjorn-spockeli]

HI Constantin, 

are you able to capture a trace of the on air data packets using the nRF Sniffer v2? By looking at the on air date we should be able to see if the correct dlen is communicated to bluez or not. 

Best regards

Bjørn

[Constantin]

Okay found the issue. It was the GAP_LENGTH in combination with BT4.0 dongle. It seems that there are only few dongles and laptops supporting BLE4.2 available.