bt_att: ATT Timeout

[Marshed18]

I have uploaded nordic thingy 91 with lte_ble_gateway program and modified it so that it can connect with 7 devices, however when i try to connect the 6th device I get bluetooth error, namely bt_att: ATT Timeout

can anyone tell me how to fix this problem? is this something caused by autoconf.h, where some default parameters only support 5 devices? or is caused by connection parameters as I am using very large interval ?

static const struct bt_le_conn_param cp = {
.interval_min = 2400,
.interval_max = 2400,
.latency = 4,
.timeout = 3200,
};

or is it caused by something else?

[Hung Bui]

Hi Marshed, 

Having a connection interval of 3 seconds is quite large. Could you try the test again with small interval ? say 500ms ? 
When you receive ATT timeout, does that mean that the connection was established and then you were doing some ATT request and got a timeout ? 
Could you capture a sniffer trace of the 7th connection ? 

[Marshed18]

With smaller connection interval it works, but that is beside the point. 

and yes the connection was established and then bt_gatt_dm_start command was sent and got ATT timeout. 

how do i capture a sniffer trace ?

[Hung Bui]

You would need to have a nRF52 DK either nRF52840 or nRF52832. Then you can follow the documentation in the sniffer user manual.
With the sniffer trace we can try to compare the difference between shorter interval and longer interval.