BLE over IPv6 between nrf52840 Dev kit and Rapberry 3 B+ border router : connection interface is removed after ~30 sec

[AKYR]

Hello everyone,

I'm running the IoT  CoAP example on my nrf52840 Development Kit. 

The border router is Rapberry 3 B+ on Jessie with Kernel version 4.19.46. I've put BLE_6LOWPAN_LEGACY_MODE to 0.

I've successfully connected the border router to the nrf52840 and pingued. 

My problem is that every time after approximately 30 seconds the bt0 interface goes down and the connection is lost. 

I guess it is some timeout or something that forces the interface to go down (BLE connection param : connection timeout ?) but I'm not sure how to fix it. 

I want to setup a permanent connection before trying to access the CoAP Server (nrf52840) with my CoAP Client (my computer). 

Here is the Segger log : 

<info> app: Application started.
<info> app: Physical layer in connectable mode.
<info> app: Physical layer: connected.
<info> app: Got IP Application Handler Event on interface 0x0x20004F9C
<info> app: New interface added!
<info> app: Sending Router Solicitation to all routers!
<info> app: Got IP Application Handler Event on interface 0x0x20004F9C
<info> app: Interface removed!
<info> app: Physical layer: disconnected.
<info> app: Physical layer in connectable mode.

Here is my raspberry script : 

#!/bin/sh

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
sleep 1
service radvd restart
sleep 1
modprobe bluetooth_6lowpan
sleep 1
echo 1 > /sys/kernel/debug/bluetooth/6lowpan_enable
sleep 1
hciconfig hci0 reset
sleep 1
echo "connect 00:AA:BB:CC:DD:FF 1" > /sys/kernel/debug/bluetooth/6lowpan_control
sleep 1

I can ping the nrf52840 device with its global & local address and every time the same amount of pings resolve (seq = 36).

Finaly my question is : How to prevent the bt0 interface to go down ? 

Thanks in advance,

Regars,

Aloïs KYROU

[Stian Røed Hafskjold]

Hi, seems like the data length update request from the RPi is not handled in the IoT examples: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v6.1.1/group___b_l_e___g_a_p___d_a_t_a___l_e_n_g_t_h___u_p_d_a_t_e___p_r_o_c_e_d_u_r_e___m_s_c.html?cp=3_4_1_1_2_1_3_6

Have a look at the ble_app_hrs example to see how it's been handled there.

[AKYR]

Hello Stian and thanks for your answer:) 

Just to be sure, you mean that the GAP data length update procedure is not handled by the iot_ipv6_coap_server example, which causes the Bluetooth to disconnect ? 

I thought that these examples use the Internet Protocol Support Profile that bypasses GAP and GATT protocols.

This documentation as source : https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.iotsdk.v0.9.0%2Fiot_layers.html&resultof=%22rpl%22%20

Also I tought that the ble_app_hrs  doesn't uses the IoT stack and therefore can't connect the RPi through the 6lowpan_control as I do with the CoAP example ? 

Sorry if I'm mistaking I'm new to all of this, it would be great if you could enlighten me !

Thanks in advance,

Aloïs KYROU.