连接稳定性问题

Hi Dialog,

I am developing a pair of BLE device, both server and slave, base on DA14580. After connected to each other, even I leave these processor to be idle(no BLE read/write/notify, no i2c, gpio... active ) but they still disconnect randomly. It looks like one of them corrupts in link layer, because after disconnect they could not reconnect again. Below are the parameters I set for this connection and some wireshark captures.

msg-> nb_peers = 1;
memcpy((void *) &msg->peers[0].addr, (void *)peer_addr, BD_ADDR_LEN);
msg->peers[0].addr_type = peer_addr_type;
msg-> con_intv_max = 10;
msg-> con_intv_min = 10;
msg-> ce_len_max = 0x20;
msg-> ce_len_min = 0x20;
msg-> con_latency = 0;
msg-> superv_to = 100;
msg-> scan_interval = 0x180;
msg-> scan_window = 0x160;
msg-> op.code = gapm_connection_direct;

wireshark capture:

9796 61.273854000主从机BLE数据26空数据PDU
9797 61.275295000 Slave Master BLE Data 26 Empty Data PDU
9798 61.286603000 Master Slave BLE Data 26 Empty Data PDU
9799 61.287569000从站主机BLE数据26空数据PDU
9800 61.298855000主从电池数据26空数据PDU
9801 61.299789000 Slave Master BLE Data 26 Empty Data PDU
9802 62.320227000 AB_MAT5 BLE ADV 48 ADV_IND
9803 62.321788000 ab_mat5 BLE ADV 48 ADV_IND

服务器和客户端保持60s的连接，无法相互连接。

I could still see slave side advertising, but even use an Iphone with LightBlue application, I could not connect to the slave anymore.
Wireshark capture:
25 6.273182000 ab_mat4 BLE ADV 48 ADV_IND
26 6.274736000 50：0B：F8：18：AC：29 80：EA：CA：00：00：41 BLE ADV 60 Connect_Req
27 6.276461000主从机BLE数据26空数据PDU
28 6.303327000主从机BLE数据26空数据PDU
29 6.333342000主从机BLE数据26空数据PDU
30 6.363329000主从机BLE数据26空数据PDU
31 6.393384000主从机BLE数据26空数据PDU
32 6.423327000主从机BLE数据26空数据PDU
33 6.453367000主从机BLE数据26空数据PDU
34 6.483385000主从机BLE数据26空数据PDU
35 6.513421000主从机BLE数据26空数据PDU
36 6.543378000主从机BLE数据26空数据PDU
37 6.573448000主从机BLE数据26空数据PDU
38 6.603361000 Master Slave BLE Data 26 Empty Data PDU
39 6.633361000 Master Slave BLE Data 26 Empty Data PDU
40 7.640482000 AB_MAT4 BLE ADV 48 ADV_IND
41 7.642505000 AB_MAT4 BLE ADV 48 ADV_IND

In this test, I set the connection interval to be 12.5 ms. In this case, sever and client will disconnect randomly after 60 s to 45 mins they connect.

在后一种测试中，我将连接间隔更改为30ms。他们可以保持连接更长（超过10小时），但仍然脱离了。

I would assume if I leave the processor in idle state, everything should handle by BLE stack automatically and sending empty to keep the connection should have nothing to do with my application code. Also, I not have any application activity at the time they disconnect.

请帮我找到断开连接和如何提高连接稳定性的原因。

非常感谢。