bt_att: att_timeout: ATT Timeout for device for Notify, after adding the one more characteristics

Question

I have created 4 Custom services, each service has below characteristics. 
 Service 1 - Total 21 characteristics 
 Service 2 - Total 5 characteristics 
 Service 3 - Total 3 characteristics 
 Service 4 - Total 2 characteristics 
 In Service 2 - One of the characteristics is having Read and Notification , I am using while loop to send bigger size data in terms of 1990 bytes for each notification. It is working without any issue. 
 Now added one extra characteristics in service 1 - So Total 22 characteristics in service 1. 
 Now Notification of Service 2 characteristics is sending data but getting error as bt_att: att_timeout: ATT Timeout for device after some time. 
 Please help to resolve this issue. 
 Using Zephyr SDKs v2.5.0 version

alberteinstein · Accepted Answer

the bt_att: att_timeout: ATT Timeout for device error may occur when the peer device sends an unexpected ATT request or when the connection parameters are not optimal for the notification frequency. You may want to check the following things: 
 Make sure that the peer device is not sending any ATT requests while you are sending notifications from Service 2. You can use a tool like nRF Connect to monitor the ATT traffic and see if there are any conflicts. 
 Try adjusting the connection parameters to reduce the latency and increase the throughput. You can use the bt_le_set_param API to change the connection interval, latency, and timeout values. You may also want to enable the CONFIG_BT_DATA_LEN_UPDATE option to increase the maximum data length. 
 iq test

bt_att: att_timeout: ATT Timeout for device for Notify, after adding the one more characteristics

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