https://devzone.nordicsemi.com/f/nordic-q-a/40419/some-ideas-about-the-gap-parameter-in-sdkWe found the devices developed with nrf51 and nrf52 will disconnected from the iphone sometimes, and we can&#39;t find the real reason. I study the gap parameters on nrf51 and nrf52 sdk, found the default value: #define APP_TIMER_PRESCALER 0 /**&lt; Valueen-USTelligent Community 13Wed, 14 Nov 2018 08:16:46 GMThttps://devzone.nordicsemi.com/thread/157223?ContentTypeID=1Wed, 14 Nov 2018 08:16:46 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fd842be7-b019-462b-939e-c4a0c2648574zk017<div class="trans-left"> <div class="trans-input-wrap"> <div class="input-wrap" dir="ltr"> <div class="textarea-wrap without-textarea-bg"> <div class="textarea-bg-text" id="textarea-bg-text">Hung Bui, thank you for your answer. my application on iphone is running on the foreground. The appearance of disconnect phenomena is not regular， it&#39;s diffcult to trace. &nbsp;we will try to trace it.</div> </div> </div> </div> </div><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/157104?ContentTypeID=1Tue, 13 Nov 2018 13:54:19 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5bb717c6-df30-4e6f-a55d-bebadf3f5c5fHung Bui<p>Hi zk,&nbsp;</p> <p></p> <p>I don&#39;t&nbsp;think that would be the reason the iPhone disconnect. Even if you have preferred connection parameter that doesn&#39;t match with the guideline, the phone will just ignore it.</p> <p>How long did it usually take until the phone disconnect ? Do you have your application running on the foreground when disconnection happened ? The phone may disconnect if it&#39;s a background application with no activity. Do you see the same problem when testing with one of our example ?&nbsp;</p> <p>Could you capture a<a href="https://www.nordicsemi.com/eng/Products/Bluetooth-Smart-Bluetooth-low-energy/nRF-Sniffer/"> sniffer trace ?</a>&nbsp;</p><div style="clear:both;"></div>