Nexus 5X connection interval

Question

Hi, 
 Has anyone test with Nexus 5X ? 
 I could not change connection interval 7.5ms, the interval is always 45ms. 
 Does anyone know how to change the connection interval ? 
 Best Regards,
Joy Kang

endnode · Accepted Answer

Hi Joy Kang, 
 All phones (Android, iOS and I suppose also any other rich OS) are primarily tested with one (or narrow range of) connection intervals in BT LE GAP Central role. Only once Google release mint Android FW for Nexus device with 7.5ms connection interval: very first (factory) image of Android 4.4 for Nexus 5. Since then they realized (obvious thing) that Central role doesn't scale in terms of parallel connections if you use very low connection interval values. So to be able to guarantee that core feature they fix it at 40~50ms range. Now even if you don't run more than one LE connection at a time these "low level" parameters of LE stack are fixed and not accessible from API exposed to your apps. And while it's not the best for throughput I believe it's good decision for interoperability reasons. 
 However you can find different forum posts and suggestions that if you fix PPCP (Preferred Peripheral Connection Parameters) on GAP Peripheral side with lower connection interval than 40~50ms, then some phones use as low interval as 20ms. Unfortunately there are cases (HW + OS build combinations) which simply drop connection under these conditions. 
 To summarize it: for particular phone (if you care only about one or few handsets with given OS release) you might be able to "force" lower intervals from GAP Peripheral side but unlikely very low values such as 7.5ms. In general you should rather accept default values in 40~50ms range. 
 Cheers Jan

Nexus 5X connection interval

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