We are using an nRF51822 with s110 v5 and an iPhone. When the iPhone connects to the nRF51822, occasionally (perhaps 1/4 of the time) the iPhone fails to complete service discovery.
We have tried looking at what is going on over the air with a BLE protocol analyzer. The transactions look like this: connection event 0 iphone -> nRF LL Version Ind connection event 1 iphone -> nRF ATT Exchange MTU Req nRF -> iphone LL Version Ind connection event 2 nRF -> iphone ATT Exchange MTU Response connection event 3 iphone -> nRF ATT Read by Group Type Req
If the service discovery is to be successful, the nRF replies with: connection event 4 nRF -> iphone ATT Read by Group Type Response
However, when the discovery fails the nRF does not reply to the Read by Group Type Request, and the connection intervals from event 4 onwards are empty.
As far as I can see, it is the nRF that is failing to behave correctly, not the iPhone. Is there something we could be doing wrong in our firmware, or some way of debugging this in more detail?
Thanks Dan
