BLE disconnect issue

[Peng]

Hi all,

We are using nRF51822-QFAA-R7 to develop our HUD system. The BLE connection is not stable some time.

For most iphone 6/6s, the BLE can connect for a short time (1-2s) and disconnect and reconnect for (1-2s).

We tested one iphone 5 and one iphone 5s, the connection has no problem.

Some time when the charging cable connected, the connection is unstable

Some time when the LTE and wifi turn off will help, but not quit repeatable.

Some time power cycle the whole HUD system (include the BLE) will help to get a stable connection.

We are using typical balun to match the impedance.

Signal level is not an issue. We tried to change the amplitude on receiver from -80dBm to -30dBm, but it doesn't make any difference.

The FCC report shows that our peak frequency is a little bit offset: 2.40214GHz. Would this be an issue?

The external crystal we are using is Epson crystal www.mouser.com/.../

It is 10ppm component.

I would appreciate a lot if there is any suggestions.

Thanks!

Peng

[Peng]

The load capacitors were 7pf, I did changed them to 15pf today, but status is still the same...

I was using lightblue to test the device, the BLE connection can be found by iphone, and the request to pair window pops up, if I don't click the pair button, the device can still transfer data to the iphone. After I click the button, after 4-5 second, a window will pop up and shows that "Disconnected Alert", and the status will be "Disconnected. Data is Stale"

We don't have 32KHz source in the design.