Why am I seeing an LL_REJECT_IND from the slave intermittently?

[Eliot Stock]

I have an nRF51822-based peripheral using the SoftDevice 110 v7.0.0 and SDK v6.0.0. The peripheral uses two custom characteristics under a single custom service. I'm using the Device Manager. The central is an Android app using the new Android L preview BLE stack.

About half the time the central attempts to connect to the GATT server, discover services, and bond, the connection is immediately dropped. Here's a Wireshark screenshot and log of when that happens.

screenshot_wireshark_reject.png

ll_reject_ind_2014-08-29.pcapng

And here are my security parameters:

// Timeout for Pairing Request or Security Request (in seconds).
#define SEC_PARAM_TIMEOUT                 30

// Perform bonding.
#define SEC_PARAM_BOND                    1

// Man In The Middle protection NOT required.
#define SEC_PARAM_MITM                    0

// No I/O capabilities.
#define SEC_PARAM_IO_CAPABILITIES         BLE_GAP_IO_CAPS_NONE

// Out Of Band data not available.
#define SEC_PARAM_OOB                     0

// Minimum encryption key size.
#define SEC_PARAM_MIN_KEY_SIZE            7

// Maximum encryption key size.
#define SEC_PARAM_MAX_KEY_SIZE            16

I'd say this happens about a third to half the time. The rest of the time the connection is fine. Why is this happening? How do I debug this?

[Edit]

Here's the log from nRFLogger/MCP app on Android L:

mcp_log_disconnect_2014-09-02.txt

[Hung Bui]

Hi Elliot,

Could you open a support case and refer to this thread in the case? We may need your source code for further investigation. Which phone did you use to test ?

Btw, could you reproduce the issue with our SDKv6.0 example, such as the ble_app_proximity ? And which app did you used on the phone side ? We would suggest you to use the Master Control Panel app.