Seeking an nRF51 or nRF52 working application (S130) with observer callback

[Solomon]

Where can I find a working application that has an observer callback function (not a beacon) . this application must have also the broadcaster callback function.

[Petter Myhre]

Please have a look at the ble_app_hrs_rscs_relay example in the ble_central_and_peripheral folder in SDK 11. This example on GitHub may also be of interest, it is made for an older SoftDevice and SDK though.

[Petter Myhre]

It is advertising (broadcasting) and scanning (observing). If this is not what you need, could you elaborate a bit?