How to make GATT client aware of changes to a characteristic?

[john kotkin]

Hi,

I trying to write an application with android for my nRF51822 device I use Battery service example but every time i update battery level i need to request for changed value from my android program, how to make battery service example push updated value to the air?

[Victor Nascimento]

For this you have to use a Notification / Indication. Please have a look on the UART example. The TX characteristic has notification properties. On the App side, you have to subscribe to a particular characteristic and you will get an event callback whenever the BLE module writes to that characteristic.

[john kotkin]

If you mean this part hvx_params.type = BLE_GATT_HVX_NOTIFICATION; i can see it's notification on ble_bas.c service file but still i can get notification on change