https://devzone.nordicsemi.com/f/nordic-q-a/4787/long-running-taskHi, I have following use case. The write operation on one of the characteristics triggers some UART job which takes about 1 / 1.5 seconds to complete. After the completion, results are sent through notification by use of ble_gatts_hvx method. Thisen-USTelligent Community 13Thu, 11 Dec 2014 14:18:10 GMThttps://devzone.nordicsemi.com/thread/16958?ContentTypeID=1Thu, 11 Dec 2014 14:18:10 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f139447a-1d3c-473e-902a-f7424a57daa7Stefan Birnir Sverrisson<p>Anything that is put into the <a href="http://developer.nordicsemi.com/nRF51_SDK/doc/7.1.0/s110/html/a00014.html">scheduler</a> queue executes in the main function, i.e. with the lowest priority. The BLE softdevice (BLE stack) runs with the highest priority so any application interrupt can not interrupt the softdevice.</p> <p>Do you get any error message when you call ble_gatts_hvx?</p> <p>What code template are you using? There is one available <a href="https://github.com/NordicSemiconductor/nrf51-UART-examples/tree/master/app_uart_library_example_with_ble">here</a> for the UART and BLE.</p><div style="clear:both;"></div>