https://devzone.nordicsemi.com/f/nordic-q-a/15449/using-sd_ble_gatts_hvx-in-timer1-interrupt-service-cause-the-hardfaultCondition: nRF52, SDK11,s132, SDS v2.0. Using the sd_ble_gatts_hvx() in timer1 interrupt service(timer1 interrupt priority is set to level 3) will result in hardfault. While, using the sd_ble_gatts_hvx() in main loop will not cause any error. Why? Howen-USTelligent Community 13Mon, 01 Aug 2016 10:23:29 GMThttps://devzone.nordicsemi.com/thread/58975?ContentTypeID=1Mon, 01 Aug 2016 10:23:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:29d77719-7f6e-49b0-bd2b-cddd60aace8fSusheel Nuguru<p>I am accepting this because this has been discussed many times and the answer is very accurate.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/58974?ContentTypeID=1Sun, 31 Jul 2016 11:49:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0e341dc6-a36b-4511-85bb-7baea3de9d76RK<p>This gets discussed multiple times a week. You can&#39;t call SVC calls from an interrupt level higher than the SVC interrupt and all sd_ functions are implemented with SVC calls. If you do the cortex hardfaults. Interrupt level 3 is higher than the SVC interrupt level so either you make your timer interrupt lower priority or you bounce it to a lower priority level (eg main thread) and process it there.</p><div style="clear:both;"></div>