https://devzone.nordicsemi.com/f/nordic-q-a/13953/cannot-send-data-after-rtc-wake-upHi, I use S110 to develop a product which will send data to master every 30s. I registered a 30s App timer at RTC1. When this event occurs, I can control the IO pins but cannot send out any data. Do I need to turn on the radio first before sending dataen-USTelligent Community 13Thu, 19 May 2016 10:55:55 GMThttps://devzone.nordicsemi.com/thread/53298?ContentTypeID=1Thu, 19 May 2016 10:55:55 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5a81a910-8497-4b6f-82c5-2fba0171c4d4Ole Bauck<p>Are notification on the RX characteristic enabled? This is normally done by the central. If notification is not enabled <code>ble_nus_string_send(..)</code> will return <code>NRF_ERROR_INVALID_STATE</code>. Can you check the return value of <code>ble_nus_string_send(..)</code>?</p><div style="clear:both;"></div>