https://devzone.nordicsemi.com/f/nordic-q-a/583/i-can-not-re-program-the-nrf51822-whyI have uploaded the following code, but I can not re-program the next. #define AREF0 0 #define AIN3 2 #define AIN4 3 int main(void) { // Start 16 MHz crystal oscillator NRF_CLOCK-&gt;EVENTS_HFCLKSTARTED = 0; NRF_CLOCK-&gt;TASKS_HFCLKSTARTen-USTelligent Community 13Thu, 03 Oct 2013 10:23:21 GMThttps://devzone.nordicsemi.com/thread/3027?ContentTypeID=1Thu, 03 Oct 2013 10:23:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8e089030-40cb-4361-be8f-82a9dbd65a6dPeter<p>Thank you very much! :D It works. :D</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/3026?ContentTypeID=1Thu, 03 Oct 2013 10:14:31 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2700b262-ce06-4532-aa8e-8d276c1fa52cHung Bui<p>Hi Peter,</p> <p>You need to wake the chip up before you can program it. The programmer can not wake it up when it entered System off mode.</p> <p>What you can do is to use nRGo Studio to recover the chip, you should be able to program it again after that.</p><div style="clear:both;"></div>