https://devzone.nordicsemi.com/f/nordic-q-a/1878/the-documentation-is-a-bit-vagueI&#39;m implementing my own equivalent of hci_dfu_send_hex; There is not enough information in the documentation on how these packets are constructed. I found that the first packet (prep flash) sent by hci_dfu_send_hex to the bootloader has an ACK counteren-USTelligent Community 13Thu, 13 Mar 2014 19:40:31 GMThttps://devzone.nordicsemi.com/thread/8111?ContentTypeID=1Thu, 13 Mar 2014 19:40:31 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b525f266-bfd9-44b4-a62e-d67726b7e296RG<p>Thanks Ole, got it working; solved the problem last night. best Radu</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/8110?ContentTypeID=1Thu, 13 Mar 2014 15:31:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a61210c5-0f4d-4fcf-861a-61b23ddb5e25Ole Morten<p>I think most of what you need to know should be covered by <a href="https://devzone.nordicsemi.com/index.php/i-would-like-to-have-an-example-about-hci-packet-format">this question</a>, so I suggest you take a look at my answer there. In general, I&#39;d recommend to keep the Core spec ready when implementing this on your own. :-)</p><div style="clear:both;"></div>