https://devzone.nordicsemi.com/f/nordic-q-a/11775/nrf8001-w-o-uart-connected-howI have a custom board designed which implements a Arduino Micro (ATmega32U4) and an nRF8001 chip based upon Richard Clarks&#39; nRF8001 breakout . The Arduino FW uses a slightly enhanced version of RedBear&#39;s nRF8001 library which in turn calls lib_aci() Nordicen-USTelligent Community 13Mon, 08 Feb 2016 04:20:42 GMThttps://devzone.nordicsemi.com/thread/44515?ContentTypeID=1Mon, 08 Feb 2016 04:20:42 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5e5ce1d1-b7d8-4dfe-8438-03c761e0d9b0Zittware<p>Turns out I was right on the money. When I &quot;disconnect&quot; the usb port via software; there must be a glitch on my powersupply which results in unexpected issues. I didn&#39;t put a scope on it; but powering this with an external supply resolved my issue. It goes right into BLE mode as I expect.</p> <p>Closing as not-a-bug / issue.</p><div style="clear:both;"></div>