https://devzone.nordicsemi.com/f/nordic-q-a/4455/pca10001-won-t-work-from-coin-cellMy PCA10001 was working(running the heart rate monitor example) from the coin cell. After it ceased to work, I assume the cell was flat, but on replacing it the PCA10001 still won&#39;t work unless powered via the USB cable. Any idea why this might be? Ien-USTelligent Community 13Fri, 14 Nov 2014 01:08:51 GMThttps://devzone.nordicsemi.com/thread/15828?ContentTypeID=1Fri, 14 Nov 2014 01:08:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:70321ba8-c810-49d4-a4d4-8ba4f2dd23c8JohnBrown<p>OK, I&#39;m an idiot. I cut the link to perform current measurement and then placed a jumper on pins 3 and 4 rather than pins 1 and 2. Sorry for wasting anybody&#39;s time.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/15827?ContentTypeID=1Fri, 14 Nov 2014 00:42:38 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a5122512-d8e6-4566-aed6-045295e8e700JohnBrown<p>There is around 3V2 ocross GND and VCC on P6, with or without the USB connection, so I guess the diodes are working OK, but even the blinky code won&#39;t work unless the USB cable is connected. The HRS example refuses point blank to connect with the Android RF Toolbox now, although the Nordic_HRM is listed, if you try to connect it says &quot;Error on discovering services (129). I suspect the PCA10001 is broken.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/15826?ContentTypeID=1Thu, 13 Nov 2014 20:08:57 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e97a9efa-cd44-497e-a081-e7715a10380aLocky<p>First items to check would be to assure that D1B is working properly, passing the Coin Cell voltage to the VCC_IO and VCC_nRF rails.</p><div style="clear:both;"></div>