https://devzone.nordicsemi.com/f/nordic-q-a/12271/mbed-why-can-p0-00-not-be-used-as-an-analoginWhile both P0.00 and P0.01 has Analog Input function, initializing an AnalogIn (in mbed) with P0.00 will cause the firmware to fail to start at all; but initializing using P0.01 does not cause any issue. Why is this the case? Is it because P0.00 isen-USTelligent Community 13Wed, 02 Mar 2016 09:41:01 GMThttps://devzone.nordicsemi.com/thread/46392?ContentTypeID=1Wed, 02 Mar 2016 09:41:01 GMT137ad170-7792-4731-bb38-c0d22fbe4515:70dd4e7a-8c13-4be2-95ae-09e2efd38a4fOle Bauck<p>P0.00 is ADC reference input and not an ADC input. AIN0-AIN7 (P0.26-P0.27 + P0.01-P0.06) are the ADC inputs you can choose from, see <a href="http://infocenter.nordicsemi.com/pdf/nRF51822_PS_v3.1.pdf">Product Specification</a> chapter 2.2. AIN0 and AIN1 is also used for 32KHz crystal, so if these shall be used the 32KHz crystal must be diconnected first.</p><div style="clear:both;"></div>