https://devzone.nordicsemi.com/f/nordic-q-a/1889/nrf51822-supply-by-rx-pinHi all, When I test the UART demo progrem, I cut off the power supply of the board,but the RX pin is still connected to the PC TX pin,and I measures a voltage on the VDD pin of nrf51822,and the nrf51822 is on work, does it can supply the nrf51822 byen-USTelligent Community 13Fri, 14 Mar 2014 11:38:26 GMThttps://devzone.nordicsemi.com/thread/8143?ContentTypeID=1Fri, 14 Mar 2014 11:38:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:14a8eab9-3b7c-4cf9-9ca9-8634872a9059H&#229;kon Alseth<p>Hi,</p> <p>Spec-wise, the maximum input voltage on a IO is VDD +0.3V, meaning that it is not within specifications to have &gt;0.3V on an GPIO when VDD is 0V.</p> <p>So, no: you cannot supply VDD on any pin.</p> <p>Best regards Håkon</p><div style="clear:both;"></div>