https://devzone.nordicsemi.com/f/nordic-q-a/66255/uart-rx-issue-in-mcu-power-1-8vHi I am now working on a project which I use ble_app_uart_c as a reference. SDK 16 and used softdevice s140. UART works normally at 3.3V. But if I lower the power by 1.8V, it can be UART TX but not RX. The 1.8V TX signal is working well fromen-USTelligent Community 13Thu, 24 Sep 2020 00:45:01 GMThttps://devzone.nordicsemi.com/thread/271206?ContentTypeID=1Thu, 24 Sep 2020 00:45:01 GMT137ad170-7792-4731-bb38-c0d22fbe4515:ff4203ee-39ec-45cc-8b36-92568bad1fabMr.Chu<p><span>Hi,</span></p> <p><span>Thank you.</span></p> <p><span>I think the Uart Rx Port broke down while we were doing the Hardware Debugging Test. </span></p> <p><span>The problem was solved with the new MCU.</span></p> <p><span></span></p> <p><span>Best regards,</span></p> <p><span>Chu</span></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/271073?ContentTypeID=1Wed, 23 Sep 2020 11:58:16 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4e99182e-98fc-45b0-a63c-fc9ee0eb8a5cJ&#248;rgen Holmefjord<p>Hi,</p> <p>Which voltage is the device you are interfacing with over UART running at? If the voltage level difference gets outside the <a href="https://infocenter.nordicsemi.com/topic/ps_nrf52840/gpio.html#unique_637624999">input-high/input-low voltage levels of the GPIO peripheral</a>, the communication may not work correctly without a level converter. This is also the case for the device on the other end of the communication. You should check the datasheet of that device as well, to make sure you are within the specifications.</p> <p>Best regards,<br />Jørgen</p><div style="clear:both;"></div>