https://devzone.nordicsemi.com/f/nordic-q-a/44916/uart-moduleHello. I have been working with the nrf525840 dongle using SDK 15.2.0 trying to build a UART Service. I used the ble_app_uart example project that comes with the SDK and it worked well. I tried transferring the UART part of the program to the ble_app_blinkyen-USTelligent Community 13Mon, 18 Mar 2019 13:20:33 GMThttps://devzone.nordicsemi.com/thread/176729?ContentTypeID=1Mon, 18 Mar 2019 13:20:33 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d0f7259f-3b46-46cb-8678-e5c51b5feb1aJ&#248;rgen Holmefjord<p>Hi,</p> <p>Are you implementing hardware UART for the device? Note that the default UART pins in the SDK examples are using GPIOs P0.05 to P0.08, while some of these pins are <a href="https://www.nordicsemi.com/DocLib/Content/User_Guides/nrf52840_dongle/latest/UG/nrf52840_Dongle/hw_button_led">used for other components in the dongle</a>. If you get communications errors in the uart_event_handler, I would expect that one of the pins are in a state where a UART line error is detected. If you do not use HW UART, I would recommend that you remove all function calls related to app_uart library in your application.</p> <p>Best regards,<br />Jørgen</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/176498?ContentTypeID=1Fri, 15 Mar 2019 16:10:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e1206a39-e41a-42b0-b4a8-aff9809fefa4Eugene0469<p>Yes i did. This is what led me to change the NRF_SDH_BLE_GATT_MAX_MTU_SIZE from 23 to 247</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/176493?ContentTypeID=1Fri, 15 Mar 2019 15:42:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c1da7788-a4ce-4e24-8d98-d5d0dd2b56e2awneil<p>Have you checked&nbsp;<span>BLE_NUS_MAX_DATA_LEN ?</span></p> <p><span></span></p><div style="clear:both;"></div>